Visual field defects. Totally confused. Please help!!

[scilearner]

Hello everyone,

 

 

I'm totally confused with this. If there is a lesion in A, why can't you see the left visual field. According to the arrows, if there is a lesion at A, you would not be able to see white areas in pic C. Are they talking about a particular eye or what you see, please either way I don't understand this. What I'm thinking is if there is a lesion at A, when you look at an object you see an object with some areas missing, I'm assuming this is wrong and you can see a whole image in lesion A, but I don't understand. Your help would greatly appreciated. Thanks

Edited January 20, 2011 by scilearner

[ewmon]

Think of the vision fields as what you would see out of your eyes, and follow the cut nerves back to the retina and then to the light flowing into the eye(s).

[scilearner]

Think of the vision fields as what you would see out of your eyes, and follow the cut nerves back to the retina and then to the light flowing into the eye(s).

 

Thanks for the reply but I'm still confused. If I follow the cut nerves in B back to retina, pic doesn't support it. In case A, what do I see. If I close left eye, and look from right eye, is it the same thing I see in case A or do I only see half of an image.

 

What I mean is, this is paris seen from normal eyes

 

 

I don't understand this pic. Why do we see 2 things, don't we see only one thing with our eyes. For me this is like double vision.

 

Paris with bitemporal hemianopia

 

 

In real life what does a person with bitemporal hemianopia see, does he see these 2 images merged together.

Edited January 20, 2011 by scilearner

[SMF]

Scilearner. Your first diagram shows what you would see in each eye separately. A shows that you would not see at all in your left eye, but would see most of the whole visual field, monocularly, but only with the right eye. B is bitemporal hemianopia in your second post. In this you would only see central vision, but binocularly with the two images fused. C shows that you would only be able to see the left visual field, but binocularly.

 

By the way. The photographs you provide shows the two views of both eyes, not overlapped as they would normally be. You can see them binocularly as they would normally appear, with some depth perception, by crossing your eyes carefully until the two fields lock together into a single field. SM

 

 

[ewmon]

Most of the visual fields of our eyes overlap, giving us binocular vision. Only the extreme vision to the sides (ie, "temporal" in the OP diagrams) is monocular, which occurs because of the nose, which blocks the right eye from seeing to the extreme left, and vice versa.

 

The white section of the vision field shown below is the binocular region. The hatched areas on the left and right are the monocular regions of our visual field caused by the nose blocking the opposite eye from seeing. The black areas are not visible with either eye due to the eyebrows and cheeks. So, the visual fields shown in the OP should mostly overlap each other to give a better representation of what one would see.

 

The numbers on the orthogonal axes shown below are degrees. Most people can actually see slightly behind themselves (ie, >90°) out of the outside corner of each eye (but the diagram below only goes out to 90°).