A blind sport, scotoma, is an obscuration of the visual field.
A particular blind spot known as the physiological blind spot,
"blind point", or punctum caecum in medical literature,
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 the optic disc.
Because there are no cells to detect light on the optic disc,
the corresponding part of the field of vision is invisible.
Processes in the brain interpolate the blind spot based on
surrounding detail and information from the other eye,
so it 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 the time 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;
however, Mariotte's discovery disproved this theory.
The blind spot is located about 12-15°temporally and 1.5°
below the horizontal and is roughly 7.5°high and 5.5°wide.