Anatomy of the Eye

Structure of the Eye

An eye is about the size of a ping-pong ball. Light enters the eye through the pupil, and travels through the lens and the vitreous body to the optic nerve. The optic nerve carries the images to the brain for interpretation.

The Chambers

The eye has three chambers known as the anterior (front), the posterior (back), and the vitreous body. The front chamber contains aqueous humor (a watery fluid). This fluid carries nutrients to different tissues in the front of the eye. The cornea is located at the front of this chamber. The cornea is the clear part of the eye.

The iris is the colored part of the eye. The iris is located at the back edge of the anterior (front) chamber. The posterior (back) chamber is the smallest of the three chambers that also contains aqueous humor (a watery fluid).

The lens is located at the front of the posterior (back) chamber and is directly behind the iris. The lens is suspended by ligaments. Behind the lens is the vitreous body, which is the largest chamber of the eye. This chamber contains a thick gel-like fluid called vitreous humor. This fluid helps maintain the shape of the eye.

The Fluid System

The ciliary body located behind the iris produces aqueous humor, which nourishes internal structures and also helps support the shape of the eye. A small area of spongy tissue, called the trabecular meshwork, allows the aqueous humor to drain from the eye. This drainage network is located where the iris and cornea meet, and is called “conventional outflow.” A secondary route for drainage is called “uveoscleral outflow.” When drainage doesn’t keep up with production, the fluid backs up and pressure in the eye increases.

The Dangers of Increased Eye Pressure

Researchers believe increased eye pressure gradually damages the optic nerve, resulting in slow, progressive loss of vision. Most people have no pain or obvious sign of a problem, although the damage continues. Being unaware of the problem is the real danger. Although the cause of the increased eye pressure associated with glaucoma is unknown, studies suggest that lowering the pressure helps slow the risk of further progression of the disease.

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