COMPUTERS AND THE EYE
Text by Terence Moss
(GLOBE MAGAZINE SEPTEMBER 2020)
We are all spending a large part of our day looking at smartphones, tablets and computer screens. Are they damaging our eyes? Many of us are experiencing ‘Computer vision syndrome’, also referred to as digital eye strain, describes a group of eye and vision-related problems that result from prolonged computer, tablet, e-reader and cell phone use. Many individuals experience eye discomfort and vision problems when viewing digital screens for extended periods. An average office worker will spend 1,700 hours per year in front of a screen. Then add the hours addicted to using our phones all day long. All of that screen time seems to come with various ill effects on our bodies and minds, such as eye strain, headaches and insomnia.
The light spectrum
Without getting into complicated physics, there is an inverse relationship between the wavelength of light rays and the amount of energy they contain. Rays on the red end of the visible light spectrum have longer wavelengths and, therefore, less energy. Rays on the blue end of the spectrum have shorter wavelengths and more energy.
The electromagnetic rays just beyond the red end of the visible light spectrum are called infrared — they are warming, but invisible. (The “warming lamps” you see keeping food warm at your local eatery emit infrared radiation. But these lamps also emit visible red light so people know they are on! The same is true for other types of heat lamps.)
On the other end of the visible light spectrum, blue light rays with the shortest wavelengths and highest energy are sometimes called blue-violet or violet light. This is why the invisible electromagnetic rays just beyond the visible light spectrum are called ultraviolet (UV) radiation.
The dangers and benefits of UV
UV rays have higher energy than visible light rays, which makes them capable of producing changes in the skin that create a suntan. In fact, the bulbs in tanning booths emit a controlled amount of UV radiation specifically for this reason. But too much exposure to UV causes a painful sunburn — and even worse, can lead to skin cancer. These rays also can cause sunburned eyes — a condition called photokeratitis or snow blindness.
Ultraviolet radiation, in moderation, also has beneficial effects, such as helping the body manufacture adequate amounts of vitamin D.
Key points about blue light
1. Blue light is everywhere.
Sunlight is the main source of blue light. Being outdoors during daylight is where most of us get most of our exposure to it. But there are also many man-made, indoor sources of blue light, including fluorescent and LED lighting and flat-screen televisions. Most notably, the display screens of computers, electronic notebooks, smartphones and other digital devices emit significant amounts of blue light. The amount of HEV light these devices emit is only a fraction of that emitted by the sun. However, the amount of time people spend using these devices and the proximity of these screens to the user’s face have many eye doctors and other health care professionals concerned about possible long-term effects of blue light on eye health.
2. HEV light rays make the sky look blue.
The short-wavelength, high-energy light rays on the blue end of the visible light spectrum scatter more easily than other visible light rays when they strike air and water molecules in the atmosphere. The higher degree of scattering of these rays is what makes a cloudless sky look blue.
3. The eye is not very good at blocking blue light.
Anterior structures of the adult human eye, the cornea and the lens, are very effective at blocking UV rays from reaching the light-sensitive retinaat the back of the eyeball. In fact, less than one percent of UV radiation from the sun reaches the retina, even if you aren’t wearing sunglasses.
Remember though that sunglasses that block 100 percent of UV are essential to protect these and other parts of the eye from damage that could lead to cataracts snow blindness, a pinguecula and/or pterygium and even cancer. Virtually all visible blue light passes through the cornea and lens to reach the retina.
4. Blue light exposure may increase the risk of macular degeneration.
The fact that blue light penetrates all the way to the retina (the inner lining of the back of the eye) is important, because studies have shown that too much exposure to blue light can damage light-sensitive cells in the retina. This causes changes that resemble those of macular degeneration which can lead to permanent vision loss. Although more research is needed to determine how much natural and man-made blue light is “too much blue light” for the retina, many eye care providers are concerned that the added blue light exposure from computer screens, smartphones and other digital devices might increase a person’s risk of macular degeneration later in life.
5. Blue light contributes to digital eye strain.
Because short-wavelength, high energy blue light scatters more easily than other visible light, it is not as easily focused. When you’re looking at computer screens and other digital devices that emit significant amounts of blue light, this unfocused visual “noise” reduces contrast and can contribute to digital eye strain. Lenses that block blue light with wavelengths less than 450 nm (blue-violet light) increase contrast significantly.
Therefore, computer glasses with yellow-tinted lenses may increase comfort when you are viewing digital devices for extended periods of time. These special-purpose glasses are available without an eyeglass prescription if you have no need for vision correction or if you routinely wear contact lenses to correct your eyesight. Or computer glasses can be specially prescribed to optimize your vision specifically for the distance from which you view your devices.
If you have presbyopia and routinely wear multifocal lenses or bifocals, a prescription computer glasses with single vision lenses will give you the additional benefit of a much larger field of view for seeing your entire computer screen clearly, and is prescribed exclusively for seeing objects within arm’s length and cannot be worn for driving or other distance vision needs. Also, a number of lens manufacturers have introduced special glare-reducing anti-reflective coatings that also block blue light from both natural sunlight and digital devices.
You also may want to consider photochromic lenses, which provide seamless protection from UV and blue light both indoors and out and also automatically darken in response to UV rays outdoors to increase comfort and reduce glare. Ask your eye doctor or optician which type of vision correction and lens features best suit your needs for viewing your computer and other digital devices and protecting your eyes from blue light.
6. Blue light protection may be even more important after cataract surgery.
The lens in the adult human eye blocks nearly 100 percent of the sun’s UV rays. As part of the normal aging process, the eye’s natural lens eventually blocks some short-wavelength blue light as well — the type of blue light most likely to cause damage to the retina and lead to macular degeneration and vision loss. If you have cataracts and are about to have cataract surgery ask your surgeon what type of intraocular lens will be used to replace your cloudy natural lens, and how much blue light protection it provides. After cataract surgery you might benefit from eyeglasses that have lenses with a special blue light filter — especially if you spend long hours in front of a computer screen or using other digital devices.
7. Not all blue light is bad.
Why not block all blue light all the time?
It is well documented that some blue light exposure is essential for good health. Research has shown that high-energy visible light boosts alertness, helps memory and cognitive function and elevates mood. In fact, something called light therapy is used to treat seasonal affective disorder (SAD) — a type of depression that’s related to changes in seasons, with symptoms usually beginning in the fall and continuing through winter.
The light sources for this therapy emit bright white light that contains a significant amount of HEV blue light rays. Also, blue light is very important in regulating circadian rhythm — the body’s natural wakefulness and sleep cycle. Exposure to blue light during daytime hours helps maintain a healthful circadian rhythm. But too much blue light late at night (reading a novel on a tablet computer or e-reader at bedtime, for example) can disrupt this cycle, potentially causing sleepless nights and daytime fatigue.
Blue light filters and protective eyewear
If you are using your phone constantly — especially if you use it primarily for texting, e-mailing and web browsing — a convenient way to reduce your blue light exposure is to use a blue light filter.
These filters are available for smartphones, tablets, and computer screens and prevent significant amounts of blue light emitted from these devices from reaching your eyes without affecting the visibility of the display. Some are made with thin tempered glass that also protects your device’s screen from scratches.
TEN EASY STEPS TO REDUCE EYE STRAIN AND COMPUTER VISION
1. Get a comprehensive eye exam.
Having a routine eye examination every year is the most important thing you can do to prevent or treat computer vision problems. During your exam, be sure to tell your eye doctor how often you use a computer and digital devices at work and at home.
Measure how far your eyes are from your screen when you sit at your computer and bring this measurement to your exam so your eye doctor can test your eyes at that specific working distance.
2. Use proper lighting.
Eye strain often is caused by excessively bright light either from outdoor sunlight coming in through a window or from harsh interior lighting. When you use a computer, your ambient lighting should be about half as bright as that typically found in most offices. Eliminate exterior light by closing drapes, shades or blinds. Reduce interior lighting by using fewer light bulbs or fluorescent tubes, or use lower intensity bulbs and tubes. Also, if possible, position your computer screen so windows are to the side, instead of in front or behind it.
3. Minimize glare.
Glare from light reflecting off walls and finished surfaces, as well as reflections on your computer screen also can cause computer eye strain. Consider installing an anti-glare screen on your display and, if possible, paint bright white walls a darker color with a matte finish.
If you wear glasses, purchase lenses with anti-reflective coating, which reduces glare by minimizing the amount of light reflecting off the front and back surfaces of your eyeglass lenses.
4. Upgrade your display.
If you have not already done so, replace your old tube-style monitor (a cathode ray tube or CRT) with a flat-panel LED (light-emitting diode) screen with an anti-reflective surface. Old-fashioned CRT screens can cause a noticeable “flicker” of images, which is a major cause of computer eye strain. Even if this flicker is imperceptible, it still can contribute to eye strain and fatigue during computer work.
5. Adjust your computer display settings.
Adjusting the display settings of your computer can help reduce eye strain and fatigue. Generally, these adjustments are beneficial:
• Brightness: Adjust the brightness of the display so it is approximately the same as the brightness of your surrounding workstation. As a test, look at the white background of a Web page. If it looks like a light source, it’s too bright. If it seems dull and grey, it may be too dark.
• Text size and contrast: Adjust the text size and contrast for comfort, especially when reading or composing long documents. Usually, black print on a white background is the best combination for comfort.
• Color temperature: This is a technical term used to describe the spectrum of visible light emitted by a color display. Blue light is short-wavelength visible light that is associated with more eye strain than longer wavelength hues, such as orange and red. Reducing the color temperature of your display lowers the amount of blue light emitted by a color display for better long-term viewing comfort.
6. Blink more often.
Blinking is very important when working at a computer; blinking moistens your eyes to prevent dryness and irritation. When staring at a screen, people blink less frequently — only about one-third as often as they normally do — and many blinks performed during computer work are only partial lid closures, according to studies.
Tears coating the eye evaporate more rapidly during long non-blinking phases and this can causes dry eye. Also, the air in many office environments is dry, which can increase how quickly your tears evaporate, placing you at greater risk for dry eye problems. If you experience dry eye symptoms, use artificial tears to rewet your eyes. Do not use eye drops that reduce redness, as they are not necessarily formulated to reduce dryness and irritation.
To reduce your risk of dry eyes during computer use, try this exercise: Every 20 minutes, blink 10 times by closing your eyes as if falling asleep (very slowly). This will help rewet your eyes.
7. Exercise your eyes.
Another cause of computer eye strain is focusing fatigue. To reduce your risk of tiring your eyes by constantly focusing on your screen, look away from your computer at least every 20 minutes and gaze at a distant object (at least 20 feet away) for at least 20 seconds. Some eye doctors call this the “20-20-20 rule.” Looking far away relaxes the focusing muscle inside the eye to reduce fatigue.
8. Take frequent breaks.
To reduce your risk for computer vision syndrome and neck, back and shoulder pain, take frequent screen breaks during your work day (at least one 10-minute break every hour). During these breaks, stand up, move about and stretch your arms, legs, back, neck and shoulders to reduce tension and muscle fatigue.
9. Modify your workstation.
If you need to look back and forth between a printed page and your computer screen, place the written pages on a copy stand adjacent to your screen.
Light the copy stand properly. You may want to use a desk lamp, but make sure it doesn’t shine into your eyes or onto your computer screen.
Poor posture also contributes to computer vision syndrome. Adjust your workstation and chair to the correct height so your feet rest comfortably on the floor.
Position your computer screen so it’s 20 to 24 inches from your eyes. The center of your screen should be about 10 to 15 degrees below your eyes for comfortable positioning of your head and neck.
10. Consider computer glasses.
For the greatest comfort at your computer, you might benefit from having your eye doctor modify your eyeglass prescription to create customized computer glasses.
About the author: Terence Moss is a retired optometrist who has worked in UK, Gibraltar and Australia and is a former Optometry Director of a Specsavers franchise in Melbourne.