Anatomy of the Eye (cont.)
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The vitreous cavity is located behind the lens and in front of the retina. It is filled with a gel-like fluid, called the vitreous humor. The vitreous humor helps maintain the shape of the eye.
The retina acts like the film in a camera to create an image. When focused light strikes the retina, chemical reactions occur within specialized layers of cells. These chemical reactions cause electrical signals, which are transmitted through nerve cells into the optic nerve, which carries these signals to the brain, where the electrical signals are converted into recognizable images. Visual association areas of the brain further process the signals to make them understandable within the correct context.
The retina has two types of cells that initiate these chemical reactions. These cells are termed photoreceptors and the two distinct types of cells are the rods and cones. Rods are more sensitive to light; therefore, they allow one to see in low light situations but do not allow one to see color. Cones, on the other hand, allow people to see color, but require more light.
The macula is located in the central part of the retina and has the highest concentration of cones. It is the area of the retina that is responsible for providing sharp central vision.
The choroid is a layer of tissue that lies between the retina and the sclera. It is mostly made up of blood vessels. The choroid helps to nourish the retina.
The optic nerve, a bundle of over 1 million nerve fibers, is responsible for transmitting nerve signals from the eye to the brain. These nerve signals contain information for processing by the brain. The front surface of the optic nerve, which is visible on the retina, is called the optic disk or optic nerve head.
Six extraocular muscles are attached to each eye to move the eye left and right, up and down, and diagonally, or even around in circles when one wishes.
Medically reviewed by William Baer, MD; Board Certified Ophthalmology
Medically Reviewed by a Doctor on 4/7/2016
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