VisionVision

Vision is much more complicated Vision is much more complicated because these signals have to be because these signals have to be processed into a 3-D imageprocessed into a 3-D image

Fundus Photograph – Hu Fundus Photograph – Hu EyeEye

Fovea

Optic Disk

Blind SpotBlind Spot Find Your “blind spot” Optic DiskFind Your “blind spot” Optic Disk Cover 1 eye with the hand from the same side of your Cover 1 eye with the hand from the same side of your

body, i.e., L hand over L eyebody, i.e., L hand over L eye Fully Extend your free hand with your index finger Fully Extend your free hand with your index finger

pointing upward directly in front of your other eye. Note pointing upward directly in front of your other eye. Note what ever object your index finger is covering and move what ever object your index finger is covering and move your finger just out of the way so you can fix your sight on your finger just out of the way so you can fix your sight on that object.that object.

Now wiggle your index finger while slowly moving it to the Now wiggle your index finger while slowly moving it to the right, left up and down within your peripheral view .right, left up and down within your peripheral view .

Just to the lateral periphery of your fixed view, you will Just to the lateral periphery of your fixed view, you will notice you are “notice you are “blindblind” to your wiggling finger.” to your wiggling finger.

Do the same for your other eye.Do the same for your other eye. Where is your blind spot for your other eye?Where is your blind spot for your other eye? How come you are never aware of your blind spot?How come you are never aware of your blind spot?

Amsler GridAmsler Grid

Amsler Grid

Normal Pre-convergence

Appears Normal to Patient but …..

Crowding, Completion and Fixation “Hide” the Details

Vision Loss

The classic “Kaniza Triangle” – one can clearly see a triangle, even though the borders are composed of virtual

lines formed by the brain

CompletionCompletion

When viewing this face, we automatically scan it with our fovea to form a complete, clear image. The Amsler grid cannot force fixation on a

central point, thereby it cannot prevent the peripheral scanningwhich may mask a non-foveal defect.

This is the actual track of an eye looking at this picture, even though the observer was instructed to stare at a single point on the face

Fixation – Fixation – 1 moment please1 moment please

S R Z+

R+

While staring at the yellow cross in the upper box, try to read the middle letter on the right. Now try to do the same thing

with the lower box. It is easier with the lower box where the “R” stands alone. The neighboring lines in the Amsler Grid reduce the

patient’s ability to isolate and detect visual distortions.

CrowdingCrowding

Can you see which are “popping / pimpling out” of the page and which are “pressing” dimpling / indenting in to the page?

Can you see which are “popping / pimpling out” of the page and which are “pressing” dimpling / indenting in to the page? Does it make a difference in this view?