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.