Aqueous Humor Pathway: Glaucoma
Timolol, betaxolol, carteolol
-Dec. aqueous humor secretion Side effects: No pupillary or vision changes
Acetazolamide
-Dec. aqueous humor secretion d.t. dec. HCO3- (via inhibition of carbonic anhydrase Side effects: No pupillary or vision changes
Brimonidine
-Dec. aqueous humor synthesis Side effects: No pupillary or vision changes
Epinephrine
-Dec. aqueous humor synthesis d.t. vasocontriction Side effects: -Mydriasis, stinging -DO NOT USE IN CLOSED-ANGLE GLAUCOMA
Aqueous humor pathway
-Formed in the capillary bed in the ciliary body -Secreted into the posterior chamber -Transported into ant. chamber via pupil -Flows into angle formed by the lens in the iris diaphragm -Posterior chamber—>lens/iris—>ant chamber -Once in Ant. chamber reabsorbed by the Canal of Schlemm -If this pathway is interrupted or if aq. humor over produced cx glaucoma
-Direct (pilocarpine, carbachol) -Indirect (physostigmine, echothiophate)
-Inc. outflow of aqueous humor;contract ciliary muscle and open trabecular meshwork; use pilocarpine in emergencies; very effective at opening meshwork into canal of Schlemm Side effect: -Miosis -Cyclospasm (contraction of ciliary muscle of the eye)
Latanoprost (PGF-2a)
-Increase outflow of aqueous humor Side effects: -Darkens color of iris (browning), inc. eyelash growth
Closed/narrow angle
-Obstruction of flow is between the iris and cornea. Pressure buildup behind iris -Usually happens when the pupil is dilated and the is stuck to the back of the iris. This prevents the aqueous humor from flowing from the pupil into the ant. chamber. Accumulation of fluid in the post. chamber presses on the iris causing it to bulge outward and block drainage into the canal completely. MEDICAL EMERGENCY! Sx: -Very painful -Rock hard eye -Frontal headache -Pupil not reactive to light (fixed in mid-dilation) -Colored halos and rainbows around light -DO NOT GIVE EPINEPHRINE or Atropine causes mydriasis and makes it worse At risk: Narrow drainage angle, shallow ant. chamber, thin and droopy iris
Open/wide angle glaucoma
-The path of aqueous flow is open but the rate at which aqueous humor is absorbed by the canal of Schlemm or trabecular network is slow. Sx: -Silent/painless -Insidious onset -Almost always bilateral ->40 -DM -African American -LOSS OF PERIPHERAL VISION
*Glaucoma*
A group of eye diseases in which the optic nerve is damaged leading to irreversible loss of vision. In most cases damage is due to an increased pressure with in the eye. -Drainage of aqueous humor is either partially or fully blocked, fluid builds up in the chambers causing a back pressure driving the lens and vitreous body back. The back pressure damages the blood vessels and nerves running at the back of the eye leading to patches of vision loss.
