Question

in a detailed paragraph what is the fovea and how does it differ from the rest of the retina?

Answer 1

In a detailed paragraph what is the fovea and how does it differ from the rest of the retina?

The retina is the nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which translates that image into electrical neural impulses to the brain to create visual perception.

Anatomy Of Eye - The human retina is located on the inner surface of the posterior two-thirds to three-quarters of the eye. The eye itself is a mostly hollow organ, roughly spherical in shape. In adults, the eye measures approximately 22 mm in diameter. The walls of the eye consist of the firm outermost coat, comprised of the white sclera in the posterior three-quarters of the eye and the clear cornea in the anterior one-quarter of the eye. The middle layer consists of the Uveal tract made up of the choroid posteriorly and the ciliary body and Iris anteriorly. The retina is the innermost layer. It lines the entire posterior portion of the eye with the exception of the area of the optic nerve and extends anteriorly to end 360 degrees circumferentially at the ora. The total area of the retina is approximately 1,100 mm2 ­­. The circumferential diameter at the equator of the adult eye averages 69 mm. The retinal distance circumferentially passing posteriorly from a point on the Ora Serrata to a point on the Ora Serrata 180 degrees away is approximately 50 mm. The average healthy retina is 250-µm thick immediately adjacent to the temporal margin of the optic nerve.

The Fovea

Fovea: In the eye, a tiny pit located in the macula of the retina that provides the clearest vision of all. Only in the fovea are the layers of the retina spread aside to let light fall directly on the cones, the cells that give the sharpest image. Also called the central fovea or fovea centralis. It lies in the middle of the macula area of the retina to the temporal side of the optic nerve head. It is an area where cone photoreceptors are concentrated at maximum density, with exclusion of the rods, and arranged at their most efficient packing density which is in a hexagonal mosaic. Within the fovea is a region of 0.5mm diameter called the foveal avascular zone (an area without any blood vessels). This allows the light to be sensed without any dispersion or loss.

The centre of the fovea is known as the foveal pit and is a highly specialized region of the retina different again from central and peripheral retina. Below this central 200 micron diameter central foveal pit, the other layers of the retina are displaced concentrically leaving only the thinnest sheet of retina consisting of the cone cells and some of their cell bodies which is called the fovial slope. At the edges of the foveal slope rim of the fovea is made up of the displaced second- and third-order neurons related to the central cones. Here the ganglion cells are piled into six layers so making this area, called the foveal rim or Para fovea. The whole foveal area including foveal pit, foveal slope, Para fovea and perifovea is a yellow pigmentation to the macular area known as the macula lutea. As mentioned earlier the concentration of cone cells are of highest number in fovea hence it is responsible for day vision while the retinal periphery is responsible for night vision due to the presence of Rods