Schlemm’s canal

After the transport of aqueous humor into the posterior chamber, it flows through the pupil into the anterior chamber where it provides oxygen and nutrition to the avascular lens and cornea. Aqueous humor then exits the anterior chamber through the trabecular meshwork and drains into Schlemm s canal which drains aqueous humor into the episcleral venous system. 

Angle of anterior chamber Schlemm s canal Spaces of fontana Retina... 

The ciliary body, situated posterior to the iris, performs several functions. It connects the anterior part of the choroid to the circumference of the iris, and contains the ciliary muscles necessary for accommodation. The ciliary body secretes aqueous humor into the posterior together with nutrients to nourish the lens. In the ciliary body, melanin is located only in the outer pigmented epithelium [24]. Aqueous humor is actively secreted and passively filtered by the ciliary body. Although the rate of secretion is about 2 pL/min the same volume is drawn-off via Schlemm s canal from where it is conducted into veins [25]. 

The posterior half of the trabecular meshwork and the inner wall of Schlemm s canal also contain adrenergic... 

The cornea serves as the front part of the AC of the eye. Its exterior is covered by the precorneal tear film, which lubricates, nourishes and protects the corneal surface. The iris and the pupil represent the posterior border of the AC. The AC angle is an important sducture which is comprised of Schwalbe s line, Schlemm s canal and trabecular mesh-work, scleral spur, anterior border of the ciliary body and the iris (Figure 5.2). Aqueous humor that fills the AC is produced by the ciliary epithelium located in the posterior chamber. The fluid flows through the pupil and is chained by the habecular meshwork into Schlemm s canal and subsequently into the episcleral vessels. This passage is named the conventional pathway. Aqueous humor is also chained by a uveoscleral pathway across the ciliary body into the supraciliary space. 

Figure 5.2. Drawing of tlie stiuctures of tlie angle of tlie AC and ciliary body. SL, Schwalbe s line SS, scleral spur IP, iris process TM, Ua-becular mashwork C, cornea I, iris SC, Schlemm s canal S, sclera CB, ciliar y body Z, zonular- fibers. (IllusUation from Ocular- Anatomy, Embryology and Teratology 1982, used witli permission from Williams and Wilkins, Philadelphia, PA.)...

Schlemm s canal may be seen if blood reflnxes into the canal. This might indicate elevated episcleral venons pres-snre cansed by conditions snch as a carotid-cavemons fistnla, Graves orbitopathy, or Stnrge-Weber syndrome. 

The aqueous humor flows out the eye mainly via the conventional route of the trabecular meshwork and Schlemm s canal. However, about 10-20% of outflow is via the uveoscleral (nonconventional) route whereby the aqueous humor passes between the ciliary muscle bundles and into the episcleral tissues, where it is reabsorbed into orbital blood vessels and drained via the conjunctival vessels. The IOP-lowering effect of these prostanoid drugs occurs predominantly through enhancement of uveoscleral outflow [26], although unoprostone and bimatoprost also increase flow via the trabecular meshwork to a lesser extent. 

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