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Blind spot (vision)
From Wikipedia, the free encyclopedia
A blind spot, also known as a scotoma, is an obscuration of the visual field. A particular blind spot known as the blind spot, or physiological blind spot, is the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the optic nerve passes through it. Since there are no cells to detect light on the optic disc, a part of the field of vision is not perceived. The brain fills in with surrounding detail and with information from the other eye, so the blind spot is not normally perceived.
Although all vertebrates have this blind spot, cephalopod eyes, which are only superficially similar, do not. In them, the optic nerve approaches the receptors from behind, so it does not create a break in the retina.
The first documented observation of the phenomenon was in the 1660s by Edme Mariotte in France, at a time when it was generally thought that the point at which the optic nerve entered the eye should actually be the most sensitive portion of the retina [1].
| Try it yourself | ||||
|---|---|---|---|---|
| A | O | X | ||
| Instructions: Your face should be very close to the screen. Cover right eye and focus the left eye on the X. Now slowly move away from the screen. The O will disappear, while the A which is further to the left is still visible. (Observe that you do not see a hole. Instead of the O you see a uniform grey background. The "hole" is filled in by your brain. Make sure there is not a glare on the screen as it will obscure the whole vision.) |
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Categories: Eye | Vision