The Eye A Biological Camera

The eye functions much like a camera. Light passes through the cornea and the lens of the eye and is focused on the retina in much the same way that an image is focused on the film of a camera.

The cornea and the lens are transparent and bend light rays in such a way that an image is projected onto the retina. The iris, the colored part of eye, contains the pupil which controls the amount of light entering the eye in much the same way as the shutter of a camera controls the amount of light entering a camera. The light rays then pass through the vitreous cavity that is filled with a clear gelatinous material and are finally focused on the retina. The image on the retina is then transmitted to the brain through the optic nerve. This is the basic mechanism of vision.

The Anterior Chamber

The anterior chamber is a small space between the cornea and the iris. The pupil is the central hole in the iris. The lens is located immediately behind the iris.

It is important to understand the parts of the anterior chamber and their relationship to each other to understand the causes of glaucoma and its treatment. The anterior chamber is filled with a clear fluid that carries oxygen and nutrients to the cornea and lens. Metabolic waste products produced by the lens and cornea are also removed by this fluid.

Fresh fluid called aqueous is constantly produced by an organ called the ciliary body located behind the iris. The fluid then circulates from behind the iris through the pupil, moves through the anterior chamber and finally exits through a drainage mechanism called the trabecular meshwork. The fluid produced by the ciliary body meets some resistance when exiting the anterior chamber through the trabecular meshwork causing pressure to build up inside the eye. The balance between the amount of aqueous production and the ease of drainage through the trabecular meshwork is very important. If the aqueous is produced at higher rate than the rate of drainage the pressure inside the eye will rise. If it rises high enough, damage to the optic nerve will occur with associated loss of visual function.