OcPhysioT2_MS Flashcards
What is the range of IOP?
Average?
Range: 10-22mmHg
Avg: 15.5mmHg
Does the frequency distribution for IOP follow a normal Gausserian curve?
Nope.
It is skewed to the right.
What is the percentage of people who have pressures over 21mmHg?
2.5%
Is central corneal thickness effects more pronounced in stiffer cornea or softer corneas?
Stiffer corneas
THere is a linear relationship.
What does a higher Young’s Modulus correlate to?
It corresponds to a steeper slope.
What is the influence of CCT on IOP measurement dependent on?
cornea biomechanical properties.
What are the long term factors affecting IOP?
Genetics Age Sex Refractive error Race
How is blood able to flow through structures in the eye relating to IOP?
The perfusion pressure of the retina, choroid, and ciliary body must be greater than IOP.
What structure absorbs some amount of IOP?
The uveal tissue. absorbs 2mmHg
What is the total percentage of water in the lens?
66%
This amt is lower compared to other tissues
What percentage of water is contained in the capsule?
Dense nuclear region?
Cortex?
80%
63%
68%
Does the water content change as you age?
Nope
When you have a cataract, does hydration increase or decrease?
Increases
What percentage of the lens is proteins?
33%
Crystallins makes up 90% of that 33%
What is the significance of proteins in lens?
Refractive properties
What are the three types of crystallin proteins?
alpha-crystallin
Beta-crystallin
gamma-crystallin
Is the nucleus or cortical region of the lens richer in alpha crystallins?
Cortical region
Describe the concentration of AA in the lens?
It is much higher in the lens compared to vitreous, aqueous, plasma.
What properties allows AA concentration to decrease in the lens?
Aging
Cataract formation
Reduction in Na+/K pump
What happens to AA with aging?
Racemization
The transformation of the L-isomer form to the D-isomer
What is the most abundant free AA in the lens?
Taurine
What happens when one encounters osmotic stress like Diabetes to taurine?
Down regulation of Na+/taurine cotransport and of AA for GSH biosynthesis.
Is the nucleus or cortical region of the lens richer in gamma crystallins?
The nuclear region
Name some inorganic ions that are more concentrated in the lens compared to the aqueous?
Potassium
Name some inorganic ions that are less concentrated in the lens compared to the aqueous?
Sodium
Chloride
Calcium (50X less)
Which inorganic ions increase in cataract formation?
Sodium
Calcium
Which inorganic ion decrease in cataract formation?
Potassium
Does the level of magnesium change in cataract formation?
Nope, it does not change.
Does the lens have a blood supply?
No
Where does the lens acquire its nutrients?
Aqueous humor.
What is the oxygen consumption of the lens?
Low
Who uses the most oxygen in the lens?
Epithelium
Then cortex
then the nucleus
Which process derives the most energy in the lens?
Glycolysis
Oxygen tension around the lens is low.
Which energy process generate free radicals?
Oxidative phosphorylation
What percentage of ATP generated is used for protein synthesis?
10%
Also used in synthesis of glutathione
Where does 90% of proteins energy go to?
Active transport
Cell division
Biochem pathways to protect the lens from oxidative damage
What is the percentage of glycolysis that takes place in the lens?
80%
Yields 2 molecules of ATP
What is the rate limiting factor in glucose metabolism?
Levels of hexokinase.
Does the levels of hexokinase decrease or increase with age?
It decreases with age.
What does the anaerobic pathway allow the lens to do?
REmain transparent in the absence of oxygen.
Does the Kreb cycle take place in the epithelium or endothelium?
Epithelium.
Has the enzymes and oxygen content.
What percentage of glucose is made from Kreb’s?
20%
What percentage of glucose is derived from Hexose MOnophosphate shunt?
14%
What are pentoses used in?
Nucleic acid synthesis
What is NADPH needed for?
Maintenance of GSH
Cofactor in Sorbitol pathway
WHat does the sorbitol pathway utilize?
NADPH
Aldose reductase
How can sorbitol be detrimental to lens?
Predisposition to cataracts Does not diffuse out of lens fast. Water flows in Swelling Reduction in transparency.
Where is sodium most concentrated in the lens?
In the posterior cortex
Where is potassium most concentrated in the lens?
IN the anterior cortex.
Where is the major site of cation transport in the lens?
In the epithelium, beneath the anterior capsule.
Where does the production of aqueous humor come from?
Ciliary body of nonpigmented epithelium cells. .
What is diffusion?
When a substance is concentrated in one part of the system, the random motions will tend to cause the substance to redistribute itself in time.
Does not require energy.
What does FIck’s law describe?
The net movement of a substance across a semipermeable membrane.
