physiology of the eye 2 Flashcards
what is aqueous humor?
fluid in the eye
what is the role of aqueous humor?
provides oxygen and metabolites and contain bicarb
bicarb buffers H+ production by the cornea and lens
what is aqueous humor produced by?
energy dependant process in epithelial layer of the eye of ciliary body in post chamber
where does aqueous humor then flow after being produced in post chamber?
anterior chamber
after flowing into anterior chamber where does aqueous humor drain?
scleral venous sinus through trabecular meshwork and canal of schlemm
where is the meshwork and canal of schlemm located?
angle between iris and cornea (iridocorneal angle)
a small amount of aqueous humor diffuses through vitreous being absorbed across what?
retinal pigment epithelium
what are the ciliary body and posterior surface of iris covered by?
2 juxtaposed layers of the epithelial cells
what are the juxtaposed layers of epithelial cells?
forward continuation of pigment epithelium of retina overlain by an inner pigmented epithelial layer
where is HCO3- and H+ formed and from what?
epithelial cells
from hydration of CO2 catalysed by carbonic anhydrase
where are HCO3- and H+ transported across and in exchange for what?
basolateral membranes of pigment epithelium into cells of interstitial fluid
exchange for Cl- and Na+
Cl- and Na+ ions enter cells by diffusing through gap junctions between PE and NPE and are transported out of NPE cells. where are they transported to and via what?
aqueous humor
via Na+/K+/2Cl- cotransporter
what is the movement of Cl- and Na+ through cells from interstitial fluid to aqueous humor followed by?
water moving through ciliary epithelial cell water channels, aquaporins and through paracellular pathway down osmotic gradient
in glaucoma, what is raised intra-ocular pressure caused by?
imbalance between rates of secretion and removal of aqueous humor
what reduces production of aqueous humor?
carbonic anhydrase inhibitors
what are 2 examples of carbonic anhydrase inhibitors?
dorzolamide
acetazolomide
how is dorzolamide administered and why?
eye drops
avoids systemic side effects
how is acetazolomide administered?
orally
