Why is optic disc called blind spot

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Namespaces Home Page Discussion. Surprisingly, we are normally unaware of these natural blind spots. They are either filled in perceptually a remarkable phenomenon or they are ignored and so not seen.

The blind spot can be demonstrated very simply on paper with a fixation point and for example a letter such as an X, separated horizontally. Fixate the O with only the right eye open, and move your head slowly nearer and further until at a certain distance about 25 cm the X will disappear, when it falls on the blind spot of the open right eye.

As we have said, there are two hypotheses concerning the invisibility of scotomas. Either they may be filled in by brain activity, or simply ignored. These two ideas have very different implications: creating implies active brain processes of memory and imagination affecting vision, ignoring is simply rejecting what is there or what is signalled.

The American philosopher Daniel C. Dennett Dennett, has suggested passive ignoring as important, including for thinking about consciousness.

However there is physiological evidence Komatsu et al, for active creation of perceptual phenomena in the absence of stimuli, suggesting there is more than ignoring. The creative hypothesis is the active filling-in of blind regions by surrounding objects or patterns, including their colours, which are seen though there are no signals from this region of the eye.

Filling-in is more easily seen over small areas. The optic disk is the part of the retina where the optic nerve leaves the eye and heads to the brain. In the optic disk, there are no receptor cells. Axons of the retinal ganglion cells gather at the optic disk and form the optic nerve, which carries the neural signal into the brain. Because there are no receptors at the site of the optic disk, this location is also called the blind spot.

Because the blind spot on the left eye does not correspond to the same region in space as the blind spot on the right eye, humans really do not have a blind spot in their visual field. Even when viewing the world with only one eye, we are not aware of our blind spot. Institutional subscriptions support Language. Keep me signed in. Forgot your password? Sign in with Facebook. Sign in with Apple. Description About 3 mm. This definition incorporates text from the wikipedia website - Wikipedia: The free encyclopedia.

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