Topic Overview

The shape of the front part of the eye is maintained by a fluid called aqueous humor.

• Aqueous humor is made by the ciliary body. Strands from the ciliary body support the lens behind the colored part of the eye (iris). See an illustration of the iris and lens.
• Aqueous humor flows into the front of the eye through the pupil.
• Aqueous humor drains out of the eye through the trabecular meshwork. The trabecular meshwork is a spongy mass of tiny canals located in the drainage angle. The drainage angle is located between the iris and the clear covering of the eye (cornea), where the iris meets the white outer covering (sclera) of the eye.
• Aqueous humor is returned into the bloodstream through a tiny channel (Schlemm's canal) located under the trabecular meshwork.

Aqueous humor is produced by and removed from the eye at a constant rate [about 1 tsp (5 mL) per day] to maintain a constant pressure in the front (anterior) chamber of the eye. While pressure in the eye varies throughout the day, the normal pressure within the eye is 10 mm Hg to 21 mm Hg.