Marcus Gunn Pupil

[MudPhud20XX]

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So I am getting confused with diff descriptions about MGP. So one book says you get minimal bilateral constriction when light is shine in the affected pupil whereas the other book says you get a relative dilation of both eyes. What is going on? Also, can anyone just explain these for me? Many thanks in advance.

 

[dfib slim]

If you shine a light in the bad eye first you may get minimal constriction of both eyes.

If you shine in the good eye first both will constrict but when you swing to the other eye the light doesn't register so you get relative dilation.

 

[syma]

So I am getting confused with diff descriptions about MGP. So one book says you get minimal bilateral constriction when light is shine in the affected pupil whereas the other book says you get a relative dilation of both eyes. What is going on? Also, can anyone just explain these for me? Many thanks in advance.

Those mean the same things.

You have a relative afferent pupillary defect.

Assume the right eye is the eye with the problem. With the swinging light test, when you shine the light into the right eye, you will get mild bilateral constriction. Certainly less than you expect

When you shine the light into the left eye you will get bilateral fully expected constriction. And noticeably because it was not fully constricted before.

Swing back to the right eye, and you get what appears to be dilation, swing back to the left eye, you get what appears to be constriction. Rinse and repeat.