10. Consequences of strabismus Flashcards
What are the consequences and adaptations of strabismus?
- Amblyopia
- Suppression
- Eccentric fixation
- Abnormal retinal correspondence
How were studies on strabismus carried out?
Monocular deprivation studies carried out on animals like monkeys and cats.
They occlude some, surgically induce a strabismus, or use prisms. They carry out these tests on the young animal to check development.
What do the results from the monocular deprivation studies show?
- In the lateral geniculate nucleus there are changes so -lack of laminar structure and -smaller cells
- Main effects seen in the cortex where there is a reduction in binocular cells so dominant eye takes over.
What can we conclude from the monocular deprivation studies?
The development of binocular cells depends on competitive interactions between balanced inputs from the two eyes.
So if unbalanced the dominant eye takes over binocular cells and inhibits inuts from strabismic eye.
What is amblyopia?
Reduction in VA even after refractive error is corrected and there is no pathology in vision.
What are the different types of amblyopia?
- Strabismic (a turn in the eye)
- Anisometropic (A refractive error in one eye)
- Meridional (astigmatism in one eye)
- Ametropic (The two eyes have refractive error)
- Stimulus deprivation (loss of form vision e.g. cataract/ptosis)
How does occlusion therapy help?
- Reduces inhibition from dominant eye
- Increases number of cells driven by amblyopic eye
What is suppression and what are the 2 types?
Inhibition of unwanted stimuli.
Can be physiological or pathological
Physiological -
-unaware of physiological diplopia - unaware of the two images behind or in front of where we are looking.
-Binocular rivalry - the brain can’t fuse the two images from each eye, so eyes will compete for dominance.
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