Suppression of Aqueous Humor Formation
Various classes of drugs can suppress formation of aqueous humor. The mechanisms of action of these drugs are discussed in Chapter 12.
Inhibition of the enzyme carbonic anhydrase suppresses aqueous humor formation. However, the precise role of carbonic anhydrase has been debated vigorously. Its function may be to provide the bicarbonate ion, which, evidence suggests, is actively secreted in human eyes. Carbonic anhydrase may also provide bicarbonate or hydrogen ions for an intracellular buffering system.
Blockade of β2-receptors, the most prevalent adrenergic receptors in the ciliary epithelium, may reduce aqueous humor formation and affect active secretion by causing a decrease either in the efficiency of Na+,K+-ATPase or in the number of pump sites. For additional discussion of the sodium-potassium pump and the pump–leak mechanism, see BCSC Section 2, Fundamentals and Principles of Ophthalmology. Stimulation of α2-receptors also reduces aqueous humor formation, possibly by means of a decrease in ciliary body blood flow mediated through inhibition of cAMP; the exact mechanism is unclear.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.