Term
| What is the major fuel of the eye? |
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Definition
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Term
| Why is ATP produced in the eye? |
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Definition
| Tissue growth and maintenance, ion transport, GTP for its role in the visual cycle |
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Term
| How is most ATP in the lens produced? |
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Definition
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Term
| What composes the stroma of the cornea? |
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Definition
| Hydrated matrix of collagen (Type I) and proteoglycans (GAGs- Keratan Sulphate I, Chondroitin Sulphate) |
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Term
| The accumulation of what causes corneal clouding? In what syndromes? |
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Definition
GAGs-
mucopolysaccharidoses, like HURLER and SLY SYNDROME |
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Term
| How is the tendency of GAGs to promote water uptake and disrupt the arrangement of corneal fibers counteracted? |
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Definition
| Aqueous humor is hypertonic, aided by the pumping of HCO3- out of the cornea |
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Term
| What happens if water content in the cornea is increased beyond the normal 78%? |
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Definition
| it gets thicker and CLOUDY |
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Term
| Besides maintaining appropriate water levels, how else is clarity of the cornea maintained? |
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Definition
| Large amounts of VEGFR-3 to prevent growth of blood vessels |
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Term
| What are the main requirements for ATP in the cornea? |
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Definition
| Ion transport and synthesis of matrix components |
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Term
| In the cornea, how is glucose metabolized? |
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Definition
40% glycolysis
35% anaerobic and 5% oxidatively
60% Pentose Phosphate pathway, making NADPH |
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Term
| Why is NADPH production important in the cornea? |
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Definition
To prevent or reverse photooxidation
Glutathione reductase requires NADPH as a coenzyme |
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Term
| What are the functions of the antioxidant system in the cornea? |
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Definition
Remove superoxide (free radicals)
Remove hydrogen peroxide
Reduce disulfide bridges |
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Term
| How are metabolites supplied to the cornea? |
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Definition
Aqueous humor
oxygen diffuses through the anterior surface from tears |
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Term
| What are the consequences of prolonged wearing of contact lenses? |
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Definition
Hypoxia under the lens- increased lactate production and decreased corneal pH
Corneal Swelling |
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Term
| What is the function of the aqueous humor? |
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Definition
| To bring nutrients to the cornea and lens and remove end products to the blood stream |
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Term
| What secretes aqueous humor, and how? |
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Definition
Ciliar processes- active transport of sodium ions with bicarbonate and Cl- to maintain electrical neutrality
This brings osmosis of water |
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Term
| How does aqueous humor drain into the bloodstream? |
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Definition
| Trabecular meshwork into the canal of Schlemm- constantly flowing |
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Term
| What composes the vitreous humor? |
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Definition
| Gelatinous mass held together by a fine fibrillar network of Collagen Type II, Proteoglycans (Chondroitin Sulfate) and Hyaluronic Acid |
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Term
| What holds the proteoglycan bridges apart in the vitreous humor? |
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Definition
| Hyaluronic Acid- maintains the structure |
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Term
| What is Posterior Vitreous Detachment? |
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Definition
A cause of flashing and floaters- ELDERLY
-with age, vitreous humor loses its gel-like consistency, shrinks, collapses, and separates from teh retina |
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Term
| What is damaged in glaucoma, and what is the general cause of the damage? |
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Definition
| Optic Nerve- Increased intraocular pressure due to decreased drainage |
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Term
| What is Normal Tension Glaucoma? |
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Definition
Occurs with normal intraocular pressure
Etiology Unclear |
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Term
| What is the most common form of glaucoma? |
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Definition
| Primary Open-Angle Glaucoma- decreased drainage of aqueous humor caused by clogging of the canal of Schlemm |
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Term
| What are the types of drugs given for glaucoma? |
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Definition
Prostaglandin analogs (latanoprost)
Beta Blockers (Timolol, Betaxolol)
Cholinergic Agonists(Pilocarpine)
Carbonic anhydrase inhibitors (acetazolamide or methazolamide) |
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Term
| What is the mechanism of prostaglandin analogs in treating glaucoma? |
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Definition
| Latanoprost- increase outflow/drainage of aqueous humor |
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Term
| What is the mechanism of Beta blockers in treating glaucoma? |
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Definition
| Timolol, betaxolol- reduce secretion of aqueous humor |
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Term
| What is the mechanism of cholinergic agonists in treating glaucoma and when do we use them? |
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Definition
| Pilocarpine- restore resorption of outflow- used in ACUTE attacks |
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Term
What is the mechanism of carbonic anhydrase inhibitors in treating glaucoma?
PAY ATTENTION- CHEWY LOVES THIS ENZYME |
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Definition
| Acetazolamide or methazolamide- decrease the rate of bicarbonate production and, as a result, aqueous humor secretion |
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Term
| What is angle closure (narrow angle) glaucoma? |
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Definition
Outer edge of iris protrudes over the drainage canals for the aqueous humor- treated surgically-
Less common in A.A. patients |
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Term
| What is the relationship between lens crystallins and hydration? |
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Definition
| More hydrated= less transparent |
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Term
| How is MOST of the glucose in the lens used to make ATP? |
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Definition
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Term
| What antioxidant is present in high levels in the lens, in addition to the normal NADPH mediated pathway? |
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Definition
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Term
| What are cataracts, and what are some risk factors? |
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Definition
Opacity of the lens caused by protein aggregation
Diabetes, galcatosemia, radiation, smoking, high fat diet, certain drugs, genetics |
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Term
| What pathway reduces alcohols in the lens and can lead to the accumulation of sorbitol causing cataracts? |
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Definition
| Polyol Pathway- Aldose Reductase |
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Term
| How does excess sorbitol cause cataracts? |
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Definition
| Accumulation of sorbitol causes osmotic uptake of water, crystallins become more hydrated, aggregation and light scattering results |
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Term
| What is the proposed mechanism for radiation (X-ray) induced cataracts? |
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Definition
| Decreased reduced glutathione, increase in cellular Ca, promoting binding of a protein (MW43kDa) to the membrane that forms a focus for the aggregation of crystallins |
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Term
| What causes senile cataracts? |
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Definition
| Age-related modification and breakdown of lens proteins- reduced glutathione levels and changes in membrane permeability |
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Term
| How does oxidative damage cause cataracts? |
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Definition
| Glutathione gets oxidized, PPP gets inhibited |
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Term
| How does the retina produce ATP? |
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Definition
Anaerobic glycolysis
ALSO, oxidative metabolism
It is vascularized, but not near the fovea |
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Term
| What other biomolecules are present in the retina, and why are they important? |
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Definition
| Vitamins A and C- roles in the visual cycle, as well as prevention or reversal of photooxidation |
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Term
| What is the leading cause of blindness in the elderly? |
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Definition
| Age-related macular degeneration |
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Term
| What are the two forms of macular degeneration? |
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Definition
Dry AMD- cells of macula slowly break down- most common- yellow deposits of "drusen"
Wet AMD- blood vessels grow beneath the macula that are fragile and leak blood |
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Term
| What are some methods of treating macular degeneration? |
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Definition
Anti-oxidant vitamins to inhibit progression
Laser treatment for wet AMD
Injection of VEGF inhibitiors |
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