Is the Amblyopic Eye Learning Disabled?

It’s good to remind ourselves when dealing with people in VT that it isn’t just eyes we’re considering, but how an individual uses his eyes to function visually.  I’m going to take the liberty of referring to eyes, but as you read through this keep in mind we’re referring to visual processing through the right eye as related to visual processing through the left eye, and how they complement one another to provide optimal performance.  This reinforces the material by Drs. Fortenbacher, Stull, and Tran that amblyopia is best conceptualized and treated as a binoculoar vision problem that involves perceptual learning.

There are two very important principles that we can use to answer the question posed as to whether the amblyopic eye is learning disabled:  1) Developmental Disabilities, and 2) Perceptual Learning.  One of the best sources around on appreciating the deeper implications of amblyopia is the textbook on the subject co-authored by Ciuffreda, Levi, and Selenow.  Define amblyopia.  Go ahead – think about it for a few moments.  Just about every definition you’ll find has something to do with visual acuity.  It might be “A difference in best corrected acuity between the two eyes”.  Or perhaps “Acuity reduced to BVA worse than 20/20 in one or both eyes”.  Nope.  As spelled out very clearly by these three authors, amblyopia is a developmental disorder of spatial vision.  The challenge is to tip the sacred cow of visual acuity in amblyopia.

In an essay in the Journal of Behavioral Optometry I wrote about the change overdue in tipping the sacred cow that defines amblyopia only in terms of visual acuity.  Yet even if we maintain the surface definition of amblyopia in terms of visual acuity, there should be a hint about what resides beneath the surface in terms of visual crowding – a crucial set of features in visual performance.  What differentiates amblyopia from every other visual function we consider as clinicians is that we can compare visual performance through one eye or channel with performance through the other eye.  The patient therefore serves as his own control, and when performance with one eye is significantly poorer than the other eye there has to be an explanation.  Equally if not more important, amblyopia  compromises the binocular integrity of the patient resulting in poorer overall visual performance.

 

In a symposium presentation at the upcoming Vision Sciences Society meeting, Dr. Dennis Levi, co-author of the textbook on Amblyopia will note that visual crowding represents an essential bottleneck, setting limits on object perception, eye movements, visual search, reading and perhaps other functions in peripheral, amblyopic and developing vision.

So does all mean that we can definitely state that the amblyopic eye is learning disabled?  Stay tuned for Part 2.