Aqueous humor drainage Flashcards
What is the normal production rate of aqueous humor?
The normal production rate of aqueous humor is 2.0-2.5 µl/min
Describe the conventional pathway for aqueous humor drainage.
The conventional (trabecular) pathway involves the aqueous humor flowing from the anterior chamber through the trabecular meshwork to Schlemm’s canal, then into scleral and conjunctival veins, and finally into the systemic circulation. This pathway accounts for 90% of aqueous humor drainage.
What is the trabecular meshwork and its function in aqueous humor drainage?
The trabecular meshwork is a spongy tissue located around the base of the cornea, near the ciliary body. It acts as a one-way valve, allowing aqueous humor to pass into Schlemm’s canal and then into the bloodstream.
Describe the uveoscleral pathway for aqueous humor drainage.
The uveoscleral (unconventional) pathway involves the aqueous humor diffusing through the intercellular spaces among ciliary muscles, into the suprachoroidal space, and then into the venous circulation of the ciliary body, sclera, and choroid. This pathway accounts for 10% of aqueous humor drainage.
How does the aqueous humor flow from the posterior chamber to the anterior chamber?
Aqueous humor flows from the posterior chamber through the pupil into the anterior chamber, where it then follows the conventional or uveoscleral pathways for drainage.
What factors affect the formation of aqueous humor?
Factors affecting aqueous humor formation include blood flow to the ciliary body, stimulation of the sympathetic nervous system (increased by β2 receptors, decreased by α2 receptors), parasympathetic nervous system (decreased by M3 receptors), and various pharmacological agents such as beta-blockers and CA inhibitors.
What is the pH of aqueous humor in the anterior chamber?
The pH of aqueous humor in the anterior chamber is slightly acidic at 7.2.
Which beta-adrenergic agents are used to increase the production of aqueous humor?
Epinephrine, salbutamol, isoprenaline, and terbutaline
How do beta-adrenergic agents affect aqueous humor production?
Beta-adrenergic agents stimulate the ciliary epithelium, leading to increased production of aqueous humor.
Name a systemic administration that increases aqueous humor production.
Hydrocortisone administration systemically.
What is the effect of intramural epinephrine on aqueous humor?
Intramural epinephrine increases the production of aqueous humor
Which class of drugs is used to decrease the production of aqueous humor by inhibiting carbonic anhydrase?
Carbonic anhydrase inhibitors, such as acetazolamide.
How do beta-blockers like timolol and betaxolol affect aqueous humor production?
Beta-blockers decrease the production of aqueous humor by inhibiting beta-adrenergic receptors in the ciliary epithelium.
Name an alpha-2 agonist that reduces aqueous humor production.
Apraclonidine and brimonidine.
What is the role of ouabain in the regulation of aqueous humor outflow?
Ouabain decreases the production of aqueous humor by inhibiting Na+/K+ ATPase in the ciliary epithelium.
