Expanding the Model-Input

Returning to our model of how the visual system works, Input is the first piece and evaluating input involves determining how well the eye itself functions.  Input can be broken down even further if we specific questions about how the eyes functions.  Standard eye care asks two questions, is it healthy and can it see?  Developmental optometry goes on to examine tracking, focusing and eye coordination.

Are they healthy? In other words are there any disease processes which are affecting the eyes?

There are many diseases which can affect the eyes, thankfully they are rare in children but they do occur.  Possible diseases include:

• Cataracts

• Diabetes

• Retinopathy of Prematurely

• Cancer
   

Can they see?

This is really a question how well can each eye see individually?  If we know each sees well individually then we can be relatively sure we can get them to see well everywhere.  Things we might find here include:

• Amblyopia

• Refractive error

• Myopia (nearsightedness)

• Hyperopia (farsightedness)

• Astigmatism
   

How well do they work together (tracking and eye coordination)?

Can they work together to see a single image?  Is it in 3-D?  Are the eyes straining to line up or do they work efficiently? Is one image significantly larger than the other?  Concerns here include:

• Strabismus (eye turns)

• Convergence insufficiency

• Convergence excess

• Saccade and pursuit dysfunctions (tracking problems)
   

Does the focusing system work?

The focusing system allows us to shift our focus from one distance to another.  Do both of them work?  Can they shift focus efficienctly? Can they maintain focus without fatiguing? Disorders here include:

• Accomadative infacility

• Accomodative insufficiency

• Accomodative excess
   

All these areas are related, so even a small problem can reverberate throughout the entire visual system causing problems including eyestrain, headache, and poor reading skills.

“Dodge”

William Dodge Perry, OD