What causes eye strain when viewing any display?

What causes eye strain when viewing any display?

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Few everyday experiences:

  1. Staring at the physical paper (or any other sight in nature) doesn't cause eye strain.
  2. Staring at the LCD screen causes eye strain.

Some of the differences in properties I have isolated so far are:

  1. Refresh rate, that how often picture updates itself. For LCD like display, it is finite, but for the physical paper (viewing up, down or turning page) it is instantaneous (infinity),

  2. Most common LCD emits backlight to project image, whereas physical paper reflects light.

  3. Other effects like glare, blue light (harmful light which disturbs sleep cycle) which is absent in physical paper but present in most of the LCDs.

(3.1) The physical paper doesn't distort contrast or image quality whereas LCD can sometimes. Although I am not sure how giving an inaccurate description (which is a different problem) can cause eye strain.

So I want to ask what makes up a favourable viewing experience from a biologist perspective.

Any task that implies an intense use of the eyes may cause eye strain. The difference between reading paper and staring at a screen may vary from the distance, pauses made when turning the page, etc…

As stated in this link, it depends on the individual. So a favorable viewing experience is any that does not require an intense effort given the particularities of the subject's vision.

"Some people, while concentrating on a visually intense task such as reading fine print, using the computer for hours at a time, or trying to see in the dark, unconsciously clench the muscles of their eyelids, face, temples, and jaws and develop discomfort or pain from overuse of those muscles. This may lead to a vicious cycle of tensing those muscles further and causing more distress. Other people attempting to do similar visual tasks may have no symptoms at all."

How computer glasses can ease digital eye strain

According to The Vision Council, a recent survey of more than 10,000 adults found that 65 percent of Americans experience digital eye strain symptoms — such as dry, irritated eyes, blurred vision, eye fatigue and headaches — when using a computer, smartphone and other digital devices.

And eye strain and other symptoms of computer vision syndrome don&apost occur only in adults. Millions of children work at a computer every day, either at home or in school. Prolonged computer use can stress a child&aposs eyes and may affect normal vision development.

Digital Eye Strain

According to the American Optometric Association, digital eye strain encompasses a wide range of symptoms. In addition to visual fatigue, digital eye strain also includes symptoms such as:

While these symptoms are usually temporary, if left untreated, they could potentially worsen over time.

Digital eye strain also costs businesses thousands of dollars in lost productivity every year. According to the Optometry Times, eye-focusing problems cost businesses more than $2000 annually per employee.

What Is On-Screen Flicker and How Does it Harm Your Eyes?

The harmful intensity and energy of blue waves isn’t the only thing you need to think about when selecting a computer monitor. Flicker also presents a genuine danger to the health of your eyes.

Monitors that use LED backlighting flicker through pulse-width modulation (PWM), which enables you to adjust the brightness of your screen easily. If you’re in a sunlit room, you’ll need a bright screen to help you see when you’re working late at night, you may prefer to dim your screen accordingly.

PWM turns the backlight “on” and “off” quickly at a steady frequency, which decreases the brightness of the screen. This seems like it should be a good thing since you want to be able to fully control the brightness of your screen to adapt to fit your environment and your personal preferences.

The problem is that the computer screen flickers at a very fast rate imperceptible to the human eye as the backlight turns on and off. This flicker causes your pupils to rapidly move from larger to smaller, which in turn causes a multitude of eye issues, including eye strain and eye fatigue.

What too much screen time does to your eyes

As people of all ages are spending more hours focused on digital screens, their eyes are getting an exhausting endurance workout.

Eye strain from hours of screen time can result in eye irritation, dryness, fatigue or blurred vision, and such problems are increasingly common, according to a new report.

"Some of us are using these things for up to nine hours a day. Your eye muscles have to focus at that near range and that can be fatiguing," Dr. Christopher Starr, an associate professor of ophthalmology at Weill Cornell Medical College in New York, told CBS "This Morning."

"You can imagine if you were at the gym and you held a dumbbell, your bicep would be extremely sore nine hours later. Same thing for your eyes, you have to take breaks to relieve those muscles," he said.

A vast majority of American adults surveyed -- 93 percent -- spends two hours or more per day in front of some sort of screen, from televisions to computers to smartphones to e-readers, according to the report by The Vision Council, an advocacy group for optical manufacturers and distributors. Sixty-one percent said they spend five or more hours and 30 percent said they look at screens more than nine hours per day. The group surveyed more than 9,700 U.S. adults.

The range of media devices the respondents were using was broad. Sixty-nine percent of people reported used smartphones, 58 percent used laptops, 52 percent used a desktop computer and 43 percent used a tablet or e-reader. Seventy-seven percent said they watched television.

The Vision Council

Most digital screens are backlit and emit blue light, or high-energy visible (HEV) light wavelengths, which the group said can cause irritation and possibly long-term damage to the retina. Blue light is also known to suppress the sleep hormone melatonin, causing an artificial feeling of wakefulness and disrupting sleep patterns, which can add to eye strain.

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Dryness, caused by reduced blinking while staring at screens, is also a common factor in digital eye strain. A person's blink rate -- normally about 15-20 times per minute -- can decrease by up to half when people are fixated on what they're viewing on a screen.

"When you're not blinking, and you're staring and your eyes are wide open, tears evaporate very quickly," Starr said. "You get dry spots, blurred vision, it can cause redness, pain, and over the course of the day it just worsens and worsens."

Just like other muscles in the body, the eyes need a varied "workout" and some respite from prolonged strain.

"What we recommend to reduce this -- what's called computer vision syndrome -- is to follow something called the 20-20-20 rule," said Starr. "Every 20 minutes that you're on a computer or a mobile device, look away from the computer at an object at 20 feet away or further for 20 seconds or more. And that will let those eye muscles relax."

Anti-reflective lenses on eyeglasses or filters for screens can also help absorb some of the blue light and limit how much reaches the retina and into the central nerve of the eye.

People with myopia, or nearsightedness, and other vision issues like hyperopia, astigmatism and presbyopia, may be at increased risk for digital eye strain. The National Eye Institute says that myopia has become much more common in recent generations. More than 34 million Americans have myopia, projected to reach 40 million by 2030.

In addition to taking breaks from focus on digital screens and using eyewear, doctors recommend adjusting light exposure to help with eye strain, both indoors and outdoors.

Contrary to popular opinion, more indoor light may actually be worse for reading, when it's on a screen. Too much light competing with the device's light creates glare. And a bright, white background is also worse than a cooler, gray tone.

Getting enough outdoor light is also critical to helping eye muscles develop and stay healthy.

Though the highest reports of eye strain are from the groups who likely use the screens for work the most -- Millennials and Generation X -- children are also a concern. The report says more than 23 percent of kids use digital screens more than three hours a day.

"One of the newest studies I've seen actually shows that the kids -- when you're doing all this reading and using computers, you're indoors," said Starr. "There's some evidence that you need some natural light, for the eye's maturity and if you don't have that natural light, the eyes might get longer and more near-sighted."

"The computers aren't going anywhere, mobile devices aren't going anywhere, " he added. "They're very useful, obviously. We're not saying don't use them, we're saying when you do use them, use them wisely and smartly."


Usage of digital devices for work and social purposes, often for many hours each day, is now normal among individuals of all ages. While there are challenges in determining the prevalence of DES, levels of 50% or more have been reported in numerous published studies, indicating that a large proportion of the population are at risk, and may seek advice and/or treatment linked to the condition. Eye care professionals are well placed to advise on DES, with professional bodies such as the College of Optometrists (UK) and the American Optometric Association providing some guidance for practitioners. To provide optimum patient care related to the condition, it is essential that eye care practitioners are well informed regarding DES and the growing evidence base in this field.

DES symptoms may be split into those linked to dry eye (external symptoms), and internal symptoms related to ametropia, accommodation or vergence problems. Accommodative and/or vergence issues with computer use seem to be a consequence of demanding near work, rather than screen use per se. Nevertheless, such symptoms still require management to promote comfortable viewing. Treatment of dry eye, even mild cases, may have a substantial influence on comfort with screen use.

Questionnaires are of value in evaluating DES as they are simple to implement and capture patient experiences, although validated instruments are rare. In evaluating putative DES treatments, questionnaires have frequently been used alongside objective measures linked to VF, although correlation between objective and subjective assessments has not always been apparent. Regardless of the type of intervention proposed (eg, management of dry eye, correction of refractive error, use of computer spectacles or blue-blocking lenses), persistent effects of treatment should be explored to indicate the true value of DES management options. With the high prevalence of DES and near-universal use of digital devices, it is paramount that the condition is considered by eye care practitioners, and treatment options are supported by available research evidence.

Is viewing a computer screen for most of the day harmful to vision?

Everything I've heard on the subject is just anecdotal/speculative, so I was wondering if there have been any long term studies on the effects of looking at a computer screen for a large portion of the day. Or if there is a scientific basis for the idea that staring at a computer screen, or any object a fixed distance from your face, for the majority of the day can weaken your vision in any way?

I've heard advice that we should look out the window and into the distance every so often when using a computer for long periods of time, but is there any proven benefit to this?

Also, a friend mentioned that there are tribal populations with superior long-distance vision to us first worlders. Is this true? Would it be due to us not utilizing our long-distance vision as much as them, or more selection pressure on the tribal populations to have better vision, or both?

Does the same apply to reading books?

That's why after awhile you blink and it burns a little or you close your eyes and they burn for a sec or water up a bit.

I regularly work/play on computer screen for 10-14 hours daily for years and have never experienced this. Are some people more prone to this?

Towards the end of the day, if you're spending long hours on the computer, you may notice your vision get increasingly difficult to manage, or hard to focus.

I also never experienced this. I just get tired because it's getting late, but my eye movement subjectively seems the same as in the morning (well at least after my 30-60 minute wakeup phase). Again: Are some people more prone to tired eyes?

Also, I read somewhere that the relaxed focal distance of the human lense is somewhat between 20-30 cm in front of the eye. Why does staring in the distance help when the lense isn't relaxed? Is it because of the convergence muscles of the eyes?

When you say stare at something in the distance, could you also just "stare" into space "through" your computer screen? I feel like this is the same thing as focusing on something far away, because it feels relaxing and makes up close things blurry obviously

Question: I work with computers all day, and sometimes when I come home, I feel like the "muscles" behind my eyes hurt. Like, I have to close my eyes or look at something that's not a screen in order to "relax" them. My wife says I am "straining my eyes."

Do you know what's actually going on?

Is this eye damage from dry eyes reversible?

Thanks! I don't want to derail anything but recently I've lost a bunch of eyesight due to an eye infection. The vision loss I can deal with (one eye isn't so bad) but now computer screens blur my vision forcing me to squint to see. I was pretty freaking worried about further damage but you've reassured me. Thank you Dfunk3d.

I just had a thought and I'm wondering if these are out there. Are there any glasses (non-corrective or corrective) than have inward facing lenses so that the light coming from the screen close to your face comes straight to your eyes, making it easier for them? Or is there something wrong with the physics of my thoughts?

Is there a difference between glossy and anti-glare displays? I personally find glossy displays way more stressful to look at as there are always reflections in there when I've got something black on the screen (eg apple 24'' cinema display and textmate)

Hi, my teacher that has been working in digital media since she was 20 (she's 66 now) said that not taking care of your eyes can cause a yellow at the tear ducts. do you know how this can be prevented?

I remember learning in Biology class that the muscles in your eyes wear out after years, due to which the elderly often need reading glasses because they can't focus on close objects anymore.

Could the excessive straining of these muscles (as done by looking at a computer screen for 8 hours) potentially accelerate this effect?

I was having vision problems for exactly this reason. I initially thought I might have an eye infection or something, but I went to an eye doctor and was told that one of my eyes has a slight difference in vision from the other, so by the end of the day I'm just exhausted from the effort of trying to focus. He gave me a prescription for computer glasses, which are like reading glasses but more specifically for focusing at about the distance of a computer monitor. One lens has no prescription, and the other has a 0.75 prescription. Also, they have anti-glare coating and a slight amber tint. I'm actually waiting for them to arrive, so I can't report yet how well they work, but I'm very excited to try them.

I look at 8 screens surrounding me all day -_- I can confirm this man's analaysis. Blink offten and look away to relax your eyes, I would also recommend if you can manage it, that you go outside for a few minutes every hour or 2 and just let your eyes relax.

I've heard it suggested that something called the 20/20/20 rule could potentially prevent any harm on your eyes. Every twenty minutes you should look at something for 20 seconds that is twenty feet away. I'm assuming that it has something to do with keeping the muscles that focus the eye flexible.

My optometrist explained another way in which staring at a monitor for long hours causes eye strain:

Since the plastic which makes up the outermost layer of the screen has some thickness to it, and since it is not perfectly transparent, the eye constantly switches focus between the image behind the plastic and the surface of the plastic itself. This effect is worse if the plastic is dirty because the eye then has more to focus on.

He made it sound as if overtime this can actually cause a worsening of vision.

I've read a study that FPS games can actually improve your vision. I'm from a family of 7 and I'm the only one without glasses, I've also spent the most time in front of a computer. 20/20 vision.

To piggyback, my eyes don't have the exact same focus and it was leading to lots of strain as my eyes "fought" each-other to be in focus. (this was how the Optometrist described it).

Got myself a pair of glasses for use while reading and using the computer and my headaches have disappeared. Both Optometrists told me that if it wasn't for the amount of time I spent doing near-field work I wouldn't have an issue. I don't on days when I'm not at my computer but definitely notice a few hours later if I forget to put my glasses on at the computer.

20 years) I was in the process of buying prescription glasses. I generally do not wear glasses as I feel I have fairly decent vision. But extremely large lecture halls and seeing the board from what seemed to be 100 yards away was becoming an issue. The person selling me the glasses suggested some kind of special coating be applied for an extra cost. This coating, IIRC, was supposed to block some bad radiation that I was getting from being in front of a computer all the time. According to the salesperson, this was destroying my eyes and I needed this. I declined because it seemed like an add-on just to inflate the price. Snake oil, in other words. In your opinion, did I make the correct decision? As far as I know, my vision remains in a good condition and I have not developed eyeball cancer. I spend more time in front of a computer these days as my career dictates that I do.

So Gunnar's actually do work for what they advertise? I've read that they are optometrist approved, but I couldn't justify the price without actually having some sort of proof that they will actually help you with eye strain.

ive discovered wow last year.. (please no comment regarding my careless decisions) and ive been on the computer 'multiple' hours a day since last year. About 3 months ago i realized i cant see the board from the back of the classroom anymore and i needed to get glasses. so what im trying to get at is.. youre telling me wow is not actually making me blind? :D

As an Optician, I get to deal with this question all the time. I've found that this is the best answer. Just like your mother telling you not to sit too close to the TV, the relationship between extended computer use and damaged vision is unfounded. Naturally, we were not mean to stare at screens all day, so until we evolve to become more comfortable with monitors, we have to adapt and be resourceful. Our eyes are at a full relaxed state when we stare out into optical infinity, and for us to accomodate up close for extended periods of time, it requires a tremendous amount of energy. (This is why we tend to fall asleep quickly when we read in bed)

It should also be noted that our blink rate drops significantly when on the computer, which contributes to dry eyes. As the conjunctiva layer starts to dry, it will blur our vision, so this just adds to all the issues, making you miserable.

If you are currently a glasses wearer, an Anti-Reflective layer is critical for computer users. The AR coating eliminates nearly all reflections on the surface of the lens, providing you with much clearer vision than without it.

Staring at the monitor all day may induce a temporary myopia, which could confuse you and throw you off completely.

The best way to prevent any vision trouble for those of you glued to the desk, is to look twenty feet away for twenty seconds, every twenty minutes. Give the muscle inside the eye a break, and effectively yourself a break too.

Eye Strain

The term eye strain is frequently used by people to describe a group of vague symptoms that are related to use of the eyes. Eye strain is a symptom, not an eye disease. Eye strain occurs when your eyes get tired from intense use, such as driving a car for extended periods, reading, or working at the computer. If you have any eye discomfort caused by looking at something for a long time, you can call it eye strain.

Although eye strain can be annoying, it usually is not serious and goes away once you rest your eyes. In some cases, signs and symptoms of eye strain are a sign of an underlying eye condition that needs treatment. Although you may not be able to change the nature of your job or all the factors that can cause eye strain, you can take steps to reduce eye strain.

What causes eye strain?

The medical term for eye strain is asthenopia. The symptoms of ocular fatigue, tired eyes, blurring, headaches, and occasionally doubling of the vision are brought on by concentrated use of the eyes for visual tasks. Some people, while concentrating on a visually intense task such as reading fine print, using the computer for hours at a time, or trying to see in the dark, unconsciously clench the muscles of their eyelids, face, temples, and jaws and develop discomfort or pain from overuse of those muscles. This may lead to a vicious cycle of tensing those muscles further and causing more distress. Other people attempting to do similar visual tasks may have no symptoms at all.

Common precipitating factors for the onset of eye strain include extended use of a computer or video monitor, straining to see in very dim light, and exposure to extreme brightness or glare. Many people will blink less than normal when performing extended visual tasks. This decreased blinking may lead to dryness of the ocular surface and symptoms of dry eyes.

Refractive errors (a need for glasses for distance or near vision, or both) may produce the symptoms of eye strain.

The inability to make both eyes work together in a binocular fashion may also generate the symptoms of eye strain. However, most individuals who have limited or no binocular vision have no such symptoms.

In people who already have headaches or blurring of vision due to eye strain, symptoms may be worsened by an underlying eye problem such as an eye muscle imbalance or a need for glasses for the correction of myopia, hyperopia, or astigmatism. Wearing glasses with an incorrect prescription may cause eye strain. In those who already have eye strain, not getting enough sleep, certain medications, being under stress, or being fatigued can also make those symptoms worse.

Eye Strain Symptoms: Eye Pain

The eye is the organ of sight. Eye pain can be cause by conditions involving the eyeball (orbit) or be caused by conditions of structures around the eye.

The eye has a number of components. These components include but are not limited to the:

  • cornea,
  • iris,
  • pupil,
  • lens,
  • retina,
  • macula,
  • optic nerve,
  • choroid, and
  • vitreous.

What are the symptoms of eye strain?

If one asks patients who complain of eye strain to define what they mean by that term, they may describe nonspecific soreness of the eyes, mild tearing or dryness, blurring of vision, soreness of the back of the neck, doubling of vision, light sensitivity, difficulty focusing on images, tightness of the temples, forehead, brow area, or back of the head, or combinations of all of these. Headache is the most common symptom. It is usually mild, located in both temples, not pounding, and often relieved by stopping the visual task.

What are the signs of eye strain?

The diagnosis of eye strain is made by a physician on the basis of the history as described by the patient and the absence of any serious eye disease. There are no specific tests to prove that the symptoms are indeed due to eye strain. There are no methods to objectively measure the degree of eye strain.

You should see an ophthalmologist if you have ongoing pain in the eye, visual loss, redness, or irritation of the eyes. These symptoms cannot be explained by eye strain. In general, if your eye strain is not relieved by resting your eyes, an eye examination should be performed. If you are examined by your ophthalmologist for your symptoms of eye strain, he or she will do an examination, including checking to see if you need glasses. If the doctor feels glasses may make your eyes more comfortable, these will be prescribed.

Symptoms of eye strain are unusual in children under 12 years of age. If your child complains of headaches after reading, eye fatigue, blurring of vision, or double vision, a visit to an ophthalmologist is warranted to rule out any underlying eye condition.


How do health care professionals diagnose eye strain?

Eye strain is diagnosed on the basis of the history that the patient provides and the absence of any serious eye disease.

What is the treatment for eye strain?

Eye strain is extremely common. As computer use has become commonplace, more people are experiencing what has been termed "computer vision syndrome," which is synonymous with eye strain. In most of these people, the symptoms are mild and they are aware that their feelings of the eyes being "tired" can be relieved by briefly closing their eyes and taking a break from the visual task they are performing. The symptoms will often be absent or markedly reduced on days when computer use is more limited.

Although eye strain is uncomfortable, there are no long-term consequences of eye strain. There is no evidence that eye strain causes any adverse changes in the eyes. There is also no evidence that, in adults, continuing to do visual tasks while experiencing eye strain will result in any structural damage to the eyes.

Eye strain, however, can be unpleasant and disruptive to your ability to concentrate and work. The symptoms of eye strain may lead to physical fatigue, decreased productivity, increased numbers of work errors, and anxiety.

If you feel that you are experiencing eye strain after extended reading, try to adjust your lighting to maximize illumination while minimizing glare, take frequent brief breaks from the visual task, and consciously blink a few extra times. Firmly massaging the temples with your fingers in a rotary fashion for a minute while closing your eyes is often helpful in relieving the symptoms.

If you experience eye strain while working at your computer, increasing the resolution of your screen (CRT) and reducing ambient lighting may be helpful. Adjusting the distance of your eyes from both the computer screen and your reading material may also relieve your symptoms. Changing brightness and contrast levels on your monitor and increasing text size can also be advantageous. Rather than keeping your eyes focused on the computer screen for hours at a time, interrupt this process every 15 minutes by briefly looking out of the window or around the room.

When performing extended visual tasks of all sorts, occasionally stand up, move about and stretch your arms, legs, back, neck, and shoulders.

If the symptoms of eye strain are predominantly those of dryness and increasing your blink frequency is not helpful, using an over-the-counter tear substitute a few times a day can be efficacious.

If all these home treatments don't work to relieve your eye strain symptoms, see your ophthalmologist.

Choose the right display panel

When it comes to the display panels, the type significantly affects the quality of the picture and also the amount of stress on eyes. Display panels are of three types

  • Twisted Nematic or TN
  • In Plane Switching or IPS
  • Vertical Alignment or VA

The right display panel for eyes IPS or VA

When it comes to gaming, TN is an ideal choice for the display panel, but it is damaging to the eyes. IPS display panels, though they are costly, are friendly to the eyes and are less straining. VA displays come close to the IPS display and is an alternative to the IPS. However, continuous hours spent on any display will cause eye strain.

A Close Look at Our Eyes

More than most other animals, we rely on sight to gain information about our surroundings. Other animals are wired to their sense of smell. As such, human eyes have a different complexity than the eyes of other animals, with the eyes collecting the information and the brain interpreting them.

The eye is a ball separated into two chambers by the iris and crystalline lens (Figure 1-1). The outer surface, the sclera is white except for its anterior clear part, the cornea, delimiting, with the iris and crystalline lens, the anterior chamber filled with a clear fluid called the aqueous humor. The posterior chamber is filled with a more viscous substance called the vitreous humor which helps to regulate the eye pressure and its shape. Lining the inside of the sclera, in the posterior chamber, is the choroid, a vascular layer, containing connective tissues. And inside of the posterior chamber, against the choroid is the retina, formed during the fetal development of the brain, which contains the eye’s sensory cells and photoreceptors. 1

The photoreceptors of the retina are rods and cones. There are about 120 million rods in an eye, responsible for the scotopic vision, or vision in low level of light. Rods are sensitive to shape and movements, but are not sensitive to colors. Cones, located in the macula, are the photoreceptors sensitive to colors. There are about 6 million of three different types of cones with sensitivity to blue, green, and red, and of different abundance. There are more red cones than green and blue cones. The distribution of cones in the macula and fovea also differ as a function of the wavelengths they absorb.

Along with rods and cones, a third type of photoreceptors are present within the retina. They are the intrinsically photosensitive retinal ganglion cells (ipRGCs). Photosensitive because of the melanopsin they contain, a light sensitive protein, ipRGCs are involved in non-image forming signal transmissions to the brain. They help regulate circadian rhythm, pupil constriction, mood, alertness and more body functions.

Color Sensing

Color sensing and visual perception occurs when light in the 380–780 nm range hits the retina. Ultraviolet and infrared wavelengths are not absorbed by the retina, but by the outer layers of your eyes , the cornea and lens. In a normal eye, light enters the eyes through the cornea, and passes through the pupil. The iris around the pupil regulates the amount of light entering the eye by getting bigger or smaller. As the light hits the lens, the zonular fibers and ciliary muscles change the shape of the lens in order to focus and maintain the light on the retina where the photoreceptors are located. Cones and rods convert the light into electrical impulses transferred by the optic nerve to the brain, which interprets the signals as an image.

Colors are defined by their wavelength and frequency. Different wavelengths are perceived by the eye as different colors. Rods and cones contain photopigments made up of a protein component (opsin) and a chromophore (retinal). The opsins of the rods and cones are different and make rods and the three types of cones sensitive to different ranges of light wavelengths. See Figure 1-2. Upon photoexcitation, the retinal contained in the photoreceptors changes, triggering a cascade of reactions as part of the visual signal.

With the cones centered on the wavelengths corresponding to blue, green and red, the brain interprets the signals sent by the overlap of different cones into various colors, with white being interpreted from the stimulation of the three cones and yellow for example, from the stimulation of green and red cones. Conditions such as color blindness are due to genetic mutations causing abnormalities of the cone pigments.

20/20 Vision

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance.

The cornea facilitates the focusing of an image on the retina. Adjustments for distance are realized through a change in the lens shape, which is called accommodation. The process of accommodation is carried out by the contraction of the ciliary muscles and the zonular fibers connecting this muscle to the lens.

The shape of the eyeball, along with the focusing power of the crystallin lens and the cornea, plays a role in projecting a crisp image on the retina. An eyeball too long or too short will change the place where the image focuses, before or after the retina, hence causing refractive errors such as nearsightedness (myopia) or farsightedness (hyperopia). Other vision defects such as astigmatism can occur when either the lens or the cornea does not have an optimal spherical surface.

Vision Problems

With aging the lens stiffens and leads to a loss of accommodation manifested by presbyopia. Prespyopia is a condition where it is increasingly difficult to focus on near objects, despite corrective lenses. Aging can also lead to an opacity of the crystalline lens, a common eye disorder called cataract.

Other deteriorations of the eye include glaucoma, a group of eye diseases characterized by an increase of pressure within the eyeball. 2-3 The buildup of pressure converges on the optic nerve, the weakest point of the sclera where the nerve leaves the eye. This can lead to the death of the retinal cells and degeneration of the nerve fibers, finally resulting in permanent vision loss.

Another cause of vision loss is macular degeneration. 4 It is caused by the damage of cells and photoreceptors located on the macula, where the vision is focused and characterized by the presence of large drusen (extracellular material) and pigmentary abnormalities in the macula. There are two types of macular degeneration, wet and dry, and several stages of development of the disease. The specific factors of macular degeneration are still to be completely understood even though genetics, race, age and a long-term exposure to sunlight and in particular the action of the blue component of the light had been evidenced as causative factors.

According to the World Health Organization (WHO), upwards of 1.3 billion people worldwide have some sort of vision problem. 5 The WHO report indicates that 80% of all vision problems are preventable.

The leading causes of vision problems globally include:

  • Accidents and Injury
  • Uncorrected refractive errors
  • Cataracts
  • Age-related macular degeneration
  • Glaucoma
  • Diabetic retinopathy
  • Corneal opacity
  • Trachoma

A National Institute of Health study estimates that ninety million adults over forty years of age in the United States experience vision problems. Almost everyone has some degree of presbyopia by this age. 6

The NIH summarized some findings from eye care professions, and projects some alarming trends, as seen in Table 1-1. Some of this is due to aging populations, but others appear to be caused by external factors.

The Blue Light Hazard

Blue light is a part of the visible light spectrum that has been shown to contribute to digital eye strain. High-energy blue light from device screens combined with the amount of time we use devices may cause overexposure, and affect our eye health. As shown in Figure 1-3, our eyes transmit various bands of visible light differently as we age. Young children do not filter as much blue light, for example, as older children. Older adults transmit less.

Chad Dockter, OD attended the University of Minnesota from 1985-1989 to study Biology. He then attended Illinois College of Optometry in Chicago in 1989 and graduated in 1993. At Illinois College of Optometry he completed an externship at Low Vision Resources in Minneapolis. Specialty areas include family eye care, refractive surgery and pediatrics.

Chris Freed, OD graduated from Michigan State University in 1993 with a major in biology and a minor in ecology. Dr. Freed graduated from Illinois College of Optometry in 1997.


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