What is the Canal of Schlemm?

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  • Written By: Angela Crout-Mitchell
  • Edited By: Jenn Walker
  • Last Modified Date: 03 September 2019
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The Canal of Schlemm is a canal located in the eye, also known as the scleral venous sinus or Schlemm's canal. Circular in shape, the canal's function is to collect fluid called aqueous humor from the anterior chamber of the eye and move it to the blood and vascular system. The aqueous humor is moved via the anterior ciliary veins. Much like a lymphatic vessel, with endothelium lining, the canal also is covered by a mesh-like substance referred to as trabecular meshwork. This sinus received its name from noted German anatomist Friedrich Schlemm.

The aqueous humor plays a major role in the function of the canal of Schlemm as well as in the function of the human eye itself. This substance is produced by secretory epithelium or skin tissue, that lines the ciliary processes and is then released into the posterior chamber of the eye where it helps regulate intraocular pressure between the anterior and posterior portions. The aqueous humor is also present in the anterior portion of the eye, and its job is to mesh with a huge number of collagen fibrils and drain through the duct or canal of Schlemm. The excess aqueous humor fluid is then released into the lymphatic system and allowed to be carried out into the general lymph circulation of the body.


Both Schlemm's canal and the aqueous humor are vital to the health and function of the eye. It is critical for the posterior and anterior portions of the eye to maintain a careful balance of aqueous humor production and drainage to ensure proper pressure of two chambers. The balance of production and drainage also serves to promote the correct spatial distances between the various organelles of the eye. If this important balance is not maintained, it is common for eye disorders relating to distortion of the size and shape of the eyeball to present, and there is an increased potential for seriously impaired vision to occur.

There are two ways in which the canal of Schlemm can be adversely affected, causing dysfunction and possible damage. In addition to eye disease, physical injury to the area can also create an imbalance of the aqueous humor and damage the scleral venous sinus. If too much aqueous humor is produced, the intraocular pressure is likely to rise, causing the potential for serious eye diseases, such as glaucoma. This disease is characterized by optic nerve atrophy, impaired, blurry vision, and eye retina detachment. Left untreated, glaucoma can also result in permanent vision loss.


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Post 3

@MrsPramm - I believe there are also diseases where there isn't enough aqueous humor and the eye can't see properly because of it, but I guess that happens more often when there is an injury to the eye, rather than a disease.

Post 2

@bythewell - I have a grandfather who got glaucoma and ended up completely blind in one eye because he was too stubborn to get it checked out. I wanted to understand what was happening and it makes sense now I know about the canal of schlemm.

Apparently you can get it if you use steroids too much as well, which at least is something I don't have to worry about.

Post 1

Glaucoma is pretty common and is the reason I try to go in for regular eye exams every few years. Once you get past a certain age, you'd be a fool not to go and you're better off doing it if you're vulnerable to glaucoma as well. People with diabetes, for example, often end up with glaucoma.

It's the kind of condition that they can completely fix (or slow down so much it's the same thing) if you catch it early, but once it gets past the point of damage, you can't get that sight back. And people think they'll be able to know when it's happening, but the pressure and damage builds so slowly, you just can't tell.

So, if you are at risk, go and get one of the cheap check-ups that are available almost everywhere. Your sight is worth it.

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