Most people refer to amblyopia as “lazy eye”, which isn’t a very good term for it because the problem is with the brain more so than the eye. Amblyopia is the inability to see 20/20 that can’t be attributed to needing glasses, or to eye disease.
There are two primary causes of amblyopia:
- A difference in power between the two eyes, where one eye is much more nearsighted or farsighted than the other eye
- A constant strabismus or eye turn
From the brain’s standpoint, it doesn’t make much sense to work that much harder to see with the eye that requires more effort. That’s where the idea of “lazy” comes in to play. But it’s really an adaptation that the brain makes to reduce confusion about which eye it is using to provide us with sharper eyesight.
There are however many more things different about how the brain sees with one eye compared to the other eye in amblyopia. These include focusing, tracking, visual crowding, and a variety of visual processing or perceptual problems. This is why merely patching the preferred eye, and letting a child go about her or his daily activities, isn’t a very good way of treating amblyopia to get a lasting result.
Another misconception about amblyopia is that there is some sort of critical period after which a child is too old to benefit from amblyopia therapy. Evidence-based medicine has now shown that it is possible to treat amblyopia at an older age, thanks in large measure to appreciating the role of neuroplasticity. Susan R. Barry, Ph.D., is a neurobiologist who has called significant attention to the idea that the benefits of vision therapy should not be withheld from the public. She writes an excellent blog called Eyes on the Brain, which can be viewed in Psychology Today’s Blog.