Metabolic profile of the eye Flashcards
function of the cornea
ion transport, energy production and an antioxidant system
where does mitosis occur in the corneal epitheium
basal epithelial cells
what is the critical component in the composition of the cornea ?
water (78% of the composition of the cornea)
what counter-acts the uptake of water into the cornea ?
active transport of bicarbonate out into aqueous humor
the aqueous humor is
hypertonic with respect to the cornea and maintains corneal transparency
prolonged wearing of contacts causes hypoxia which results in
increased lactate production, decreased corneal pH and corneal swelling
(t/f) the cornea has the HIGHEST rate of flux through the PPP of any tissue (this supports the anti-oxidant system)
True
aqueous humor is secreted by
ciliary processes into the posterior chamber
where does the aqueous humor drain into
the canal of schlemm
function of aqueous humor
brings nutrients to the cornea and the lens and removes metabolic end products from the cornea and the lens
increased intraocular pressure results in ?
glaucoma and damage to the optic nerve
what causes primary open angle glaucoma
blockage of the drainage canal
what causes angle closure glaucoma (narrow angle glaucoma)
outer edge of the iris blocks entrance to canals there are both chronic and acute forms
what causes normal tension glaucoma
optic nerve damage depite normal IOP
function of the vitreous humor
support function, metabolic carrier for the retina fibrillar network of proteoglycans
holds the proteoglycan bridges apart maintaining sparse meshwork
hyaluronic acid
symptoms include flashing lights or floaters
posterior vitreous detachment (PVD)
PVD is due to
shrinkage and collapse of the vitreous
what are to high content molecules in the lens ?
glutathione and cholesterol
________is crucial to lens transparency
water
energy production in the lens is mainly
anaerobic glycolysis
sorbital pathway is important in
lens (metabolizes high glucose and reduces NADPH levels)
10% of glucose metabolism in the lens is via
HMP shunt
at high glucose concentrations, glucose is converted to
sorbitol
the conversion of glucose to sorbitol depletes
NADPH
loss of transparency of the lens and aggregation of proteins is charactertici of
cataract formation
mechanism of cataract formation
osmotic uptake of water causes crystallins to aggregate increasing light-scattering
cataract formation via oxidative damage ?
oxidaation of sugars to dicarbonyl compounds that may cause oxidation of glutathione, protein SH grps, and inhibition of PPP, oxidation of mem. lipids and may impair membraine transport and permeability
mechanism of cataract formation via ionizing radiation
decreased glutathionine, increased calcium which promotes 43Kd protein binding to PM, and crystallins bind to protein forming light scattering aggregates
senile cataract mechanism
reduced glutathionine levels
modifcation of lens permeability
modification of lens proteins
where are the mitochondria lacking
in the greatest area of visual acuity
the retina has a high requirement for
protein and phosphilipid biosynthesis (retina is constantly renewed)
macular degeneration is associated with what part of the eye
retina
dry AMD
slow progression
cells of macula break down (deposits of drusen)
wet AMD
rapid progression
blood vessels grow beneath macula-fragile and leak
