Amblyopia (lazy eye)

Amblyopia is an early childhood condition in which one or (rarely) both eyes do not develop the normal capacity to see.

It is one of the most common causes of irreversible visual impairment, affecting up to 2% of the population.

The impairment can be mild to moderate, ranging from a relatively good 20/30 to a legally blind 20/200.

Because amblyopia affects the brain's visual center, which develops within the first 5-6 years of life, it must be treated in early childhood. After the age of 5 or 6, the condition becomes permanent.

A lazy eye can be caused by a few factors including: 

• Refractive error: The eye may be very nearsighted, farsighted, or have a lot of astigmatism. In these cases of refractive amblyopia, the images are so blurry that the brain never sees a normally focused image coming from the affected eye. 
• Eye disease: Another disease, such as a cataract, obstructs light that normally enters the eye causing obstructive amblyopia. Or, in the case of a disease like optic nerve hypoplasia that damages the eye and vision, the damage is compounded by amblyopia. 
• Strabismus: The eyes may be crossed, otherwise known as strabismus. This situation may lead to strabismic amblyopia. 

Amblyopia is very treatable if caught early. The treatment for amblyopia depends upon the cause: 

• Refractive amblyopia from astigmatism, farsightedness, or nearsightedness can be treated by glasses and patching. 
• Obstructive amblyopia (such as from a cataract) can only be treated if the obstruction is first cleared (e.g., cataract removal). Then, any refractive error must be treated and patching performed to force the eye to be used. 
• Patching treats strabismic amblyopia as well as amblyopia from other diseases, such as optic nerve or retinal dysfunction. 

Patching involves placing a patch over the strong eye to force the weaker eye to be used. The use of a patch should be carefully prescribed and monitored by an ophthalmologist.

There are several potential complications with using a patch. The most common problem is that patching does not improve vision in the amblyopic eye. In some cases, patching can result in a reversal of the amblyopia - the previously good eye becomes impaired while the treated eye improves. Lastly, some children may develop strabismus after patching. In general, however, treating the amblyopia is still the more important consideration.

In some cases, eye drops can be used in place of a patch to blur the "good" eye.