The small, circular, optically insensitive region in the retina where fibers of the optic nerve emerges from the eyeball. It has no rods or cones.
Every eye has a blind spot where the optic nerve enters the eye and where photoreceptors are absent. We normally do not notice this because the brain fills in the missing information. The brain can give us the illusion of an uninterrupted visual field, but it cannot change the size of the blind spot because the area where photoreceptors are absent is a fixed anatomical feature. Diseases of the retina can cause photoreceptors to malfunction, which may cause an apparent enlargement of the anatomical blind spot or the appearance of additional blind spots at other locations.
The blind spot should always appears in the tests done by VisionField, no matter how healthy are your eyes.
The following picture shows the test results for a healthy left eye and its blind spot is marked as a black box with -1 value.
The blind spot is located about halfway between the center and the periphery of the visual field and has no significant effect on peripheral vision because the same area is visible from the other eye