NBME3 spoiler vision question

[Phloston]

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Choice C is correct.

Can someone please explain the difference between choices C and E?

Why is it not choice E?

Thanks,

 

[withrye]

Separate representations of each retina would only happen if the optic nerve fibers did not decussate at the chiasm. With strabismus, the representations from each retina are successfully made in the cortex, because all the cells and fibers are intact. The problem is the eventual correction for the mismatch in representation, which is to ignore the information coming from one eye. This is different than saying that the separate representations never happened to begin with. C, on the other hand, is simply true without qualifications. There isn't any normal binocular vision developed while the eyes are offset.

 

[Belleza156]

I dont know about surgical correction, but I know kids will have to wear an eye patch over their normal eye so that they don't develop a "lazy eye". Also my friend's daughter had to wear eyeglasses since age 3 to correct for the strabismus, same reasoning.

 

[Kaputt]

Seems like this is more of a Step 2 concept. Strabismus causes amblyopia, where basically the brain shuts down input from one eye since it's getting conflicting information from the eyes. Surgical correction prevents this.

 

[Dallas]

Because C is a more well formulated answer. E seems like a "cant see the forest for all the trees" kinda answer.

 

[HelpPleaseMD]

Because C is a more well formulated answer. E seems like a "cant see the forest for all the trees" kinda answer.

agreed. lol

 

[JRjcu08]

Choice C is correct.

Can someone please explain the difference between choices C and E?

Why is it not choice E?

Thanks,

There are two types of amblyopia that produce visual defects in kids. Strabismus produces amblyopia because the "bad" (misaligned) eye is not seeing in stereo with the "good" (straight) eye. The result is failure to have binocular vision, because each eye sees well on its own, but they do not produce an image in stereo. This type of amblyopia occurs less frequently because it is easy to spot a kid with a crooked eye. Treatment is to patch the good eye to force the bad eye to straighten out, or surgery if this is unsuccessful.

The other type of amblyopia is due to anisometropia, or unequal refractive error in the "bad" eye compared to the "good" eye. This often goes unnoticed if a kid "cheats" on his/her vision screening, which is why it is super important to check vision in a young child and make sure the eye not being tested is complete covered. This scenario results in separate representations of the retina developing on the visual cortex because the "bad" eye does not produce a clear image while the "good" eye does. If this is not corrected in childhood the visual cortex that the "bad" eye/retina projects to will be unable to process images. (This type of amplyopia also occurs in scenarios that cause blockage in the eye, such as infantile cataracts that are uncorrected, or some other injury/damage that blocks projection to that eye). Treatment involves correcting the refractive error (or blockage) in the bad eye.

 

[Phloston]

Thanks for the input, guys.