One of the most common eye problems is amblyopia, or “lazy eye”, a condition in which one eye doesn’t send signals to the brain as consistently or effectively as the other. Normally light enters the eyes through the corneas and is bent, focused, and “sent” to the back of the eyes where the retinas turn the light into nerve signals. Those signals are full of data – information about peripheral vision, detail and color, to name a few. The impulses travel through the optical nerves to the brain where they are translated into images.
Occasionally though, the brain favors one eye’s signals over those of the other, resulting in an under use of the neglected eye, or “lazy eye.” If untreated, the condition worsens. In adults, amblyopia is the leading cause of monocular visual impairment among adults under 70.
Perfectly aligned eyes can develop amblyopia if their refractive indexes differ substantially. For example, if one eye is quite nearsighted while the other has astigmatism, the brain can cope by relying on just one.
Strabismus, which is a noticeable crossing (or diverging) of the eyes, is usually causal to lazy eye in kids. But many times lazy eye is found independent of strabismus, so even if you don’t notice anything, babies and children should be checked out regularly as they develop. Since the effected eye usually appears normal, the condition can progress undetected to adulthood. Early diagnosis and treatment before the age of 5 or 6 is key to successful outcomes although treatment in the teen years can provide improved vision in the amblyopic eye. If untreated, amblyopia can result in a debilitating lack of vision in one eye, that cannot be corrected with glasses or contact lenses nor treated with surgery.
An eye patch can be employed to correct the condition, but instead of covering the affected eye, your doctor will have the patient’s strong eye patched. This is so that the brain is forced to concentrate its efforts on the amblyopic eye, which is exactly what that eye needs to perform. A couple of hours a day is usually sufficient, but if needed, the patch can be worn up to 6 hours each day.
For children, playing “pirate” can lose its novelty, and some kids may prefer to nix the eye patch. If that’s the case, a drop a day of atropine in the strong eye will produce the same effect. Once applied, the atropine blurs the vision of the favored eye so that the brain relies on the amblyopic eye for its information. Like a muscle being exercised, the affected eye will rise to the occasion and over time, perform up to par. For kids up to 17, treatment is usually effective but the earlier treatment is started the better the result.
Since it tends to produce few symptoms, amblyopia is usually caught at a routine exam. While screenings by a pediatrician or school nurse are beneficial, they should not be substituted for an exam by your primary eye doctor or ophthalmologist.
For questions or comments, contact Woodhams Eye Clinic.