What is “Lazy Eye” and How Do I Prevent It?

Many people have heard of a “lazy eye”, but aren’t exactly sure what it is, how to avoid it or how to get rid of it. The medical term for a “lazy eye” is amblyopia, which refers to a person who has reduced vision in one eye that is not associated with eye damage or disease. Amblyopia occurs during childhood and is usually due to either an eye that turns in or out (also known as strabismus), or a person who has a very strong glasses prescription in one eye only. While amblyopia is preventable, it is also the most common visual impairment among children and occurs in ~2% of the population¹. The most significant word of that previous sentence is preventable. So what can you do?

Photo courtesy of mjtmail (tiggy) on Flickr

Photo courtesy of mjtmail (tiggy) on Flickr

The most important thing is for your children to have annual eye exams by an optometrist. How young is too young? Children should definitely have a complete eye exam before entering kindergarten or pre-school to ensure proper vision and eye health for learning. However, kids can be examined at any age, even less than one year, to check for proper focusing, eye movement, and ocular health. Most importantly, see your eye care professional right away if you notice your child’s eye turning either in or out, if they close one eye a lot of the time or if they complain about seeing double images or blurred images. The visual pathways that lead to good vision and eye health over a lifetime are formed primarily by approximately age ten². Therefore, it is important to address any potential problems during that time in order to prevent irreversible vision loss.

One of the most common causes of amblyopia is strabismus or an eye turn. Sometimes it can easily be seen by a parent or teacher, while others are mild and only discovered with testing by an optometrist. Strabismus can also be constant or intermittent; constant is more concerning because that indicates both eyes are not focused on the same image at the same time. Either the child will see double, or two images, or the brain will “turn off” one image in order to avoid this. If one eye is constantly “turned off” to avoid double vision, it will not develop properly and can lead to amblyopia. So what can be done? There are several options depending on the severity of the eye turn. Sometimes the child will grow out of it if the eye turn is mild and or intermittent; the muscles that direct the eyes grow and strengthen just like any other. However, if the problem is more severe or constant, eye exercises or vision therapy can aid that strengthening process to align the eyes. Many optometrists specialize in pediatrics or vision therapy specifically and will develop an individualized plan for each child based on their needs. The most severe cases may need surgery in order to completely straighten the eyes, the need for which can be determined by a thorough eye exam.

More common and also more difficult to detect is anisometropia, where one eye has a very strong glasses prescription compared to the other. In this case, it cannot be seen from the outside like an eye turn, but an optometrist will check for this during an eye exam. If one eye is seeing a much clearer image than the other, again the brain will “turn off” the blurred image and that eye will not develop properly. Sometimes a child may close one eye or obviously favor one eye and that is a clue that they need to be examined right away. So again, what can be done? In this case, the first thing is prescribing glasses. By putting a clear image in front of the eye with the higher prescription, it allows the child to see equally with both eyes, aiding proper visual development and depth perception. Depending on the amount of anisometropia, sometimes the glasses may need to be gradually strengthened over time, as the difference between the two eyes can take time to adapt to the glasses. If vision remains reduced even after full time glasses wear with the full prescription, occlusion of the better seeing eye is recommended. This can be accomplished with either a patch or eye drops to blur the vision of the better seeing eye in an effort to force the poorer seeing eye to process the visual images. This has been shown to work very well to equalize the vision in the two eyes and ensure proper development of both and improve depth perception.

Other rare forms of amblyopia such as blurred vision in one eye from a congenital cataract (the clouding of the lens of the eye from birth) are also possible, which is why a thorough eye exam by an optometrist is so important. All of the above conditions can be treated and improved with early intervention, but can lead to permanent vision loss if left undetected.

~Erin Swift, OD
California Optometric Association

1. Rouse MW, Cooper JS, Colter SA et. al. Care of the patient with amblyopia. St. Louis: American Optometric Association. 2004: 2.
2. https://nei.nih.gov/health/amblyopia/amblyopia_guide

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