Quick Facts
The venous sinus of sclera is a circular channel at the junction of the sclera and cornea, which is the main pathway for elimination of aqueous humor from the eye (Dorland, 2011).
Related parts of the anatomy
Structure and/or Key Feature(s)
The scleral venous sinus, or the canal of Schlemm, is a single-layered endothelial lined canal. These specialized endothelial cells act as a barrier for the drainage of aqueous humor from the anterior chamber of the eye and add resistance to the flow of aqueous humor (Kizhatil et al., 2014).
The anterior wall of the scleral venous sinus is formed from the tough tissue of the sclera. The posterior wall is composed of a triangular mass of trabecular tissue. Aqueous humor drains through the trabecular tissue into the venous sinus.
Anatomical Relations
The scleral venous sinus is embedded within the inner surface of the sclera adjacent to the cornea near the limbus. Additionally, it is located in the tissue of the iridocorneal angle, an angle formed between the iris and the cornea. It is continuous with the small interscleral veins, which connect the canal with the episcleral veins. Although the scleral venous sinus is continuous with the interscleral veins, it usually does not contain blood. Thus, the scleral venous sinus may be considered a lymphatic vessel.
Function
The scleral venous sinus removes aqueous humor from the anterior chamber of the eye. It receives aqueous humor at the iridocorneal angle that filters through the trabecular meshwork. Aqueous humor flows into the bloodstream via the episcleral veins. The scleral venous sinus is responsible for about 70-90% of total aqueous humor drainage from the eye (Truong et al., 2014). Therefore, the scleral venous canal plays an important role in regulating intraocular pressure.
List of Clinical Correlates
—Glaucoma
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Kizhatil, K., Ryan, M., Marchant, J. K., Henrich, S. and John, S. W. (2014) 'Schlemm's canal is a unique vessel with a combination of blood vascular and lymphatic phenotypes that forms by a novel developmental process', PLoS Biol, 12(7), pp. e1001912.
Truong, T. N., Li, H., Hong, Y. K. and Chen, L. (2014) 'Novel characterization and live imaging of Schlemm's canal expressing Prox-1', PLoS One, 9(5), pp. e98245.
