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The optic disc is located 3 to 4 mm to the nasal side of the fovea.It is a vertical oval, with average dimensions of 1.76mm horizontally by 1.92mm vertically. [2] There is a central depression, of variable size, called the optic cup.
An area termed the limbus connects the cornea and sclera. ... The light circle is the optic disc where the optic nerve exits the retina. ... a daily average and short ...
The white cup is a pit with no nerve fibers. As glaucoma advances, the cup enlarges until it occupies most of the disc area. [2] The cup-to-disc ratio compares the diameter of the cup portion of the optic disc with the total diameter of the optic disc. A good analogy to better understand the cup-to-disc ratio is the ratio of a donut hole to a ...
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 in humans is located about 12–15° temporally and 1.5° below the horizontal and is roughly 7.5° high and 5.5° wide. [3]
In megalopapilla the optic disc diameter exceeds 2.1 mm (or surface area more than 2.5 mm 2 [1]) with an increased cup-to-disc ratio. [2] Although the optic disc is looks abnormal, the disc colour, sharpness of disc margin, rim volume, configuration of blood vessels and intraocular pressure will be normal.
Photograph of the retina of the human eye, with overlay diagrams showing the positions and sizes of the macula, fovea, and optic disc. Perifovea is a region in the retina that circumscribes the parafovea and fovea and is a part of the macula lutea. [1] The perifovea is a belt that covers a 10° radius around the fovea and is 1.5 mm wide.
In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus.
On average, each square millimeter (mm) of the fovea contains approximately 147,000 cone cells, [27] or 383 cones per millimeter. The average focal length of the eye, i.e. the distance between the lens and fovea, is 17.1 mm. [ 28 ] From these values, one can calculate the average angle of view of a single sensor (cone cell), which is ...