Optic Disc
The optic disc is the round yellowish area of the retina where the blood vessels enter and exit and neurons leave on their way to the brain. Since there are no photoreceptors at the optic disc, there is a phsyiological blind spot that occurs. Click here to view a chart that will demonstrate the blind spot. Close your left eye. Position your right eye directly in front of the plus sign. Move in to about one foot in front of the screen while staring at the plus sign. You will notice that the circle to the right disappears! This happens because the image of the circle at that position is falling upon the optic disc. There are no rods or cones to pick up this image, so it appears as if nothing is there.
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