Biochemistry - Metabolic Profile of the Eye Flashcards
(38 cards)
Where can there be no oxidative metabolism in the eye?
In the path of light, therefore the lens and fovea are out.
What are 4 functions of the cornea?
1) Structure
2) Ion transport
3) energy production
4) Anti-oxidant system
What lies between collagen fibers keeping them in orderly arrays.
Keratan sulphate I (GAG). Fiber array minimizes light scattering
Glaucoma treatment:
what does prostaglandin analogs do?
Increase outflow (ex. Latanoprost -xalatan)
Glaucoma treatment:
What do B-blockers do?
Reduce secretion ( Timolol - Timoptic)
Glaucoma treatment:
What do cholinergic agonists do?
Restore outflow after an acute attack.
Glaucoma treatment:
What does Carbonic Anhydrase inhibitors do?
Reduce secretion
Systemically via acetazolamide (diamox)
Topical via dorzolamide (trusopt)
**Cosopt is a comb of timolol and dorzolamide
What is posterior Vitreous Detachment?
-Common in elderly it can result in seeing flashing lights and “floaters” due to shrinkage and collapse of vitreous. Normally with age vitreous becomes more liquid and falls aways from the retina.
What are the 2 main ingratiates in the composition of the cornea?
- Water (78%) critical to transparency
- collagen (15%) type I
What transport system in the cornea protects the eye from GAG’s natural tendency to uptake water?
Active transport of bicarbonate out into aqueous humour counteracts this and keeps the aqueous humour hypertonic with respect to teh cornea and maintains corneal transparency
***requires ATP
What is the main metabolic process of glucose in the eye?
- 60% foes to HMP shunt and 35% anaerobic glucolysis, and 5% goes to aerobic glycolysis + TCA cycle
What can occur with prolonged wearing of contact lenses?
- hypoxia:
- -> increased lactate production
- -> decreased corneal pH
- -> Corneal swelling
What are the main functions of the anti-oxidant system in the cornea?
- Removes superoxide
- Removes peroxide
- Reduces disulphide bridges (in proteins)
- Maintains reduced (active form of glutathione.
What is the main energy producing system that supports the anti-oxidant system?
- pentose phosphate pathway
What are the main functions of the Aqueous humor?
- Secreted by the ciliary processes into the posterior chamber
- Drains out through the canal of Schlem
- Brings nutrients to the cornea and lens
- Removes metabolic end products from the cornea and lens.
What is the main composition of Aqueous humor?
- Glucose (80% plasma), lactate (3-4x plasma), Ascorbic acid (10-50x)
- *High glucose and ascorbic acid due to anaerobic activity.
What is the leading cause of preventable blindness?
- What are the two types of the above disease?
- What is the leading cause of non-preventable blindness.
- Glaucoma
- decrease in drainage (most common) or overproduction
- Macula degeneration
What are the 3 types of glaucoma that results in a decrease in drainage?
- Primary open angle glaucoma (blockage in drainage canals)
- narrow angle glaucoma (Angle closure - outer edge of iris blocks entrance to canals, chronic and acute forms)
- Normal tension glaucoma - optic nerve damage despite normal IOP
What are some risk factor for Glaucoma?
- African ancestry
- Family history
- Diabetes
- Severe myopia
- Age > 45 years
- Prolonged use of steroids
- Previous eye injury
Trace the circulation of aqueous humor in the eye?
- Aqueous humor is secreted at the ciliary body circulates through the posterior and anterior chambers before it is reabsorbed through the canal of Achlemm
What are the functions of the vitreous humor in the eye?
- Support function
- metabolic “carrier” for retina
- Gelatinous mass (not fluid)
- Low Concentration of macromolecules
- Fibrillar network - largely proteoglycans, hyaluronic acid, and collagen
What is the composition mainly composed of?
- Water (99%)
- Collagen (mostly type II) - form sparse network
- Proteoglycans (especially chondroitin sulphate)
- Hyaluronic acid
- Ascorbic acid (10 x plasma)
In the vitresous humour structure what holds the collagen fibrils apart?
- What holds these apart?
- proteoglycan bridges
- hyaluronic acid holds bridges apart while maintaining sparse meshwork
What is the makeup of the lens?
Is there blood supply to the lens?
What are some other feature of the lens?
- Mostly water (66%) and proteins (33%)
- No blood supply (low in oxygen)
- High glutathione content, high cholesterol content, grows throughout life and cells don’t turn over, receives nutrients and voids wastes via aqueous humor.
