Gadgets and Eyesight - Good Read

Watching those screens close-up may not permanently damage your eyes, but, it surely can put undue stress on the eyes and leave them feeling strained and fatigued. People who spend two or more continuous hours in front of the screen are at a greater risk of developing a temporary condition called digital eye strain or computer vision syndrome (CVS). Some of the common symptoms are eyestrain, headaches, blurred vision, dry eyes and pain around the neck-shoulder region which usually disappears after one ceases to use the device.

Images in the electronic devices like computer are created from thousands of tiny dots. Unlike the high contrast of printed matter, there is no distinct image in those electronic devices for your eye to actually focus on. Your eyes strain to focus and refocus to keep the images sharp.
The presence of glare and reflections on the screen from the lighting can make viewing difficult. Different distances and angles also result in aggravating the issue. The constant readjustments of your eyes to accommodate all these factors cause you to open your eyes wider. This can lead to your eyes getting dry.

Blinking is an essential component to keeping our eyes healthy. When looking at a screen you blink two-third times less than usual. Less of blinking strains and dries your eyes.
Ideally, the screen should be at eye level or the top of the screen should be at 17 degrees above the eye level. Laptops disturb the eye level. This naturally forces you to stare at the screen and blink lesser number of times, causing eye strain and headache.
Staring at the computer screen or television for prolonged periods can stress the eye muscles to a great extent and trigger twitching.
Old tube-style monitor (called a cathode ray tube or CRT) screens can cause a noticeable ‘flicker’ of images and strain the eye. They can emit a small amount of X-ray radiation which is widely considered not harmful.
Newer display technologies are liquid crystal display (LCD), plasma display, and OLED. To produce a visible image, most LCDs are illuminated from the front or back of the display panel. Older LCDs have CCFL backlit monitor. The newer LED backlit monitors use pulse width modulation (PWM) to alter their brightness. Most of the computer monitors, mobile phones, tablets and television screens have them. PWM can cause distracting visual effects. And according to a research [1], prolonged and continuous exposure to short-wave, high-energy visible light in violet/blue end of the visible light spectrum of LED lights can cause irreparable damage to the retina of the eye.

What factors can increase the risk?
1. Distance and angle
Sitting very close to the screen can strain the eyes. The viewing distance for a TV should be the distance from where you don’t have to squint to read the text on the screen. The eyes have to work harder to look at something at a short distance. Also, watching TV while lying down can strain your eyes. Optimally, the computer screen should be 15 to 20 degrees below eye level (about 4 or 5 inches) as measured from the centre of the screen and 20 to 28 inches from the eyes.
2. Lighting
The pupils dilate to regulate the amount of light that enters the eyes. The degree of dilation is dependent on average lighting of the vision field. Watching TV or working on a computer in a dim lit room can force the pupils to unnecessarily strain to adjust dilation. This can cause the eyes to be fatigued. Bright light from the screen can strain the eyes and you could develop dry eyes.
3. Inappropriate eyeglass or contact lens
Reading glasses correct near vision only, and bifocals correct only near and far. They do not correct the intermediate zone at all. So people who have an eyeglass or contact lens prescription may find it’s not suitable for the specific viewing distances of their computer screen. Without appropriate eyeglasses, computer users end up with blurred vision, eyestrain and, often, headaches.

What measures can you take to prevent eye strain and fatigue?
1. Avoid watching TV in a dark room for extended periods of time. But if you prefer watching TV in the dark, an ambient backlight (light behind the TV) can help reduce eyestrain.
3. Adjust brightness of your screen to reduce reflection.
4. Upgrade your display. Replace your old tube-style monitor (called a cathode ray tube or CRT) with a flat-panel liquid crystal display (LCD).
5. The newer LED backlit monitors use pulse width modulation (PWM). If PWM bothers your eyes, try adjusting the brightness. If it doesn’t provide relief you can switch to older LCDs that have CCFL backlit monitor.
6. While working on a computer adjust the location of computer screen. Place the screen within 20′-24′ of your eyes and at a comfortable angle (15 to 20 degrees below eye-level as measured from the centre of the screen).
7. Wear zero power (if you don’t have corrective glasses) anti-glare glasses or use an anti-glare screen. Appropriate eyeglasses are necessary to prevent eyestrain. This is especially important if you wear bifocals or progressive lenses.
8. Blinking constantly helps too. It moistens your eyes to prevent dryness and irritation. Use artificial tears if you have dry eyes.
9. Take frequent breaks – a 15 minute break for every two hours of computer use.
10. Use the ’20-20-20 rule’ to reduce your risk of tiring your eyes while constantly focusing on your screen. Look away from your computer at least every 20 minutes and gaze at a distant object 20 feet away for at least 20 seconds. Looking far away relaxes the focusing muscle inside the eye to reduce fatigue.
11. Position your computer so that any windows are to the side of the monitor, rather in front or in back to prevent glare and reflection on your monitor. Use a glare filter to reduce the amount of light that can reach your screen.
12. Adjust your computer’s brightness to same as the surroundings and adjust the text size and contrast so that it is comfortable to read. Black print on a white background is the best combination for comfort.
13. Reduce the amount of blue colours on your screen. Blue light is short-wavelength visible light that is associated with more eye strain than longer-wavelength hues, such as orange and red.
14. Use e-readers to read digital e-books. They mimic the appearance of ordinary ink on paper with the help of electronic ink display technology. They are more comfortable to read because the image is displayed on a matte screen in grey scale.
They reflect light like paper unlike light-emitting backlit LCD displays.

Point to remember
Sitting close to the TV may not make one near-sighted. But chances are that an undiagnosed near-sightedness is making one, especially a child, sit closer to the television! If that is the case, it is important to get your eyes tested soon. more  

Besides single vision and bifocal products there are progressive power glasses that take care of vision needs at all distances...and there is also no dividing line between the distance and near powers, that gives out the fact that you are a presbyopic (over-40) - Dr Narendra Kumar, Ophthacare Eye Centre more  
Really a very useful write-up.Thanks more  
Thanks Mrs.Verma for highly useful tips for the best viewing of TVs/PCs/laptops. more  
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