What is the Fovea Centralis? - Definition & Function

Instructor: Patricia Jankowski

Patricia has a BSChE. She's an experienced registered nurse who has worked in various acute care areas as well as in legal nurse consulting.

The fovea centralis is an area within the retina of the eye located in the center of the macula. This lesson is about the fovea centralis, its definition, and its function within the eye.

Doc, The Lines are Wavy!

''Mr. Doe, now that you're sixty, I want to run some tests on you to check the function of your eyes. I'm going to show you something called an Amsler grid, and I want you to tell me what you see.''

Amsler Grid as Seen By Patient With Macular Degeneration
Amsler Grid

''Doc, the lines are sort of wavy! I don't think they're supposed to be that way!''

''Well, Mr. Doe, you may have some of what is called macular degeneration. I would like to run some more tests if it's okay with you.''

What is the Fovea Centralis?

The fovea centralis is an indented area located on the retina of the eye, in the center of the macula, or macula lutea. Tells you a lot, doesn't it? Don't worry. We're going to define all of this before we're done, but in a nutshell, without a fovea centralis, a person can't see very well at all. That is because the fovea centralis contains cells called cones, which take the light that comes into the eye as an image, and translates it into a nerve impulse that travels to the brain, where it then becomes something that can actually be seen.

Anatomy of the Eye

Let's start by getting a basic understanding of the anatomy of the eye.

The eyeball itself has three layers. The outermost one is the sclera, or white of the eye. This layer is the eye's support structure, and it connects with the cornea, which is the anterior part of the eye, or the part that's in front. The cornea is transparent.

The middle layer is the choroid. This layer has pigments that prevent the light from bouncing around inside the eye, as well as blood vessels. The inner layer of the eye is the retina. This is the layer with nerves that change light waves into nerve impulses that travel to the brain, making vision possible. The amount of light that can get into the eye is controlled by the iris, which is a muscular diaphragm behind the cornea. The iris is located in front of the lens and has an opening in it through which the lens receives light. The lens itself is capable of changing shape to maintain focus of the received image.

The nerve cells that are located in the retina are the rods and cones. Rods are cells that enable us to see in dim light, and they play an important role in night vision. They are very sensitive to light, and it doesn't take much light to activate them. Cones, however, are activated in stronger light, such as daylight. The cones enable most human vision, such as the ability to read, to drive, and to see the fine details of an image. Loss of the cones is much more devastating than impairment of the rods. Losing the rods means night blindness, but losing the cones means total blindness.

Anatomy of the Eye
Anatomy of the Eye

Function of the Macula and Fovea Centralis

The rods of the retina are located on the outer or more peripheral parts of the retina, while the cones are located in and near its center. The macula lutea, or macula for short, is located in the central retina area lateral, or to the side of, the optic nerve, and processes only the light that comes from the center of the visual field. In the center of the macula is the fovea centralis. The macula contains mostly cones and few rods, and the fovea centralis contains only cones and no rods. In the eye disease known as age-related macular degeneration, or AMD, the cones are damaged by a buildup of toxic products of eye metabolism called drusin. Since the cones are needed for central vision, macular degeneration leads to distorted vision, and ultimately, if all the cones are destroyed, to total blindness.

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