Eye Strain (Asthenopia)

Eye strain, also known as asthenopia (from Greek asthenopia, ἀσθεν-ωπία, "weak-eye-condition"), is an eye condition that manifests through nonspecific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional double vision. Symptoms often occur after reading, computer work, or other close activities that involve tedious visual tasks.

When concentrating on a visually intense task, such as continuously focusing on a book or computer monitor, the ciliary muscle tightens. This can cause the eyes to get irritated and uncomfortable. Giving the eyes a chance to focus on a distant object at least once an hour usually alleviates the problem.

Symptoms of Eye Strain

Anyone can experience eye strain. It is a fairly common problem in children and adults of all ages. Eye strain produces a number of symptoms. You might feel the effects while you are still reading or looking at a screen. Sometimes, you may not notice these symptoms until after you take a break from what you are doing.

The effects usually last for a few minutes, but they can persist for hours after you finish what you were doing. If you experience frequent eye strain without taking breaks, you can start to develop the symptoms more frequently. And instead of beginning after hours of using your eyes, the symptoms may start right away, as soon as you use your eyes for close vision.

Common symptoms of eye strain include:

Eye soreness

Eye pain

Dry eyes

Squinting

Headaches, especially around your eyes and forehead

Irritability

Fatigue

Sleepiness

Photophobia (light sensitivity)

Dizziness

Blurred vision

Burning eyes

Difficulty reading

Poor concentration

A CRT computer monitor with a low refresh rate (<70Hz) or a CRT television can cause similar problems because the image has a visible flicker. Aging CRTs also often go slightly out of focus, and this can cause eye strain. LCDs do not go out of focus but are also susceptible to flicker if the backlight for the LCD uses PWM for dimming. This causes the backlight to turn on and off for shorter intervals as the display becomes dimmer, creating noticeable flickering which causes eye fatigue.

A page or photograph with the same image twice slightly displaced (from a printing mishap, or a camera moving during the shot) can cause eye strain by 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 (including images deliberately partly blurred for censorship), due to the ciliary muscle tightening trying in vain to focus the blurring out.

Eye strain or eye fatigue can disrupt your ability to use your eyes together. Fatigue in the eyes can also cause reading issues. Eye strain is one of the most common symptoms of an unstable visual system. Eye strain symptoms include; tired eyes, blurry vision, and pain in the eyes.

Causes of Eye Strain

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.

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 a strain which is eventually felt by muscles surrounding the eye (in severe cases, even muscles of the upper cheek and forehead). 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.

Many people who report symptoms of eye strain also have great eyesight in the distance, yet just can't handle the visual stress associated with close work. Visual stress is linked to the development of permanent vision conditions such as shortsightedness, astigmatism and other problems that effect how one lives and behaves.

Diagnosis

If your symptoms are obviously caused by focusing on screens, words, or small objects and then relieved with a few minutes of rest, then you probably have eye strain. You might have a vision deficit, however, and your vision can improve with correction.

If you have other symptoms, such as nausea or severe eye pain, you may need diagnostic tests, which can rule out other problems.

There are several tests your doctor can use to determine whether you have another condition besides eye strain.

Eye exam: An eye exam includes vision testing and involves a detailed examination of the structure of your eyes using non-invasive devices, such as an ophthalmoscope.

Brain imaging: If there is a concern that you could have a structural problem of the brain, you may need to have a brain computerized tomography (CT) or magnetic resonance imaging (MRI) test.

Treatment

There is not a medication or procedure that can relieve eye strain. However, there are a number of useful strategies you can use to manage it.

Methods of managing eye strain include:

Rest your eyes: When you feel eye strain coming on, or even if it is at its worst, just close your eyes for a few seconds. Or give your eyes a break by looking at something that isn't so small or detailed.

Lighting: Use proper lighting when you are reading or working. This can be easy to ignore because you may feel comfortable in the dark—but the effects of eye strain can come on later.

Computer and phone screens: Set your screens so that you have enough contrast to comfortably read, but make sure that the light isn't too bright for your eyes.

Font size: Adjust the font size on your phone or computer. A font that is too small can be hard to see, while large font fills up too much space on the screen, making it cumbersome to read large documents. And be sure to use a clear font without too many hard to read squiggles whenever you can.

Taking breaks: If you have to do tasks that require prolonged reading, or looking at tiny objects, consider looking away every 20 minutes or so. You can close your eyes or look at something far away to give your eye muscles a rest. This shouldn't interfere with your productivity, and it may even help you refocus on the big picture of the project every once in a while.

Correction for vision problems: If eye strain is a major problem for you, it could be due to a vision problem. Be sure to make an appointment to have your eyes and vision checked.

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