Introduction

Many of us experience eyestrain, eye pain, headaches, and/or worsening vision after using display technology for many hours as part of our personal and professional lives.

We can cure our eyestrain issues within days by dropping our phones and tablets, getting away from our televisions and computers. Using only sunlight in the day, and fire at night.

The human body evolved to suit these conditions for tens of thousands of years, and the body will expect these conditions for thousands of years to come. Problems emerge as our environment abruptly changes with the introduction of lighting and display technologies. These problems include eyestrain and myopia.

Abstaining from modern lighting and display technology is not practical for most of us. We who have significant adverse reactions with the technology, and are able to identify the technology as the source of the problem, are a small minority of consumers. Therefore, the mass market has little incentive to make changes to relieve our problems.

Myopia involves more permanent changes to the eyes, and as with most conditions, it's much easier to prevent than cure. Unfortunately, there is more incentive in the free market for people to have poor vision than to have good vision, since there is more to sell someone with poor eyesight than someone with good eyesight. Therefore we can not expect preventative measures to be promoted in the mainstream.

The purpose of this page is to document the observations, experiences, and discoveries I've made throughout the years in my struggle against eyestrain and myopia, to help those with similar issues find solutions. I was able to not only alleviate all my eyestrain symptoms while using a display, but also actually restore significant visual acuity. My experiences and reactions are not going to be identical to yours, since these details of human physiology can vary wildly, but I do believe that there will be significant areas of commonality between us, and that you will find helpful information here.

The information on this page is not medical advice and is not intended to replace the care of professional eye specialists. Please get your eyes examined regularly, since many conditions which can lead to blindness are treatable if identified in the early stages.

Quick Guide to Eyestrain Elimination & Vision Improvement

- follow good vision habits, especially active focus.

- do not wear your corrective lenses, or use the weakest prescription possible while using your display / while doing close work.

- when reading, make text size as small as possible, and/or move yourself away from the image as far as is practical.

- eliminate extreme differences in contrast in your environment and content.

- eliminate flicker from your display and environment.

- minimize blue light as well as ultraviolet from your display and environment.

- introduce infra-red light to your display and environment.

Vision Habits

The percentage of your waking hours spent practicing good vision habits or bad vision habits will determine whether your eye sight will improve or worsen, and how quickly. Without consciously keeping track of your behaviours it's very easy to underestimate the amount of time spent conducting your eyes in damaging ways.

Bad Habits:

- Close work: This includes wearing corrective lenses which bring the focal point closer than required for the current task.

- Squinting: The process of narrowing the opening of the eyelids which temporarily improves visual clarity by cutting out many of the light rays entering the eye which are not parallel with the visual axis. For those familiar with photography, it's a similar concept to shrinking the aperture size, which increases the "depth of field". It is best to avoid squinting since eventually you will be relying on it rather than your eye's natural resolving functions.

Another type of squinting can be called "brow squinting" where one lowers the angle of their head such that their line of sight runs very close to the edge of their brow. I have found myself doing this unintentionally, and have found it equally harmful as normal squinting. This is easier to do when your monitor is located too high. The top edge of your monitor or television's screen should not be higher than the horizon if you are sitting upright.

- Scanning: This is the process of tracking the eyes across the content constantly without stopping to focus on it. Reading text with a font size which is too large allows the reader to scan without actually focusing. I've found that I tend to scan more with certain activities than others, for example with online shopping, where I'm mostly scanning the images until something catches my eye. It's important to consciously stop yourself from scanning.

- Staring: fixating for long periods is harmful because the eye is getting used to long intervals of not re-acquiring the image. Particularly harmful is staring into empty space, not on any particular detail. The eyes should not be in constant motion, which is what scanning is, but should move the focal point frequently to other locations.

Good habits:

- Maximizing focal length: Myopia is closely tied to close-work so avoiding close focus is imperative to stopping its progression and reversing it. Positive lenses, i.e. reading glasses can be tremendously helpful since they move the focal point further away.

- Active focus: This is one of the most important habits for recovering your vision. Stop scanning and focus on a point, changing that point frequently. Try to focus on the tiniest details possible - the finest tree branches, the serif on the letters you are reading, the most distant point down the road.

- Blinking often: Keeping the eyes moist is important. Also, the more frequently the eye is forced to re-acquire the image, the better it gets at it.

- Look outside: Hopefully you have a window in your work environment which you can look out of to relax your eyes. If not, find the furthest possible point to look away to. I've found it helpful to put a mirror just beside my monitor, which I can quickly glance to for more distant focus. Make a habit of looking away from the screen every few minutes.

I thought that I would reverse my myopia simply by moving the focal point far away while I work - by getting a large format LCD monitor and using it from several feet away. However, I continued with the other bad vision habits, so no improvement was made, It probably did slow progression of myopia, compared to if I were using a normal monitor at arm's length. Another hindrance is the inherent flicker of the monitor, which made my eyes not want to focus on the image, which kept them in a scanning state.

Close Work & Myopia

Not all who do close work develop myopia, but almost all who develop myopia have spent much time doing close work. Humans and our evolutionary predecessors relied primarily on their sight to survive, so those who would lose their visual acuity would quickly be weeded out of the gene pool. There is a genetic component - let's call it "adaptability" of the eye. Some people have adaptable eyes, others do not. It is the environmental condition of close work which causes the eye to adapt to the myopic state and long durations of close work which cause it to remain there. The condition would not manifest itself in the natural human environment. Therefore, these "eye adaptability" genes did not get filtered out.

The eye is in its relaxed state while looking in the distance - the lens is at its flattest. Then when looking up close, the ciliary muscles compress the lens to thicken it to its roundest, maximizing the refraction. Any muscles that are used extensively will get bulkier and stronger, and change their relaxed state - picture a weightlifter's elbow that remains bent in its relaxed state due to the bulk of connecting muscle - this is partly what is happening with myopia. The other part is the elongation of the eye. These processes are referred to as "accommodation".

Compressing a muscle takes energy. Living things are always looking for ways of minimizing energy consumption. Our physiology is recognizing that we are in this state of muscle compression for long periods, so the physiology responds by paying the "one time fee" of elongating the eyeball - now the eye has accommodated the closer focal point, and the eye muscles need not strain as much while looking closely. The problem for myopics is that the eye has adapted to this new state with permanence.

A note regarding close work and lighting conditions: It is a widely held belief that reading in the dark is harmful. This is correct - at least for those with adaptive eyes. It causes/worsens myopia because in a darker environment the pupil opens wider, the eye's lens must be compressed more to bring close things into focus than in a well-lit environment, when the "pinhole" of the smaller pupil shuts out many of the non-parallel rays, eliminating much of the need for lens compression. This is also why some people's vision is blurrier under flickering lights - because the pupil "settles" in a state between the light and dark phases of the flicker, in which it is wider than if under constant lighting of equal brightness. For this reason doing close work under flickering light is almost as harmful as doing it in the dark.

Understand that myopia is not weakness of the eye, but over-strengthening of it - the eye is refracting too much, limiting the focal range to near objects. And what do corrective lenses do? Virtually bring the objects closer!

Excellent presentation on myopia:
https://www.youtube.com/watch?v=x5Efg42-Qn0

Corrective Lenses

A large and increasing percentage of people today wear corrective lenses for myopia. This is mainly due to the increase in time being spent doing close work. While the lenses allow the wearer to see clearly in the present, they damage the eyes in the long-term, often permanently.

The lenses are convex, causing light rays to diverge. The only thing the lenses do for myopics is move the focal point of the object being looked at closer to the viewer - into the range that the abused eyes can still see sharply at.

The eyes eventually accommodate to the prescription lenses, and the wearer no longer sees clearly while wearing them. A trip to the optometrist later, and the wearer now has a stronger prescription. This cycle repeats over the years, leaving the wearer totally dependant on corrective lenses.

Stronger prescriptions increase strain on the eye further, leading to complications. Floaters commonly form. The deformed eye is also susceptible to a new range of dangers - retinal detachment is a serious risk for those with extreme prescriptions.

Reversing myopia is difficult. For those who wear strong prescriptions, even more so. Recovering visual acuity starts with maximizing the focal length that your eye is working at. Prescription lenses are typically set to have distant objects in sharp focus, but if you are spending most of your day at arm's length from a screen, the prescription is too strong. Order a weaker pair specifically for use at the desk, or use an older/weaker pair if possible. If you wear contacts, get a pair of reading glasses from the drug store / dollar store and wear them while doing close work. The ideal strength is such that whatever you are looking at is just at the point of blurring. Once at this point you must practice good vision habits especially active focus.

Many activities involve a mix of close and distant focus, for example: Driving - looking between the outside and the dashboard. School - looking between the board and your notes. If your uncorrected vision is good enough to do close work, I suggest getting narrow frames for your corrective lenses which are rimless on the bottom. These will allow you to easily look below the lens when doing the close focus part of your activity.

A quick fix to poor vision would be nice. You might consider laser surgery, where the cornea is modified into functioning as a corrective lens, but this keeps the eye in the myopic state permanently with the associated risks mentioned above, not to mention the risks/complications of the surgery itself. Further, continuing with bad vision habits after such surgery will likely get you back to needing prescription lenses within a few years, only now you are a few thousand dollars poorer, and your eye is an even more strained state. Every person I know personally who has gotten corrective laser surgery was back to wearing glasses within a decade.

Knowing this, the "hard way" seems to be the way to go. The good news is that your eye wants to see clearly, and if it's treated well it will recover.

Positive Lenses

Positive lenses, known commonly as reading glasses are an essential tool in preventing and reversing myopia.

Positive lenses are convex, like a magnifying glass, they cause light rays to converge. The effect of this is moving the focal point of the object you are looking at further away.

Positive lenses should be worn by those with "adaptive eyes" while doing close work to prevent progression of myopia. It is important to select a strength which keeps the content being viewed just at the edge of being blurry.

It's easy to unconsciously move closer to the content you are viewing - this will largely negate the benefit of wearing the reading glasses. Be vigilant!

Reading glasses are widely available without prescription at pharmacies, dollar stores and other variety stores. They can be found in the handbag or shirt pockets of the elder generations since the eyes often have trouble with close focus in older age (a condition called presbyopia).

Since the eye tends to try resolving a blurry image, positive lenses can be used in a form of therapy where they are worn for extended periods. I have found that my vision seems sharper after spending around 20 minutes wearing the glasses, looking out the window while blinking often, trying to focus. I did this while riding the bus in my college days. Overall, the time that can be spent doing this is only a tiny percent of your waking hours. To recover eyesight, the majority percent of one's waking hours must be spent practicing good vision habits.

Pinhole Glasses

Pinhole glasses are similar to sunglasses, except that the lenses are made of opaque material with a regular pattern of perforation. Hole size is around 1mm. Donning the glasses allows the wearer to immediately see objects through the pinholes with considerably improved sharpness, regardless of their need for corrective lenses. This works since the pinholes are only letting in the rays of light which shine in-line with the eye's axis - the eye's focusing mechanism is largely bypassed. Similar to how the bad vision habit of squinting works.

Claims are made that long term use of the glasses can improve vision. They can be bought from Chinese e-retailers, specialty stores, or even made at home with an opaque plastic sheet, a hole puncher, and lots of patience. Perhaps you can find some salt-shaker caps with small enough perforations to try out the effect.

I bought a pair of pinhole glasses from Ebay to experiment with in 2013. Wore them for a few weeks in the evenings. I can't say that I saw any improvement while not wearing them - perhaps even the opposite. In theory, if all the glasses do is squint for you, then it seems unlikely that it could improve your vision, as covered in the article on vision habits, because active focusing (without squinting) is what in my experience has had the most positive effect. One possible benefit to the glasses is that they promote eye movement, since the wearer must move their eyes from pinhole to pinhole to see - breaking up staring habits, which are also linked to poor vision.

If you have floaters they will become more sharply defined while wearing the glasses.

Overall, I would say that they are worth trying. For people with bifocals or extreme prescriptions they may be handy just to take a break from those lenses. Possibly for rough outdoor expeditions where you would like to see, but don't want to risk expensive lenses being scratched/damaged/lost. They have the added advantage of not being able to fog-up or get smeared with oils. Not recommended and probably not legal for use while driving, and also due to the amount of light blocked, their usefulness lessens as it gets dark.

Sleep & Exercise

I have noticed that my vision tends to be best on Fridays, after a work week of getting a bit less than 8 hours of sleep per night. Then on the weekend after sleeping-in my vision tends to be worse.

I recall one night years ago when I could not sleep at all, while I was still in the early stages of myopia - the following day my vision was effectively back to 20/20.

I'm not recommending to get less than 8 hours sleep per night, but I'm pointing out a pattern, which you may also have observed, and which ties into the topic of exercise.

I've noticed that my vision is worse when I have not had a solid work-out during the week. On the other hand I've noticed that my vision tends to be better the day after a good work-out. I believe it's because the body gets used to rebuilding a certain amount of muscle per night, and if there is little to re-build in the arms/legs/torso it will build on the muscles of the eye, which as explained in the article on close work, the myopic eye is already over-built.

So, taking these observations into account, to maintain good vision we should exercise regularly and not sleep excessively

Your experience may vary from mine since this is linked to metabolism, which varies greatly from individual to individual.

Contrast

The overall difference in brightness between the lightest and darkest parts of the displayed image being viewed can have a significant impact on vision. The difference in brightness between the display and the room environment can similarly impact vision..

Contrast in Content

You may have experimented with "high-contrast" themes in your device's operating system, which are designed for the visually impaired. These themes typically use white and other full-brightness colours for the text on a black background. This makes the text easier to read compared to black text on white background since it's easier for the eye to resolve the brightest elements than the darkest.

Some applications use similar color schemes by default: coding layouts, CAD applications.

Unfortunately, this acts as a "crutch", which the eye gets accustomed to, and then can no-longer resolve black text on white backgrounds as easily. Obviously, some people have no choice but to use these themes, but for those who can still read with normal themes, it is best to avoid becoming dependent on the high contrast themes.

Another side effect of reading bright text on a dark background is that the lines of text tend to "burn" into the retina more than the bright spaces between lines of dark text. This burn-in can persist for a while. I recall a couple of years back when I was reading a long PDF book and had overridden the document colours to be bright text on a dark background, the burn-in could last for hours after long reading sessions.

There is a case when I can recommend light text/dark backgrounds: if the display technology you are using is inherently offensive to your visual/nervous system, causing eyestrain/headaches, using a black background theme reduces the overall amount of the offending light, in the case of flicker, reduces the extremes between light and dark, making the flicker less irritating.

You have likely used hardware, browsers, or web sites with a "night mode". These may be okay to read for extended periods as long as the contrast is not too extreme.

Contrast in Room

Many of us will remember being told as children not to watch TV in the dark since "it will ruin your eyes". There is truth behind this, and a few factors at play. First is that the television in question was typically a CRT, which has an inherent flicker, and if it's the only light source in the room, the entire room will flicker along with the TV.

Second is that as the scenes on-screen change, their overall brightness can change dramatically. The eye's pupil follows along, frequently dilating/constricting. These extreme variations in brightness at short time intervals is not a condition that the human eye is well adapted to it. - many including myself get eyestrain/headache from darkroom viewing of "dynamic" content. A steady light in the room would lessen the pupil's activity - lights mounted behind the TV for this purpose are referred to as "bias lighting", and are often sold as kits of LED strips to be mounted along the rear perimeter of the display. (If considering one of these kits ensure that they are flicker-free and low in blue light emission, otherwise you will just be introducing another source of eye strain.)

Third is that only a small part of the field of view is being occupied by a bright object while the rest is dark. The retina is being used unevenly, but this is less concerning than the above since there are scenes in our evolutionary history with such great variation in contrast: watching a bright moon in the night sky, being in a cave and staring out the entrance, watching a fire at night.

Watching films/gaming in a completely dark room can definitely enhance the immersion, particularly with a high-quality display. Unfortunately it does inherently strain the eye more than viewing in a room with ambient lighting, so it should be done in moderation.

Text Size

Myopia is a slippery slope - the shortcuts we adopt to help us see in the moment worsen our vision in the long-term. One of those shortcuts is increasing the text size in our field of view.

Increasing text size can be as simple as moving our head closer to the page or screen we are looking at. The high-tech methods are equally harmful - increasing the browser or PDF zoom, increasing the font size in the word processor.

The bigger the text being read, the less the eye has to actively focus, the more one's vision can deteriorate. Text size is a function of the angular field of view (i.e. degrees) rather than absolute text size: 1cm size text read from 1m has the same size on the retina as 1m size text read from 100m away. Even if you were able to do your computer work on a cinema screen from the back row of the theater, if the apparent text size you are working with is considerably larger than the minimum your eye can resolve, your vision can deteriorate to the point where that text becomes the "edge" of readability.

Enlarging text allows the eyes to "scan" without actually focusing. The eyes get accustomed to this state, and will operate this way when not reading. The time spent not actively focusing is time spent losing visual acuity.

Further, the big text allows the eyes to be imprecise and slacken in convergence. Once the sharpness of your vision improves, you will likely notice frequent moments of "double vision" while trying to see finer details, because the eyes are accustomed to imprecision, they are actually pointing at two slightly different points, called convergence error - this should pass as the eyes are re-trained, but if not there are therapies available.

If you have the choice between reading the same screen with positive lenses from 1 foot away, or no lenses from 3 feet away, assuming both cases are at the edge of what is readable to you, choose to be further away, since the smaller size of text will re-train your eyes for convergence.

As a result of the proliferation of smartphones and other mobile devices, web developers are increasingly maximizing font sizes on their pages to suit the worst case viewer, i.e. a far-sighted person using a low-res or tiny screen. I believe we will see a sharp increase in the number of myopic individuals due to this.

Run through the options on your applications/devices and find the text size options. Browsers, e-mail apps, OS user interface: keeping these text sizes as small as is readable will accelerate your vision recovery.

ClearType

Once LCD monitors became popular in the early 2000's, many users found the hard pixel edges of text unpleasant to read. These hard edges were previously concealed by the softness inherent to CRT monitors. Anti-aliasing of text was one solution. However, due to the limited resolution of early LCDs, very small text which was anti-aliased looked blurry. Software engineers responded by introducing subpixel rendering, best known by Microsoft's branding, ClearType. Some software may not be specific about whether it is using subpixel rendering or not, and amy simply call the option "font smoothing".

Sub-pixel rendering works by taking advantage of the subpixel arrangement of LCD panels, most commonly RGB, adding coloured pixels to the edges of text where the active subpixel corresponds with the edge of the letter.

It should be noted that subpixel rendering is less likely to work with atypical subpixel arrangements, i.e. BGR, WRGB, or pentile. Also it is completely useless with displays not using subpixels, i.e. DLP projectors.

Reactions to ClearType are mixed. In my case, it seems to introduce eyestrain. This is definitely one of the things you should experiment with turning on and off to see how/if it affects you. Typically this is a setting in the Operating System, but many programs, PDF readers for instance, have their own separate setting. Some applications have it hard-coded in without option to disable it.

Negative reactions to ClearType may be related to the LCD panel's dithering and / or inversion processes. More about these in the article on LCD

ClearType rendering depends on colours, so a hackish way to disable it if all else fails is to turn the display's saturation all the way down to zero, either through hardware controls or in the software video settings.

With the introduction of UHD "4K" and higher resolution monitors, subpixel rendering becomes less and less necessary, since font pixel dimensions tend to be larger, standard anti-aliasing "blur" becomes negligible. As of 2019 it appears that ClearType is being phased-out of major operating systems / software suites, but its ghost will linger for many years in the form of screenshots taken with the feature active.

Motion

Motion on a display and motion in realty are two different things. Content on a display is delivered as a series of still images at a certain frame rate, whereas motion in the physical universe has an infinite "frame rate".

Motion in this context can mean anything from reading scrolling text on a web page, to full 3D gaming.

Our brains are able to interpret a series of still frames as motion, but our visual system has limits which introduce artifacts in how this motion is perceived. More on this in the article on motion perception.

What kind of display, and what refresh type is being used to watch motion can have a tremendous impact on eyestrain and myopia, since different display types, or even different models/configurations of the same display type can have widely varying characteristics. See the articles on display types, and motion enhancement.

Motion displayed in certain ways makes the eye unable to actively focus, and while the eye is not actively focusing, visual acuity is deteriorating. Therefore it's important to understand the limitations of display technologies and the content itself, and adjust behaviours accordingly, if maintaining/improvement of vision is the priority.

Room Lighting

We evolved to live in bright days and dark nights. Many of us are now living bright nights until just before sleep. This is proving to have detrimental effects on sleep, and likely too on eyesight.

I have noted that in periods when my evening room lighting was brighter, my vision overall seemed to worsen. I'm not sure why - perhaps the eye is expecting some "recovery time" in the evenings when it is not being blasted by photons. Or, perhaps by always being in a well lit environment, the eye slackens in its overall focus ability since it can rely on a constantly constricted pupil to see clearly, rather than the focusing mechanism of the eye.

We have to keep in mind our ancestors who only had the stars, moon, and fires to light things up by night.

As noted in the article on close work, doing close work in poorly lit environments causes and worsens myopia in susceptible individuals, so bright task lighting should be used. Ideally, close work is avoided in the evenings, and overall room lighting levels are kept low for optimal eye health and sleep quality.

As noted above, light quantity is one aspect to be conscious of. Light quality, i.e. the lighting technology used is equally, if not more important..

Incandescent

Incandescent/halogen lighting is the closest to fire of all the technologies. It emits the full spectrum of visible light + infra-red which seems to be critical for maintaining eye health.

Incandescent lighting works by running electricity through a thin filament of resistive material, typically tungsten. The resistance causes the filament to heat up and glow white-hot which is the source of light. The filament continues to glow for a short time after power is cut, so flicker caused by modulation in power, i.e. alternating current (AC), is minimal compared to other light types. See external links below for a video showing a light bulb recorded with a high speed camera.

Unfortunately, some people, especially those already sensitized by other lighting types, are sensitive enough to be bothered by the AC flicker, particularly in Europe and other lands where the mains frequency is 50 Hz. In that case it is best to use a lamp running on DC power - low voltage Halogen lamps are more commonly designed this way, but be wary of dimmers since most of them use pulse width modulation for dimming, which in effect re-introduces flicker.

The main disadvantage of incandescent lighting is the high energy consumption - the energy is released in the form of heat, which can be undesirable, particularly in a confined space which is already warm.

A note regarding Halogen lighting: as these are more energetic / efficient, they emit more ultraviolet light than the standard incandescent bulbs. Halogen bulbs are made of quartz to withstand the higher temperatures involved, and quartz does not block ultraviolet light (unlike the glass used in a normal incandescent bulb). Ensure that the UV light is being filtered somehow if you are using halogens for evening lighting.

Most fixtures for halogens come with a glass disc UV filter in front of the bulb. Some bulbs are coated to block UV, but assume that they are not if you don't have specific info about the bulbs you are using.

Fluorescent

Fluorescent lighting works by electrically exciting the mercury vapour within a sealed tube to the point of discharge. This discharge is typically in the form of UltraViolet light, which then hits the "fluorescent" phosphor coating of the tube, which emits the visible light. This type of lighting inherently flickers since the "sparking "inside the tube happens at a certain frequency, ranging from mains 60/50 Hz, to over 30 kHz with newer electronically ballasted lamps.

Fluorescent lighting is available in tube and compact (CFL) formats. Lighting characteristics do not vary much between the two formats.

Due to the inherent flicker of these lights, a room lit solely by fluorescent is actually much darker than it appears to be since the lights are off during the dark phase of the flicker - most humans are not able to perceive this due to the way we perceive motion, however the light that is hitting the cornea, iris, lens, retina, and entering the optic nerve is flickering. Vasya from Ukraine compiled some very interesting research on the negative health effects of this kind of flicker.

Fluorescent lights are available in a wide range of colour temperature. Cool should be avoided, particularly for evening use since the blue light interferes with sleep and may have other negative effects. FLs also "leak" ultraviolet light, which can also interfere with sleep, and damages tissue/material. The UV light emitted is not the beneficial kind (UVB), except for specialized lamps, i.e. those used for pet reptile enclosures.

The emitted colours are limited to a few sharp peaks in the spectrum, so colour quality is poor, and some materials can appear as a noticeably different hue under fluorescent vs natural light. These lights do not emit infrared light except for specialized models.

Fluorescent lights are not recommended for eyestrain and/or myopia sufferers due to the inherent flicker, although they may be preferable to flickering LED due to the "softer" nature of fluorescent flicker as discussed in the article on flicker.

Light Emitting Diode

LEDs work by passing electricity through a light-emitting semiconductor material. There are often multiple LEDs fixed to one bulb unit. These LEDs are often used in conjunction with diffusing layers, phosphor coatings, or other materials to maximize efficiency, colour rendition and light uniformity.

LED technology does not flicker inherently, but manufacturers of LED devices tend to make them flicker by design to reduce energy consumption, and maximize LED life by reducing heat. Also, dimming by reducing the voltage passing through the LED can lead to colour shifts, so manufacturers tend to dim by using pulse-width modulation, a form of flicker.

LED bulbs are also available in a wide range of colour temperatures. Cool colour temperatures should be avoided for evening use due to blue light

The spectrum of light emitted by common LED bulbs tends to have the strongest peak in the blue part of the spectrum, since blue-emitting semiconductor material is used to drive the yellow-orange phosphor material, which combines with the blue to appear as white light. Colour rendition is inferior to daylight or even incandescent. There do exist "full spectrum" LED lamps for colour critical environments, for growing plants, or for phototherapy. I do not have experience with these, but if they do not flicker they are likely a good alternative to standard LED lamps.

LEDs do not emit infrared or ultraviolet light unless specifically designed to do so. I recall reading a study about mice raised under LED lights, which had thinner retinal photoreceptor layers than the control group of mice. Likely because they were lacking the infra-red light, which apparently triggers retinal cell regeneration.

My experience with LED room lighting is limited. I bought a set of LED bulbs (Sylvania 79288) to replace the power-hungry halogens in a kitchen track light. The bright bulbs revealed some grime in the kitchen, so I spent the next half-hour cleaning - a strong headache ensued. I suspected the lights, and verified flicker with the camera.

I've used another set of LED bulbs for the bathroom (GE Bright Stik 65186) without any eyestrain/headache symptoms.

Electron Stimulated Luminescence

Electron Stimulated Luminescence (ESL) light bulbs are a unique lighting technology brought to market by VU1 corporation. The bulbs are essentially compact cathode ray tubes where electrons are blasted onto a white phosphor coating to emit light. Unlike the CRTs used for televisions, these do not seem to flicker at all, aside from minimal brightness modulation due to the supplied AC - less than incandescent bulbs, due to the long phosphor decay.

Advantages of this bulb type are improved light quality (compared to LED and Fluorescent), flicker-free operation, more energy efficient than incandescent, and they are free of mercury.

The main disadvantage is the bulk / weight of the bulb, which makes it impractical for some fixtures, and unfortunately as of early 2019 the bulbs are increasingly rare.

External links:

incandescent slow motion
https://www.youtube.com/watch?v=eUprJS9sXYU

test of different room light sources for UltraViolet
https://www.youtube.com/watch?v=21TJYkhP8gQ

LCD

Liquid Crystal Display is the most common display technology of the present, and has held this place for almost two decades.

Most LCD displays have 2 components, the LCD panel itself, and the backlight. Earlier displays have CCFL (cold-cathode fluorescent) backlights, while more recent models have LED (light-emitting diode) backlights.

LCD televisions and monitors are commonly called "LED", but this is erroneous. Marketers at dishonest companies like Samsung began calling their LCDs with LED backlights this way to make them seem like more of a technological advancement than they actually were. Consumers fell for this "re-branding" and were also attracted to the higher showroom brightness. (Samsung has tried this again with their "QLED" branding. This is just another iteration of LCD, with improved colour gamut due to incorporation of Quantum Dot materials.)

A few types of LCD work without backlights - those found in calculators or digital watches, for instance - but those are outside the scope of our interest here.

The LCD panel itself uses liquid crystal cells along with polarization to block or transmit light for each pixel. This is known as transmissive display technology, as opposed to technology like OLED which is emissive, where each pixel emits its own light. LCD panels for PC monitors tend to have the polarization layers configured such that when no power is applied, the pixels are white, while Televisions tend to be configured such that when no power is applied the pixels are black Despite decades of research and development, the liquid crystal cells are still not able to block light completely. This is why an LCD showing black in a dark room still emits light.

As of early 2019, a new type of LCD is emerging in the professional displays market, called Dual Layer LCD. This technology actually has 2 separate LCD matrices, which are sandwiched together to block light extremely effectively. These displays consume much more power due to the brighter backlight required, and are quite expensive. It is yet to be seen if such displays will make it into the mass consumer market.

In the quest for improved panel characteristics, manufacturers have come up with many different LCD panel types. If you have shopped for an LCD recently you will recall terms like "TN", "VA", "IPS". These designations refer to the liquid crystal configuration used in the subpixels. The main observable differences between the panel types are viewing angles and pixel response. However, TN (Twisted Nematic) panel types are best avoided by those who are sensitive to eyestrain, since these are 6-bit panels rather than 8-bit, and to achieve colour quantity similar to true 8-bit they actually flicker subpixels rapidly, a technique called Temporal Dithering. If dithering is linked to frame rate it is called frame-rate controlled (FRC). Other monitor types are not necessarily free of temporal dithering, so it is best to do research/testing before buying. The different subpixel configurations can also vary in how much of a screen-door effect they exhibit, so sensitive individuals should be mindful of this characteristic.

In order to prevent the sub-pixels from getting stuck in the active position, LCDs are designed to invert the voltage of the pixels with each refresh cycle in a process called Inversion. This creates a subtle flicker on the pixel level since the inverted voltage does not match the previous voltage perfectly. Typically the pixels alternate positive and negative voltages in a checkerboard pattern, which masks the inversion flicker on normal content. Displaying a specific checkerboard pixel pattern will un-mask the flicker. See external links below for inversion tests. For PC monitors inversion is most visible on dark content with the backlight very bright, and viewed from an extremely close distance, appearing like a very subtle static - the static can appear colourful if the RGB subpixels are not inverted as a full pixel. Lower power LCDs as found in phones, tablets and laptops tend to use Row Inversion which masks the flicker less effectively.

If the pixel-level flicker is bothersome to you, seek out an LCD with the subtlest inversion pattern possible. Also, inversion/dithering techniques can vary with the graphics driver, monitor driver, or Operating System used, so it may be worth trying a different OS or driver version. Displaying brighter content should minimize visible flicker. It may help to slightly blur the image by adding a diffusing layer on top of the screen. It may also help to wear reading glasses to keep the image slightly blurred. If all else fails, it may be best to avoid LCD and try working with an E-ink device. Unfortunately these are rather limited in what they are able to display as of 2019.

I have not experienced negative reactions to pixel-level flicker, aside from when trying out inversion pattern tests. Two different LG panels I've tried had a strange artifact where while moving my eyes quickly a "grid" would appear. It seemed like this began straining my eyes, but I did not use them long enough to find out how bad it would get.

Due to the hard edges of text displayed on an LCD, software-based subpixel rendering technologies were implemented, best known by the brand name ClearType. This technology likely exacerbates reactions for those sensitive to dithering and inversion.

LCD panels by default keep the frame on screen between refresh cycles. This is known as "sample-and-hold" refresh, which is good for eyestrain sufferers since it does not inherently flicker. More about this in the article on refresh.

Due to the way humans perceive motion, sample-and-hold displays have poor motion clarity. Using this type of display for full-motion video and gaming is detrimental to vision since the eye can not actively focus on the blurred motion

There are several techniques used to improve motion clarity on LCDs. These are detailed in the article on motion enhancement.

The backlights themselves and not the panels are the cause of flicker and therefore eyestrain in the majority of cases. Many newer LCD monitors are being marketed as "flicker-free" - getting one of these will be good enough for many sufferers of eyestrain. Many of the older monitors do not flicker while the backlight is set to 100% (see the page on flicker for methods of detection). Full brightness will probably not be comfortable to use, especially in darker rooms, so unless you are OK with wearing sunglasses at your screen, I suggest buying a small roll of automotive window tint and taping some rectangles of it in front to dim the picture "flicker-free" (amber tint will block more of the harmful blue light).

The flicker of CCFLs tends to be less irritating than LED flicker. This is because the electrified gas in the CCFL tube tends to glow a little after the current ceases, whereas LEDs are instant-on, instant-off. Unfortunately, the LED backlights tend to be designed for even lower frequencies than the CCFL.

The backlights are designed to flicker because it is a more electrically efficient method of dimming. This is called PWM dimming, (pulse-width modulation). The method found in "flicker free" monitors is known as voltage dimming. Some monitors are marketed as "PWM-free", but this does not necessarily mean that they are flicker free, it just means that they don't use PWM to dim the screen.

Many LCD televisions have the ability to dim specific zones of the screen to improve contrast. This technique is called local dimming. This is also called Full Array Local Dimming (FALD) when there is a complete grid of addressable LED zones. Unfortunately, this dimming is typically done with PWM, so a bright scene can look perfectly fine, while a dark scene can cause horrible eyestrain - if you are sensitive to this it's best to turn local dimming off.

Pages with info on inversion and test patterns:
http://www.techmind.org/lcd/index.html#inversion
http://www.lagom.nl/lcd-test/inversion.php

Informative article on the evolution of LCD backlight technology:
https://pcmonitors.info/articles/the-evolution-of-led-backlights/

OLED

Organic Light Emitting Diode is an emissive type display technology, meaning that the pixels themselves emit light, unlike LCD, which is transmissive meaning that the pixels block light.

OLED is among the newer of the display technologies, and is gaining ground against LCD in the displays market. As of early 2019 it holds a large share of high-end mobile devices, VR devices, and most of the top-tier televisions. Within a decade it will likely be the main method of displaying digital information. Competing emissive technology such as microLED may arise, but from our perspective, there should not be much difference between mLED and OLED.

As an emissive display the inactive pixels remain perfectly black, giving displays a stunning contrast ratio which LCD cannot even approach. There is also great potential for power saving, as long as the display is showing dark fields with light text. Another advantage is the simplicity of construction, which does away with LCD's many layers. The main disadvantage of OLED (and other emissive display technologies) is that they are susceptible to "burn-in", where pixels which are used more get dimmer. Static content (i.e. taskbars, game UIs, channel logos) displayed for long durations will leave a permanent after-image

OLED is capable in being refreshed in many different ways. Sample-and-hold drive seems to be the most common, but some have a rolling refresh. Once the panels get bright enough, it's even possible that they will be able to emulate CRT displays, illuminating only one line of pixels at a time.

My experience with OLED began in the spring of 2011, with the SanDisk Sansa Clip+ MP3 player. The display is tiny and monochrome, the bulk of the pixels are cyan with a strip of yellow towards the top. The display has a rolling refresh, which would probably be irritating had I used it for prolonged periods.

Next was a viewfinder in my camera, the Panasonic FZ1000. I have never had any eyestrain experience with this display, although again, the viewfinder is not being used nearly as long as a monitor or TV.

Having used a large format CCFL LCD for a few years and experiencing eyestrain issues and no noticeable improvement in my vision, I decided to purchase an OLED TV to use as my main display.

In the autumn of 2014 I bought a 55EA9700 which was the first-gen OLED LG offered in Canada. I had tested it for a few days. Eyestrain did not seem any worse than with my LCD, no obvious flicker. The panel developed a "line artifact", so this, along with a few other issues (unrelated to eyestrain) convinced me to return it rather than exchange. Unfortunately it is not conclusive to me how my eyes would react in the long term with this first gen OLED panel.

Autumn 2018, again decided to give OLED a shot, this time with Panasonic's TC-55EZ950.

First full night with the display, I settled in to watch a film. Within a half hour, symptoms developed - first, unwillingness of the eye to focus, then a familiar dull pain in the eyes, followed by headache. Photos taken at very high shutter speeds (1/5000th - 1/16000th) revealed black lines, indicating a flicker calculated to be somewhere between 120 and 144 Hz. Tested the TV at all brightness settings and options. Nothing removed the flicker. I even contacted Panasonic, who eventually replied that no flicker should be visible. While at the store to return the TV, I took photos of every OLED: LG, Sony, the other Panasonic model - all exhibited the same flicker. RTINGS reviews of OLED televisions confirm the presence of this flicker.

To reiterate: All 2018 OLED TVs would induce eyestrain for myself, and anyone with similar sensitivity due to a high frequency flicker which can not be disabled. This is unlikely to change in the future, since panel manufacturers are always trying to maximize apparent brightness while minimizing power consumption. The obvious solution would be to introduce an optional "flicker free" mode, which eliminates flicker at the cost of limiting brightness.

Rtings reviews of OLED televisions, see the section in each review entitled "flicker-free"
https://www.rtings.com/tv/reviews/best/by-type/oled

E-Ink

The technology found in many E-Readers is referred to as electronic paper, electronic ink, or "E-Ink", and falls in the general category of Reflectve displays (as opposed to Emissive or Transmissive display).

Although there is some variation in how the technology works, the common devices work by submersing an electronic pixel grid in a fluid of "ink" particles which are electrically charged. Black and white particles are oppositely charged. As the device changes voltages of the pixels, the particles re-orient themselves to suit the applied charge, thus forming the text/image. Devices with coloured "inks" are starting to appear on the market.

These devices refresh the image only on demand, i.e. when changing pages, so the image is retained without power being applied.

This technology do not emit light itself, relying on an external light source. Use daylight/sunlight whenever possible, and select a bright, eye-friendly lamp type as discussed in the article on room lighting for evening use.

From an eyestrain perspective, there should not be much difference between using one of these devices and viewing actual printed media. If experiencing eyestrain it will likely be caused by the lighting technology itself, or the environment setup.

The devices are not yet full colour or fast enough for real-time motion, but once these goals are met these devices when used with natural lighting have the potential to be the most eye-friendly displays available.

ClearInk corporation is developing reflective full-colour high speed reflective displays.
https://www.clearinkdisplays.com/technology

CRT

Cathode Ray Tube enjoyed over a half-century of popularity as the main home and office display type. CRT TV and monitor production ended in the 2000's as LCD displays were introduced. Consumers embraced the obvious advantages of LCD: thin screens, light weight units, higher resolution, but CRT actually has several advantages over LCD and other display types.

CRT has the highest motion clarity of any display technology (other than true laser projection) due to having the lowest persistence refresh. The technology works by scanning a beam of electrons across the phosphor coated glass screen, scanning by horizontal line (called "scan lines"), from top to bottom. The electron beam and excited phosphor provides enough brightness such that it can even act as the light source in CRT projection.

Since light is emitted only where required, CRTs can display perfect black levels, however the bright room black levels suffer since the phosphor coating is typically a dark grey which gets illuminated from the room side.

CRTs do not emit infra-red or significant levels of blue or ultraviolet light.

Due to the imprecision of the electron beam, CRTs do not have as sharp pixels, or screen door effect like LCDs do.

Although CRT displays flicker, the flicker is less irritating than an LED flicker operating at the same frequency, since it has a smooth fall-off/ decay in brightness, whereas LEDs are instant-on, instant-off. 60 Hz CRTs were tolerable for most people, while a 60Hz LED flicker would be unbearable for most.

With respect to myopia, the 60Hz CRT monitor probably contributed to the loss of visual acuity among many users. Since the image is actually much darker than it appears to be, the pupil opens wider than it would for a non-flickering image of equal apparent brightness, forcing the eye muscles to work harder to bring the close image into focus, triggering elongation of the eyeball - the same principle as why doing close work in a dark room is harmful.

I had used CRT monitors/televisions up until 2006-2007. I did experience slight flicker induced eyestrain with 60Hz monitors and bumped the refresh rate up to 75Hz whenever possible.

Although CRT has been largely phased out, its characteristics will prevail. Once OLED or mLED displays gain high enough pixel brightness, it is likely that they will be driven the same way that CRTs were, to gain improved motion clarity.

Slo-Mo Guys show how CRT TVs work:
https://www.youtube.com/watch?v=3BJU2drrtCM

Plasma

Plasma displays, also referred to as PDP, (plasma display panel) is a technology used mainly for televisions, introduced in the 1990's and peaking in popularity in the late 2000's. Plasma and LCD competed in the high-end TV market for years, with Plasma gradually losing popularity due to their lesser brightness, and their inability to scale to UHD / "4K" resolution. Other practical considerations sealed Plasma's fate: their high energy consumption, their heavy weight, relative fragility, and susceptibility to burn-in.

Plasma is an emissive technology, meaning that the pixels themselves emit light. Each subpixel is a cell filled with a gas, which, much like a fluorescent tube gets excited into a plasma "arc" state with the application of high voltage. The cells have a phosphor coating corresponding to the subpixel colours, red green and blue.

As an emissive technology Plasma is able to deliver much deeper blacks than LCD, since the plasma cells showing black are simply not discharging - there is a slight glow since the cells are kept ready with a "background" charge, but typically it's much darker than the light leakage of an LCD panel. The black levels suffer in a lit room, since the dark grey phosphor coatings are illuminated from the room side.

The screens themselves are made of glass, and so are glossy / reflective.

Plasmas are excellent for reproducing motion since they have a pulse refresh., where frames do not persist for long. Some people can see yellowish trails when moving the eyes quickly across these screens, this is because the decay time of the different colour phosphors are not perfectly equal, with blue's glow fading first, green and red persisting for longer. I have observed such trails on a late gen Pioneer Kuro. Most people can detect the flicker of the pulse refresh, particularly if showing a white scene, and especially noticeable if it's in the peripheral vision.

When looking at a solid colour field up close, one can observe subtle noise in the picture. This is due to slight variations in discharge brightness. It varies very quickly since the cells are illuminated typically 60 times per second.

International regulations limit the amount of power that televisions can consume, so Plasmas are restrained by a feature called ABL: automatic brightness limiter, where the overall brightness of the picture is dimmed when the average brightness of the content reaches a certain point. This is easy to demonstrate if a PC is hooked up to the Plasma - take a white window and stretch it to different sizes. The white will dim as the window is enlarged and brighten as it shrinks. OLED televisions also have this feature, but it only manifests itself when the TV is set up at an extreme luminance level.

Due to the inherent flicker of the pulse refresh, Plasma is not well suited to long-term use for those with eye strain issues. For content which is mostly still, i.e. photo viewing, certain games, desktop work, LCD is a better choice. If you find yourself using a Plasma for desktop work it is probably best to change the UI theme to light text on dark backgrounds since this will make the flicker much less prominent (and save a lot of energy) . On the other hand, Plasma excels at representing motion, so if used for fast-action gaming, sports, or movies, it may be the better choice if your eyes are able to focus on the flickering image. LCD televisions can only compete with Plasma's motion if they have motion enhancements enabled, but these come with their own drawbacks.

Plasma likely "leaks" ultraviolet, similar to how fluorescent lighting does. Blue light output is less significant than with a typical LED backlit LCD, and can be further reduced by selecting a "warm" picture preset. Infra-red output, aside from the longest wave (heat) is likely minimal.

Video of a plasma display in slow-motion:
https://www.youtube.com/watch?v=FMlpl7AmvNo

Projection

Projection has over a century of history as a display technology, and through continuous innovation still has the ability to provide some of the most compelling visual experiences available. The main advantage of projection today is the sheer size of the image, which other technologies cannot match without extreme cost. The main disadvantage is the need for darkness to produce a picture with reasonable contrast ratio - projectors cannot subtract light, therefore, the darkest part of the image will be limited to the brightness of the projection surface + ambient light. Many of us will recall straining to read a projected image in a classroom or office that was not light-controlled.

Front projection is when the projector shines towards the viewer's front - the typical setup in cinemas. Rear projection is when the projector shines towards the viewer's rear, with a translucent projection screen between the projector and viewer.

Rear Projection Televisions (RPTV) are simply a rear-projection setup contained within a television unit. They make clever use of lenses and mirrors to shorten the light path, as well as using special materials in the screen to make the projection look good even in a room with ambient lighting. The technology used in RPTV does not differ from front projection otherwise.

Emissive Projection

The following technologies can be called emissive projection. Of course, all projectors emit light, the distinction is that the light source and image source of these technologies are one and the same.

CRT Projection - these use a separate Cathode Ray Tube to emit light for each colour channel; red, green, blue. Since the image has a scanning refresh, motion is reproduced with high clarity, and since the black parts of the image are not illuminated, contrast is excellent in a light-controlled room. These projectors and their RPTV counterparts tend to be quite massive and heavy, which led to their decline in popularity. From an eye strain perspective, expect similar issues from CRT projection as with a regular CRT television or monitor - perhaps worse since it is used in a dark room.

Laser Projection - not to be confused with DLP or other technologies using laser light sources - true laser projection is similar in operation to CRT. One line of the image is scanned at a time using a micromirror which directs the light across the field while the lasers of different colours are modulated. Blacks are truly black since the lasers are simply turned off, so it is capable of rendering excellent contrast. As a scanning refresh display, motion is quite clear, even at 60hz refresh. I have tested the Sony MP-CL1, and did not find it particularly straining to look at, I'm guessing because the lasers have some decay time as they shut off. However, my eyes could not focus on the inherently flickering image - similar to my reaction with fluorescent light - not especially eyestrain inducing, but my eyes simply cannot focus.

Non-Emissive Projection

The technologies below all rely on a separate light source, rather than the technology itself emitting the light. Many of these projector types use the UHP "ultra-high pressure" lamp. These lamps are run at alternating current, causing a flicker ranging from 90-500 Hz. I have tested an older Sony LCD projector, the VPL-PX1 and found the UHP lamp flicker to be particularly fatiguing - eyestrain / headache within 15 minutes.

Newer projectors use LEDs rather than bulbs. This has the potential to be flicker-free, but comes with the drawbacks of LED lighting (incomplete colour spectrum, abundance of blue light, and lack of infra-red). Some newer projectors, particularly the smaller "pico" devices use rapidly sequenced red-green-blue LEDs as the light and colour source - I do not recommend those if you are prone to eyestrain.

Some higher-end projectors use a laser light source, where a laser stimulates phosphor material to produce light/colour. My understanding is that this saves energy and improves colour rendition. I have not tried such a device personally, but if the laser operates without flicker it should be a more eye-friendly light source than the UHP lamp.

Some rarer / older projectors use halogen bulbs. Assuming that it is illuminating a flicker-free technology, this is potentially the most eye-friendly form of projection one can use. It has the added benefit of infra-red light. For the technically inclined, it may be possible to retrofit UHP or LED projectors with Halogen lamps.

DLP Projection - A technology by Texas Instruments, known as Digital Light Processing, these devices use a tiny chip covered by a grid of micromirrors. Each micromirror represents a pixel. Light is shone onto the chip, which the micromirrors then either reflect into the projection path/lens, or away from it. Since the mirrors can only function in a binary way, for shades of brightness the mirrors rapidly oscillate between states.

With single chip systems colour is introduced by means of a colour wheel, which spins through the light path and is synchronized with the mirror oscillation to turn colours "on" where required. An artifact of this technique is the "Rainbow effect" where, when moving the eyes rapidly, some people can see rainbow trails on objects on-screen. Some LED projectors use rapidly changing red green and blue LEDs synced with the mirror oscillations to introduce colour.

3 chip systems have one chip for each colour channel. This eliminates the rainbow effect, but drives up the cost of the projector substantially. 3-chip DLP are the type of projector typically found in commercial cinemas.

Since DLP type systems are all based on flicker, they are likely to induce eyestrain, particularly when viewing darker content. I have not had a chance to test such displays myself for significant time, but I can confirm that I see the rainbow effect, and it is bothersome, at least aesthetically.

LCD Projection - this method shines light through a Liquid Crystal Display panel (or three panels, one for each colour channel) which is then focused with a lens onto the projection surface. Contrast tends to be worse than with DLP projection. Content aside, eyestrain from LCD projection is most likely caused by the light source, i.e. the projection bulb, since the LCD panels do not flicker inherently, except perhaps with pixel inversion. Another factor which could induce eye strain is the "screen door effect".

LCOS Projection - LCOS uses a liquid crystal "shutter" for each pixel over a still mirror chip's surface to block or reflect light into the projection path. Sony's version is called SXRD. The projectors typically use one chip for each colour channel, while the smaller "pico" devices will use a single chip synchronized to a rapidly changing RGB LED light source - with camera viewfinders and similar applications this is known as a "Field Sequential Display". To my knowledge, LCOS chips do not inherently flicker. LCOS tends to have a poorer contrast ratio than LCD, but better colour rendition.. LCOS is known for having softer pixels, or less of a "screen door effect". So for those who get eyestrain from a visible pixel "grid", this technology may be a better choice.

Projector Central offers a wealth of information about projectors:
https://www.projectorcentral.com/

Incandescent LCD, Daylight LCD

Since the backlight of an LCD monitor is often the source of eyestrain symptoms, whether due to flicker, abundance of blue/ultraviolet light, or a combination of these factors, it makes sense to consider if the backlighting could be changed to a more eye-friendly type.

As discussed in the article on room lighting, incandescent light is the most natural and therefore most eye-friendly of the artificial light sources. Of course, nothing can beat sunlight/daylight for daytime illumination. This article will discuss my experiences with adapting monitors to use these light sources.

WARNING: This article describes taking apart computer monitors, devices containing sources of high voltage which can cause electric shock leading to injury or death. Do not attempt taking apart a monitor without researching and implementing the safety measures required to work on electronics.

Attempts to disassemble monitors will void any warranty on the product. Monitor internals are fragile and must be handled with care. Cold cathode fluorescent tubes found in some monitors contain toxic mercury, which can contaminate the environment if the glass tube is broken.

Incandescent light sources produce significant heat and can start fires if not kept away from combustible materials.

Any attempt to disassemble and/or modify a device is at your own risk. This author cannot be held responsible for any damaged / disabled equipment, or personal injury.

Incandescent LCD

At the very start of 2019 I was experiencing worse eyestrain symptoms than usual with my main display, a large format LCD monitor. I decided to try taking apart a spare monitor which was laying unused at home, with the goal of converting it to incandescent backlighting.

The web page of Vasya from Ukraine on displays and eyestrain was in large part my inspiration for this - he had set up his own incandescent LCD monitor to relieve his symptoms.

I actually had tried this a few years back with an older monitor (NEC Multisync 1700v), but was unsuccessful since the ribbon cable configuration of that particular model did not allow separation of the LCD panel and backlight layers during operation.

With this newer monitor, an LG Flatron L1970HR, I was able to take apart the monitor with relative ease after watching a few repair videos online of similar models. From there it was pretty straightforward to separate the LCD/backlight layers and prop them up in an "A-frame" such that a desk lamp could be shone in between the reflector and diffuser layers.

The CCFL backlight lamps could simply be unplugged since this monitor will display a signal without them.

This particular monitor is originally edge-lit, so placing a desk lamp with a 40W incandescent bulb at the side as in the photos works well to diffuse the light equally across the screen. At the opposite end from the lamp is a "reflector" made of a white sheet of paper with an aluminum foil backing - light "leakage" must be minimized to get even illumination, but some distance and openness must be maintained to prevent overheating the electronics and risk of fire.

(The camera's white balance is set to daylight, so the displayed image looks quite orange. This it is not noticeable when using the monitor in the evenings since our visual system adapts to different colour temperatures with ease. Also, the vignetting is less visible in person.)

Switching the lamp on, I was greeted with a very warm and pleasant picture. Quite relaxing to look at. Colour quality is actually improved since incandescent emits the full spectrum. A few evenings of use and no eyestrain whatsoever. Further, within a couple of months using this monitor only in the evenings/weekends I noticed significantly sharper vision - this was totally unexpected!

From this experience with incandescent LCD, a few important "puzzle pieces" fell into place with my understanding of eyestrain and myopia. First that flicker, even the very fast flicker of a CCFL at 100% brightness, was not only a source of eyestrain but also prevented vision improvement.

Second, I understood that the absence of infra-red light in standard monitors was a problem, not just the abundance of blue/ultraviolet, since in the past I had tried a "flicker free" LCD monitor with LED backlight (Benq EW2740L) without noticeable eyestrain relief or improvement of vision.

Daylight LCD

Sunlight/Daylight is obviously the ideal light source for backlighting a LCD in the daytime. Incandescent light appears quite orange in a room with daylight, and to get a comfortable brightness in a day lit room, considerably more than 40W of power would be needed.

After taking off the back panel, along with the inverter board, (which, surprisingly, this monitor does not need to have connected to display a signal) I was able to lean the LCD panel against my window and use it.

With an unobstructed south facing window on a sunny day, light quantity is adequate for most of the day. Direct sunlight shining at the back of the panel creates a beautiful picture with eye-popping colour quality that no conventional monitor can match.

Unfortunately on heavy overcast/rainy days the light quantity passing through the LCD is not adequate for comfortable use, so some supplemental lighting is needed. Light transmission of LCD panels is about 10% at best.

To use a daylight LCD at a window comfortably, you must be positioned high enough above the monitor such that you are looking downward towards the monitor and ground outside. Otherwise if the sky is in your field of view, it will make the LCD appear uncomfortably dim. As a work-around one could shade out all of the window except where the LCD is located. Anyways, there are endless possible configurations depending on the space you have to work with.

I suppose that such a modification to a tablet or even a phone would be possible, but I do not have experience with such devices, and it is my understanding that many of these are very service un-friendly, requiring specialized tools to open up.

Another Incandescent LCD Build

In August of 2019 I completed another incandescent LCD build. The goals of this build were to make the light source completely flicker free, upgrade the resolution, and to better integrate everything into a single "package".

I happened upon a Dell P2412H for a very low price. In its original state the monitor was quite offensive to my eyes, with harsh purplish LEDs and aggressive PWM dimming - it was disassembled shortly after testing.

To make the backlight completely flicker free I got a DC power supply (12 volt 9.5 amp), which powers six 12v 11w "wedge base" type bulbs (used commonly in landscaping and automotive applications.) Just like with the original LEDs, the lights shine from the bottom of the panel, the internal layers work well to diffuse/reflect the light evenly.

The frame is made of standard metal framing channels. 22mm or 7/8" hat channels for the sides and "legs", and 92mm or 3 5/8" tracks for the base. Lights are mounted in a removable tray which sits at the bottom of the tracks. The track depth of 92mm was selected to put distance between the light source and panel, to keep the panel from getting overheated by the lamps and also to minimize visual "hotspots".

Tips For Monitor Modding

Safety first, of course. If you are not comfortable with electronics, it may be best to find someone who is. Maybe even a local computer repair shop can help you.

If inexperienced, don't start with modding your main display or laptop. Start with a cheap/free/recycle-bin find to become familiar with the disassembly procedures and inner composition of these devices.

Watch repair videos online for taking apart your, or a similar monitor.

take photos, notes, and make small marks on parts to make sure that they don't get rotated/reversed.

I have found that CCFL monitor panels tend to have better light transmission than LED panels. More white, less of a green colour cast.

CCFL monitors tend to be more robustly built than LED ones, but they also contain higher voltage parts, and fragile CCFL tubes.

Be very careful not to scratch any of the inner layers of the monitor since such a scratch will be highly visible on the picture once illuminated.

Avoid prying apart layers unnecessarily since any dust or lint specs introduced between layers will be very visible once illuminated

Parchment paper makes a decent and very cheap diffuser if you need to soften the light, another benefit is that it's highly heat resistant.

Be conscious of temperatures, and keep all flammable materials away from the incandescent lamp. Also note that incandescent bulbs get hotter over time as their filament thins.

Be very careful with halogen bulbs since they run extra hot compared to standard incandescent by virtue of the filament being very close to the envelope. They are also highly pressurized and can explode if mistreated. Any surface damage can cause them to explode: bulbs handled with bare hands are damaged once heated since the skin oils create a weak spot in the envelope.

Flicker

Flicker is the most common cause of eye strain, headaches, and other symptoms associated with display devices. Often the flicker is too fast to be visible with the un-aided eye, but it can still have negative impact on the eyes and nervous system. Sources of flicker must be identified and eliminated from the environment for relief of eyestrain symptoms.

It is important to check not only your display device, but also all the light sources in your environment. It's entirely possible that your desk lamp, or LEDs on your mouse/keyboard are flickering and contributing to eyestrain.

More obvious (lower frequency) flickers can be detected by quickly moving the eyes across a bright image, or waving the mobile device while keeping your gaze static. If a series of rectangles appear rather than a smooth trail, flicker is present.

Flicker is more perceptible in the peripheral vision than in the central vision, so viewing the light source through at the fringes of your field of view can help identify flicker.

Detecting higher frequency flickers is trickier. Using another device like a digital camera or mobile phone is helpful. Flicker can show up in the electronic viewfinder or phone's screen due to interference with the device's sampling frame rate and the flicker frequency. Many newer devices have complex processing methods which can cancel out the flicker, so it's not a reliable method of checking, unless you are certain that your particular recording device is not doing that kind of background processing.

The most reliable method I've found is to use a digital camera which has a manual mode. Turn the ISO all the way up, exposure time to a very short time (1/4000th of a second will be adequate for detecting most flickers), set aperture as wide as possible if more light is needed. With motionless content on screen, ideally white, take a series of stills with these settings - any variation of brightness, banding, or other line artifacts are a sure indicator of flicker.

Most newer cameras use CMOS sensors which capture the image line by line, introducing distortion called "rolling shutter effect". This effect complicates trying to calculate the flicker frequency from a photo since the sensor update speed/direction must be taken into account.

Another method is using a small fan - computer case fans work well due to the black blades. Spin the fan quickly while looking through the blades at the screen. The blur of the blades should be perfectly smooth, as it looks if you spin the fan while looking at daylight out the window. If you see dark "fin" patterns it indicates the presence of flicker.

Several factors determine how irritating a flicker is:

The lower the flicker frequency is, the more irritating it is.(to a point, once you get down to say 1 cycle per minute, it starts getting less irritating as it slows.)

The greater the contrast of the flicker, the more irritating it is. This factor might explain why a device which you can use without issue in the daytime under ambient lighting conditions causes eyestrain in a darker room at night.

The less gradual the flicker is, the more irritating it is, i.e. a light source that switches on and off instantly like LED is more irritating than Fluorescent, which tends to glow for a short time after emission. Picture a square wave vs a sine wave. For example, CRT monitors flickering at 60Hz were tolerable to the vast majority of people since the phosphor has an afterglow which gradually fades, whereas a monitor with LED backlight flickering at 60Hz would be completely unusable for most.

The larger the percentage of the field of view that is occupied with flicker, the more irritating it is. The whole room being illuminating by a flickering light will be more irritating than only a small hand-held device flickering.

Users may not experience negative reactions to flicker at first, but the reaction can gradually worsen with repeated/prolonged exposures in a process called sensitization.

Some people report blurrier vision under flickering lights. In my case, the first year or two of myopia symptoms only manifested under fluorescent lights. This is because the pupil is opening wider than if under constant light, since it is actually dark in the room for the "off" phase of the flicker - it only appears bright because of a human factor called "persistence of vision" which is covered in the article on motion perception.

The wider pupil lets in a wider angle of light rays than a smaller pupil which lets in a narrower angle. This is the same reason why myopics can have significantly worse vision in darker environments.

Doing close work under flickering lights is particularly harmful since the lens must refract more than it would with a smaller pupil.. More on this in the article on close work and myopia.

As covered in the article on vision habits active focus is critical to maintaining one's eyesight, but I've found that my eyes have great difficulty maintaining active focus on a flickering image/light source. This is part of the reason why my vision improved so rapidly once I had set up my Incandescent LCD, my eyes began to naturally actively focus on the screen.

Refresh

The process by which a display changes the image being displayed is called refresh, sometimes also referred to as drive. The frame rate of the content being displayed is not necessarily the same as the refresh rate, i.e. a television with a refresh of 60 times per second (Hz) can display 30 frame per second (FPS) content. It will simply show each frame for two refreshes. A 60 Hz display could also display 120 FPS content, but every second frame of the content would be skipped.

With the exception of e-ink technology which refreshes only on demand, the refresh process happens constantly, regardless of what is being displayed. Even if things appear perfectly motionless, the display is still refreshing at its designed rate.

The most common refresh rate with modern devices is 60Hz. High-end gaming monitors are up to 240 Hz as of 2019. Television content is typically 30 FPS, increasingly 60 FPS for sports and other fast action content. New on the market is High Frame Rate, or HFR content, which offers 120+ Hz content, but it has not seen widespread adoption. Feature films are still typically 24 FPS, and are filmed with longer frame exposures, which makes the choppiness of motion less apparent - this creates the distinctive "cinematic look".

Refresh Methods

To understand why the different methods of refresh vary greatly in their ability to reproduce motion, see the article on Motion Perception.

Sample and hold - This is the most common drive method currently, due to the proliferation of LCD displays. It displays the entire image for the duration of the refresh cycle, at which point the next image wipes over the previous. This is the most eye-friendly method (at least with mostly static content) since it does not inherently flicker.

The methods below all inherently flicker, which can cause eyestrain in sensitive individuals.

Scanning Refresh - This method displays the image one line at a time on a black field, typically scanning from top to bottom of the screen during the refresh cycle. Only one line is shown at a time - the complete image does not exist on-screen at any instant. This method relies on the human visual system's persistence of vision. This drive method is most common with CRT displays, but is also used by true laser projections. Assuming equal refresh rates for comparison, this method of refresh produces the highest level of perceived motion clarity.

Pulse Drive - This method will pulse the entire screen with the complete image for a short duration of the refresh cycle, also relying on human persistence of vision for viewers to perceive the image. This is the method used by Plasma displays. Higher-end televisions have a motion enhancement feature called Black Frame Insertion (BFI) which simulates this kind of refresh. Also, some of the higher-end LCD gaming monitors have a feature called strobing or LightBoost, which pulses the backlight in synchronization with the refresh.

Rolling Refresh - This method displays a band of the image which "rolls" or slides from top to bottom of a black field for the duration of the refresh. It is similar to scanning refresh, but perceived motion is not as clear since more of the frame exists at any one instant. The reason this method is used rather than scanning refresh is because extreme brightness is needed for the single scanning line, which technologies like LCD and OLED are not yet capable of.

Motion Enhancement

Many modern displays have methods of improving how motion is perceived. All of these methods share in common that they reduce the time that a frame is present, since this is the main contributing factor to perceived motion blur. These motion enhancement features are typically optional, and are found in the settings menus of the device.

- Black frame insertion (BFI): This method commonly works by doubling the frame rate of the content, and making every second frame black. With lower fps content, i.e. cinematic film at 24fps, it can quadruple the frame rate, showing each frame twice with a black frame after each instance - this simulates how cinemas displayed films. BFI usually does not introduce input lag, so it is suitable for gaming, or other uses where real-time interaction is needed. Unfortunately, this method of motion enhancement introduces flicker, so it should be avoided by those who have eyestrain symptoms caused by flicker.

- Lightboost: Also known as backlight strobing, is a feature found on high-end gaming LCD monitors. Similar to BFI, except that instead of inserting frames, it simply blacks out the backlight in between the frames. Essentially this is simulating "impulse" type of refresh. Designed for gaming, it does not introduce input lag. Like BFI, this method is based on flicker, so it should be avoided by sensitive individuals.

- Frame Interpolation: This method increases the frame rate of the content by computing and inserting artificial frames using the preceding and following frames as a basis. Since the device's internal computing is making a best guess as to what the artificial frame should look like, errors can be made, particularly with low original FPS content with fast/erratic motion or certain patterns, but in most content errors are not prominent. This method is great for eyestrain sufferers since it does not rely on flicker. It is also good for those with myopia since it allows the viewer to actively focus more on motion. Unfortunately this method can introduce significant input lag, which makes it unsuited to gaming at present. The good news is that as computing power increases, this input lag will decrease. If your device has this option - most commonly found on high-end TVs (name of the feature varies by brand) - it is highly recommended to keep it on for watching television/films.

Lightboost in slow motion:
https://www.youtube.com/watch?v=hD5gjAs1A2s

Screen Door Effect

Screen door effect or SDE, a term usually used in the context of home theater, describes the visibility of the pixel grid (or subpixel grid). It is an analogy to looking outside through a door with an insect screen. The prominence of the empty or black space between the pixels and/or sub pixels is what SDE is referring to.

Strong SDE is associated with eye strain. I am not typically affected by it with LCD monitors, but I performed a test where I overlaid a 2x2 pixel grid pattern over text which I was reading and it induced headache within 15 minutes. If you are slightly myopic, you probably aren't seeing much of the pixel grid, so this aspect of technology seems more likely to affect those with high visual acuity or sharply corrected vision.

An easy fix to this problem is to cover the screen with a thin film of diffusing material - some LCD panels come with a coating which serves this purpose. There exist spray-on solutions, some more permanent than others. Clear Plasti-Dip or similar spray-on rubber product would probably do the trick, and it would be relatively easy to remove from the screen by peeling/rubbing off if desired. Certain proprietary anti-glare/anti-reflective films/sheets will also have the effect of diffusing the visible pixel grid.

Blue & Ultraviolet Light

On the opposite end of the visible spectrum from red and infra-red, we find blue, violet, and ultraviolet light. Photon energy increases towards the blue side of the spectrum, this is why blue and ultraviolet light have the ability to damage tissue and materials.

To understand why our physiology responds in certain ways to certain stimuli, we must remember the conditions that our ancestors evolved to suit. Our bodies expect exposure to blue and ultraviolet light only in the day.

While blue light shines on us, the body does not release Melatonin, the hormone required for sleep. Viewing a display or using room lighting which emits a large proportion of blue light during evenings can cause insomnia and poor sleep quality. Artificial UV light sources can similarly interfere with the circadian rhythm.

As a side note, regular melatonin production/release is critical to general health including cancer prevention.

When the spectrums are analyzed, the most significant component of most "white" LEDs is actually blue. For an easy demonstration, view a black image on a LCD with LED backlight from an off-angle, the blacks will turn bluish/purplish. On better LCDs they will look greyish. Blacks on an Incandescent LCD appear reddish since red is the primary component of incandescent lighting. Blue (along with indigo and violet) light is energetic enough to damage the retinal photoreceptor layers deep in the eye, unlike UV which is impeded by and does more damage to the frontal cornea and lens tissues.

LEDs do not produce UV unless specifically designed to do so while Fluorescent lighting produces damaging UV during normal operation. The white plastic base on CFL bulbs which have been used for a few years often yellow significantly where they are exposed to the brightest light, much like white plastic left in the sun. The Cold Cathode Fluorescent Lamps (CCFL) used for backlights in the older generation of LCD displays similarly emit UV - how much actually passes through the LCD layers will vary due to differences in design and materials used in manufacturing.

Minimize Blue/UV exposure by following these tips:

- Adjust the colour temperature of your display to a "warm" setting. This can be done in the hardware menu, or the software video settings. There are also 3rd party applications which automatically adjust the colour settings based on time of day.

- Wear amber tinted glasses, or use an amber tint over your screen

- Use a display technology with minimal blue light output, like a projector with halogen light source or Incandescent LCD

A note regarding Blue/Indigo/Violet light and myopia: Since becoming nearsighted I have always noticed that blues appear much blurrier than reds For example blue Christmas lights from a distance just look like a blue fog., whereas I could pick out the individual points of red Christmas lights from the same distance. A blue line vs a red line on a black background CAD program, I would have difficulty telling if the blue line has thickness applied or if it were a double line or not. Blue light bends more than red as it refracts through a substance, for this reason in a rainbow blue is found on the inner radius. Another refractive substance is the lens and fluid of the eye, blue light bends more so its focal point is further in front of the retina than for reds, functionally making the degree of myopia stronger for blues and lower wavelengths.

Regarding UV light and myopia. I have noticed that for the few days following significant sun exposure, even if wearing sunglasses, my vision is significantly worse. I believe that this is caused by irritation of the eye's tissue. Slight swelling of the cornea/lens would cause increased refraction and therefore increased blur. Sunglasses should be worn and even while wearing them, looking close to the sun, especially near mid-day should be avoided. If sunbathing, opaque eye covers like those worn while in tanning beds should be used.

Paper on the effects of blue LED light on photoreceptor cells:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4048889/

Infra-Red

Infra-Red (IR) light is the invisible light between visible red and radiative heat on the electromagnetic spectrum. It is a substantial component of all natural light sources - sunlight, moonlight, fire. With the exception of incandescent / halogen lighting it is largely absent in artificial light sources. As noted in the article on room lighting, LED and Fluorescent lights are devoid of IR light which is the main reason why these light sources are so efficient. More of their energy is being used to emit visible light rather than emit invisible IR and heat.

Even an overcast day with no direct sunlight provides large amounts of infra-red light into our eyes

There are specialized LED types which emit infra-red - a common television remote control has such a diode at the tip, which flashes a certain sequence to signal the TV to make changes. Similarly, night vision devices often use infra-red LEDs for illumination. This is a very narrow band of near infra-red (infra-red-A) which does not have any heating ability.

IR-A alone is not sufficient - the human physiology expects light to contain the full-spectrum, including mid and far infra-red (IR-B, IR-C), since this is the only type of light encountered in our evolutionary history. It is not understood in the mainstream that deficiency in infra-red leads to health problems, in particular problems with eye sight.

None of the display devices currently sold on the consumer market emit full spectrum light including infra-red, and we shouldn't expect manufacturers to start making such devices since they are all competing for energy efficiency. Emitting infra-red light, particularly long wave, costs significant amounts of energy.

Some decade(s) old projectors use halogen lamps which emit plenty of infra-red. Also, if using an E-ink device, you can use daylight or an incandescent lamp to light it..

It is possible to convert a standard LCD monitor to display the image using daylight or incandescent backlighting. After using such an Incandescent LCD for only a couple of months, I experienced dramatic improvement in my vision. I attribute this partly to the infra-red promoting regeneration of the eye's tissue. Also contributing to this fast vision improvement was the minimization of flicker and absence of blue/violet/ultraviolet light.

Article detailing the problems with LED and importance of infrared
https://articles.mercola.com/sites/articles/archive/2016/10/23/near-infrared-led-lighting.aspx

Motion Perception

The human visual system is able to perceive only a narrow range of the motion which exists in the physical universe. This is what makes slow-motion or time-lapse video so interesting, since it shows us motion which is normally outside the range of our perception.

We have evolved to follow moving objects with our eyes (known as tracking) which keeps the object in the same location on the retina. Objects not being tracked are perceived as blurred.

For a demonstration, hold your hand just above the keyboard and swipe it left and right. While tracking your hand, you will see it clearly, but the keys beyond will be blurred. If you stare at the keys while your hand is moving, the hand will be a blur. If you had an infinite rate of perception, both the keyboard and your moving hand would appear with perfect clarity. This limitation is understood as "persistence of vision". Some animals, particularly birds, are known to not have persistence of vision, or at least a very low persistence. In rare cases, humans have been known to lose their persistence of vision, which makes life in the modern world quite difficult. (Vasya from Ukraine had compiled some notes about such experiences.)

Now let's say you recorded a 60 FPS video of your hand swiping back-and-forth across the keyboard (assuming the environment is well lit and the frame exposure is very fast). You watch the video on a 60 Hz display with sample-and-hold refresh. You track the hand, and the motionless keys appear blurry, but as you track the hand it is blurred too! Why? Because your eye is moving with infinite smoothness across frames which are actually motionless, albeit for only 1/60th of a second at a time. Double the FPS/Hz and the hand will appear twice as sharp while tracking it, but the background will remain just as blurry as before. Keep doubling and the hand's sharpness will too. Eventually we will get to 960 Hz, where the hand will have a level of clarity similar to what is seen in reality. Experts in the field of VR have suggested that 1000 Hz sample-and-hold displays with 1000 FPS content will bring simulated motion close to reality for most people.

Motion appears more clearly with refresh types other than sample and hold. This is because the frame exists for a shorter time on the screen, which reduces the duration that the eye is tracking across a still frame.

Since we cannot reduce the persistence of our visual system, for better motion clarity with display technology, we need to reduce the persistence of the frames.

How this relates to eyestrain / myopia - the eye cannot actively focus on a blurred image, so if you spend significant amounts of time viewing blurry motion, i.e. watching content with constant full screen motion, you can not expect your vision to improve. If your eye is not strained by flicker, and has no issues focusing on flickering images, then it may make sense to use a display with a low persistence refresh for viewing this kind of content.

Rtings explains motion blur sample and hold
https://www.youtube.com/watch?v=vNb3X1AM6uI

Blur Busters motion test. Take your finger and follow the motion. Note that you can see your finger sharply, but not the moving image.
https://www.testufo.com/photo

Floaters

Floaters are typically experienced as dark blobs which drift around the field of view as the eye is moved. They follow eye motion with some lag due to inertia and can be very distracting.. Presence and visibility of floaters varies greatly from case to case, with some people having none or very few, and others with large ones which obstruct their vision significantly.

Floaters are often the result of the increased pressure on and deformation of the eye due to myopia The collagen suspended inside the eye's vitreous gel gets compressed into visible clumps It's also possible that bits of tissue break off from the eye's interior lining and become suspended in the field of vision (more common with older subjects). Some extreme cases have long "stringy" floaters stretching across the whole view or ring formations which block the central vision.

There are actually two visual aspects of the floater. The more prominent dark blob is the shadow of the floater, while the floater itself is much smaller and lighter in shade, resembling clear bubbles. However the two aspects of the same floater move in unison. This can be more clearly seen when squinting at a bright field, or while wearing pinhole glasses.

Treatment of floaters is still not mainstream. The least invasive procedure is laser treatment, called Vitreolysis, where the specialist fires a focused laser pulse directly at the larger floaters to break them up. Another, more invasive treatment is Vitrectomy (referred to as FOV, floaters only vitrectomy), where the eye's vitreous fluid, along with the floaters is exchanged with a clear saline fluid. Some experimental treatments involving enzymes which break-down the collagen are also being developed,. These procedures carry risks up to and including blindness, and should be researched thoroughly before commitment.

Diets rich in Hyaluronic Acid or supplementation can supposedly reduce incidence of floater formation.

Appearance of floaters can be prevented by minimizing the deformation of the eyeball - eliminating close focus as much as possible to prevent progression of myopia. I have observed that having a cold / flu with sinus inflammation, which put extra pressure the eyeballs can cause new floaters, so I recommend avoiding getting infected at all costs, especially if you are myopic.

If you experience large numbers of new floaters suddenly appearing, it could be a sign of retinal detachment, which is a medical emergency, and will lead to blindness if left untreated, seek medical attention immediately.

External Links:

video of floater in the eye:
https://www.youtube.com/watch?v=YcHK9X0jZFY

forum for discussion of floaters:
https://www.tapatalk.com/groups/floatertalk/

interesting page on floaters / treatment
http://www.eyefloatersdefined.com/

Neuritis

Early in the summer of 2013 an area of the central/lower vision in my left eye developed what resembled the after-effect of looking at a bright light. A kind of roughly oval shaped "burn-in", which remained constantly. It was not pronounced enough to block vision significantly, but it was worrying. I also had some pain when turning the eyes left or right, and when glancing sharply sideways it seemed like the "burn-in" became more intense.

My research online into the symptoms pointed to a condition called Optic Neuritis, where the optic nerve becomes inflamed.

I went to the optometrist for an exam and he could not see anything wrong with the eye. He told me that it could be Neuritis. He suggested resting the eye with cold compress. I was then referred to a retina specialist, who also didn't see anything wrong.

I should note that the condition manifested within a couple days of getting hit in the same eye by a large fly while bike riding. I believe that the fly germs triggered an immune response which eventuated in the optic nerve becoming inflamed. Both doctors told me that this was not the case, but I think they were wrong. I have had other cases where foreign germs had triggered auto-immune symptoms.

I did follow their directions, and resting the eye + cold compress seemed to help.

Using my large format LCD with CCFL backlight seemed to aggravate the condition, particularly in the evenings once there was less ambient light in the room. I started wearing amber tinted sunglasses while using the display which reduced aggravation of the eye.

Within a couple months the condition went away, and as of 2019 has not returned.

Sensitization

Sensitization is the process by which an individual gradually develops severe adverse reaction to a certain stimulus.

Eyestrain is typically experienced along with a gradual sensitization process. A common scenario goes as follows:

A user gets a new display device. At first, no symptoms are apparent. After a few hours or days of use, the user gets a feeling of tension in the head/eyes. After some days or weeks the symptoms worsen and appear after shorter and shorter periods of exposure. Eventually it may reach the point that the user cannot use the display without severe eye/head pain. Visible symptoms like red eyes may even develop.

It is common that even while away from the problem display, the user begins experiencing symptoms with other devices or light sources which never bothered them before.

Vasya's experience is an excellently described case study of display induced sensitization.

Unfortunately, it seems that sensitization of the visual system is very slow to reverse, especially since getting away from unnatural lighting is very difficult without taking extreme measures, i.e. becoming a hermit in the wilderness.

Due to the cumulative nature of sensitization, those experiencing it should do everything possible to avoid exposure to offending stimuli.

Cold / Flu & Eyesight

A few times when I have had a bad upper respiratory tract infection I noticed that my eyesight got worse for much of the duration. I believe that this was caused by the inflamed sinuses squeezing the eyeball, elongating it even more than it already is in its myopic state. I have also noticed new floaters after such an illness - unfortunately, it seems that this increased pressure can cause formation of new floaters.

There is nothing to gain from catching the cold or flu, and it is largely preventable with the usage of inexpensive personal masks and air filters while in the presence of infected persons (ideally, they are wearing one too). Of course, avoiding the presence of infected persons is the best course of action. (My experience is that people are still contagious for at least a week after the main symptoms have passed.)

Unfortunately, the pharmaceutical/medical establishment promotes the myth that cold and flu are spread from surface contact. This is rarely the case as long as you are not in the habit of putting unwashed fingers into your eyes, nose and mouth. It is more profitable to treat cold and flu with medication than to prevent it, so the mass market has no incentive to promote effective preventative measures (the flu shot, by the way, has not demonstrated a statistically significant benefit)

Upper respiratory tract infections are airborne, i.e. the virus travels from host to host via the water droplets of the infected person's breath. Picture a cloud of someone's breath, visible on a cold winter's day - it is present in warm temperatures too, we just can't see it, and with an infected person each breath is teeming with virus particles. Any fabric or filter material which the droplets must pass through will stop some droplets - even a scarf can protect you - the more layers, the better. I can also personally recommend nasal air filters for discrete protection. The brand I have used is WoodyKnows - "tested" them sharing a car with an infected person, and I did not get sick, while every other time I've shared a car with an infected person I did get sick.

If your immune system is healthy, passing a coughing stranger in the street or hall will be unlikely to affect you - this can be thought of as "background radiation". It's when you spend a few minutes up close with an infected person that you receive a "lethal dose" (continuing the radiation analogy), i.e. a count of virus particles in your system which overwhelms your immune system and causes a full-blown infection. The virus has evolved to trigger this full-blown infection, which is an overreaction of the host immune system, which multiplies its chances of spreading. What constitutes a "lethal dose" varies from person to person. If you get that "lethal dose", no amount of garlic, vitamin C, can prevent full blown infection - they may raise the quantity that constitutes a lethal dose, but they must be taken well in advance to the time of exposure. A virus is a physical microorganism, it must be physically removed by your immune system.

There are measures that can be taken to prevent full blown infection. If you know that you have been exposed, immediately warm yourself. Put on your coat, hat, etc. even if you are indoors and don't feel cold. When you are home, lay clothed in bed and cover yourself with blankets. The extra warmth gives the immune system an energetic boost. Chills are a common early symptom of infection, they happen because the immune system is sapping more energy than usual from the body to aid its fight.

There is a reason why the body induces fever during illness. Inducing a "fever" pro-actively by warming ones-self has the same benefit, with much less suffering, and the fever is under your conscious control - of course, be careful not to overdo it since overheating the body significantly is dangerous.

Also very important is to breath through layers of scarf or collar to warm up your breath. Drink warm fluids and avoid cold food/drink. The reason that cold/flu proliferates in the cold seasons is that the immune system is suppressed in a cold throat - and this is typically the first location of attack, the throat! Any irritation to the throat will increase the chances of full-blown infection, this includes coughing and speaking - yes, the act of speaking damages cell walls, providing easy-access breeding grounds to the virus. Warming the air also helps prevent cough.

Coughs usually begin as a mild tickle in the throat. Coughing or "clearing the throat" seems to provide temporary relief to the tickle, but will actually increases the intensity of the tickle/irritation with every cough/throat-clearing. Eventually this leads to a persistent cough which can last for weeks after the illness passes. Therefore, it is best, and entirely possible, to resist that initial temptation to cough. For brief moments it can be very difficult - I recall times when the tickle was so strong that tears were coming out of my eyes, but I resisted. That urge soon passed and I had no cough, even if I had succumbed to the illness otherwise - snot, fevers, etc., but no cough! Reflecting now, it seems that I had no cough for at least the past 4 illnesses due to resisting the urge.

Also very important is to rest. Exertion weakens the immune system temporarily, and the virus will exploit any temporary weakness.

I have been on the very edge of getting sick multiples times, but managed to turn the tide by taking these measures. Sometimes even taking a day just to rest in warmth when I knew that I was exposed - better a day in bed while mostly healthy than a week in bed while sick! The immune system can only be reactive, but your brain can be pro-active, so use it to your advantage!

A few times in recent years I have slipped-up and held the infection at bay for days, only to overexert myself, or run into someone who was sick and not get away in time. Once I even ate some overly spiced food, and the throat irritation led to full-blown infection. It happens... if you get the full-blown infection, the best course of action is to stay warm in bed. Trying to go about your life normally will only prolong your discomfort. In the meantime you will be infecting multiple other people.

I have found that resting on an incline reduces sinus pressure and therefore eye pressure.

I have sometimes made the mistake of returning to work/school too soon. Take the extra day and recover fully because relapse can be considerably worse than the initial illness that was almost defeated.

If everyone took such measures, the cold and flu would become a thing of the past, or something that someone suffers once or twice in their life, not an annual or biannual occurrence.

Resources

Share your thoughts and experiences on the forum:
forum.techoptica.net

Archive of Vasya from Ukraine's page on "Monitors and our Health"
techoptica.net/vasya.html

LEDstrain community for those dealing with LED/display sensitivity issues:
https://ledstrain.org/

Blur Busters community focused on improvement in display motion handling: https://www.blurbusters.com/
Useful test patterns for motion by Blur Busters https://www.testufo.com/