Aqueous Production

What does IOP depend on?

aqueous inflow and outflow

Less aqueous production means…

less fluid entering the eye

Reduced volume =

lower IOP (basis for many glaucoma treatments)

Beta-2 receptor activation

Stimulates adenylate cyclase → higher cAMP → lower aqueous humor production

Alpha-2 receptor activation

inhibits adenylate cyclase → lower cAMP → lower aqueous humor production

Adrenergic control of aqueous secretion

Adrenergic receptors in ciliary epithelium

alpha-2 receptors inhibit adenylate cyclase

90% of beta receptors are beta-2; they stimulate adenylate cyclase

Lower IOP (control of aqueous secretion)

stimulates alpha-2 (its agonist is brimonidine)

inhibits beta-2 (beta-blocker is timolol)

Cholinergic (control of aqueous secretion)

little action in ciliary epithelium

Carbonic anhydrase inhibitors (CAI)

Aqueous secretion is decreased by inhibiting bicarbonate formation

Inhibition of carbonic anhydrase reduces bicarbonate production (slows ion and fluid transport across the ciliary epithelium)

Topical and oral CAIs reduce IOP (dorzolamide, brinzolamide, acetazolamide, methazolamide)