Eye strain, also known as asthenopia, is an eye condition that manifests through non-specific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional double vision. Symptoms often occur after long-term use of computers, digital devices, reading, driving long distances or other activities that involve extended visual tasks. When concentrating on a visually intense task, such as continuously focusing on a book or computer monitor, the ciliary muscles and the extraocular muscles are strained. This causes discomfort, soreness or pain on the eyeballs. Closing the eyes for ten minutes and relaxing the muscles of the face and neck at least once an hour usually alleviates the problem. It is more important to ensure seven to eight hours of uninterrupted sleep every night to allow the tissues to heal. A CRT computer monitor with a low refresh rate or a CRT television can cause similar problems because the image has a visible flicker. Even if this flicker is imperceptible, it can still contribute to eye strain and fatigue. Aging CRTs also often go slightly out of focus, and this can cause eye strain. Old tube-style monitors can be replaced with a flat-panel LCD like those on laptop computers. LCD screens are easier on the eyes and usually have an anti-reflective surface. A page or photograph with the same image twice, but slightly displaced can cause eye strain due to the brain misinterpreting the image fault as diplopia and trying in vain to adjust the sideways movements of the two eyeballs to fuse the two images into one. Eye strain can also happen when viewing a blurred image, due to the ciliary muscle tightening trying in vain to focus the blurring out. Subtle blurring is also induced by the poor refractive properties of plastic and polycarbonate lenses. Glass lenses are known to offer better visual acuity.
Sometimes asthenopia can be due to specific visual problems—for example, uncorrected refraction errors or binocular vision problems such as accommodative insufficiency or heterophoria. It is often caused by forcing the eye to focus and interpret visual data on a small region for a prolonged period of time. This can be caused while reading a book, driving a vehicle, using a digital screen or any similar task which fatigue the eye muscles. The condition worsens due to the buildup of fatigue over an extended period of time. The buildup of eye strain happens as a result of obtaining only four to six hours of sleep every night. This cause often goes unnoticed due to sleep state misinterpretation. While there are many causes for middle of the night insomnia, it can also be caused by something as simple as consuming rice that has not been fully cooked or has been cooked with insufficient water. Sleep loss caused by such direct and indirect phenomena are the primary reason that eye strain builds up over a period of years, weakens vision and results in pain. Eye strain can also be a result of the distortion caused by the refractive properties of certain types of spectacle lenses. The subtle blurriness caused by this distortion in peripheral vision, requires eye muscles to strain in order to retain clear vision. Such prolonged distortion can lead to an increase in strain which is eventually felt by muscles surrounding the eye. Plastic lenses cause greater distortion than glass lenses and this can easily be verified by focusing both eyes on a screen directly in front and turning the head left or right while continuing to look at the same spot on the screen while wearing spectacles. Frequent changes in spectacle lenses results in the focal point of the new spectacles being different from the older spectacles. This forces the eye muscles to re-adjust and causes more strain. This adjustment becomes more difficult after the age of 26.
Prevention
Many myths and incorrect advice are propagated about eye strain caused as a result of fatigue to the extraocular or intraocular muscles. The primary cause of strain is the lifestyle adopted or forced upon people, where the eyes are subjected to prolonged periods of strain and not allowed sufficient uninterrupted sleep time to aid recovery. Needing spectacles is not normal. It shows that the eyes have been severely affected for many years from lack of rest, sleep-loss and/or poor nutrition. It's an emergency that needs immediate attention and corrective measures to give the eyes rest and nutrition. Alleviating eye strain:
Obtain at least 8 hours of uninterrupted sleep each night. Good sleep is the most effective eye strain cure.
Adjust the lighting: When watching television, keep the room softly-lit. When reading printed materials or doing close work, position the light source behind you and direct the light onto your page or task. Reduce monitor brightness to a comfortable level.
Take breaks hourly: Rest your eyes by closing your eyes and relaxing your face muscles and neck muscles. Strain builds up primarily due to intraocular and extraocular muscles not being rested. Closing the eyes is the only way to rest them.
Improve the air quality of your space: Some changes that may help prevent dry eyes include using a humidifier, adjusting the thermostat to reduce blowing air and avoiding smoke.
Anti-glare lenses can reduce strain very slightly.
