MT2 Info Flashcards
the major nutrients glucose and oxygen are in:
tears, gimbal blood vessels, aqueous humor
glucose is not permeable to:
superficial epithelium
glucose must get to the cornea via:
aqueous humor
glucose uptake across the endothelium must be
facilitated diffusion
about how much of the glucose used by the corneal epithelium is metabolized to lactate under normal conditions
65-85%
about how much of the corneal glucose is used for aerobic (Kreb’s cycle) and what percent of ATP is produced with this method?
15-35% of the glucose is used to make abut 60-70% of ATP
when is more lactate produced?
when the epithelium is made hypoxic (ex: during contact lens wear)
when the eye is closed, how does the oxygen flow out?
diffuse out of the palpebral capillaries to the tears
oxygen flux from the aqueous to the cornea is especially important when:
the eye is closed
oxygen consumption rate is highest in the
endothelium
oxygen consumption rate is lowest in the
stroma
what % of oxygen is used in the corneal endothelium?
21%
what % of oxygen is used in the corneal epithelium?
40%
what % of oxygen is used int he corneal stroma?
39%
in the open eye, the pO2 is what for tears and aqueous humor?
pO2= 155 mmHg for tears pO2= 55 mHg for aqueous humor
oxygen tension (P) =
(QX^2 / 2Dk) + BX + C
the mathematical determination of diffusion through the lens is called:
Fick’s Law
Dk/L represents the:
oxygen transmissibility of the lens
how does a lower Dk value of a cL affect oxygen getting to the eye?
decreases oxygen supplied to front of eye
how does increased CL lens thickness affect oxygen getting to the eye?
decreases oxygen supplied to front of eye
higher Dk/L value= ___oxygen getting through CL
more oxygen
what else has an affect on determining oxygen under a CL other than Dk/L?
blinking
some studies suggest a minimum Dk/L value for daily wear as:
25
some studies suggest a minimum Dk/L value for extended wear as:
85, maybe even 125
how many of the tears are refreshed with each blink?
20% of tears
what are some affects on cells when they are made hypoxic?
ATP production from mitochondria slows and glycolysis speeds up to try to maintain the ATP supply
when the cells become hypoxic and ATP production from mitochondria slows and glycolysis speeds up, what is it called?
Pasteur effect
what is the result of the Pasteur effect?
lactate and proton production will increase and glucose consumption will increase
what are the factors limiting the rate of glycolysis under hypoxic conditions?
glucose supply, diffusion, glycogen stores
in severe hypoxia, what can epithelial cells store and for how long?
they can store glycogen which will last about 2 hours in severe hypoxia
corneal epithelial “haze” in hypoxic CL conditions is subjectively described as:
color fringes around bright lights
Sattler’s Veil
