Definition for View source for Canal of Schlemm

The aqueous humor plays an important role in the normal functioning of the eye. The balance between its production and drainage is vital to maintaining normal intraocular pressure, and hence normal spatial relationships among the elements comprising the eye's optical apparatus. Too much or too little pressure will cause distortion of the eyeball's shape, and impair vision. 

Aqueous humor is produced by the secretory epithelium covering the ciliary processes; it is released into the posterior chamber, and flows through the pupil to the anterior chamber. There it percolates through the innumerable fine collagen fibrils of the trabecular meshwork (labeled here as TM) in the corneo-iridial angle, and is drained out via a duct running around the eyeball, the canal of Schlemm. The canal is similar to a lymphatic vessel, and the excess aqueous humor is carried through it to the general venous/lymphatic drainage out into the circulation. 

Disease or mechanical trauma can upset this delicate balance. If some condition arises that leads to an excess of production of aqueous humor, or if an injury should cause blockage of the canal, the intraocular pressure may rise dramatically because the normal equilibrium is upset. This leads to glaucoma, which if left untreated can cause blurred vision, detachment of the retina, atrophy of the optic nerve, and permanent blindness.