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Ocular Phys Block 9 > Corneal Metabolism And UV Absoprtion > Flashcards

Corneal Metabolism And UV Absoprtion Flashcards

1
Q

Considerations of glucose metabolism in the cornea

A

Glucose source

O2 availability

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2
Q

Active pathways of glucose metabolism in the cornea

A
  • glycolysis
  • TCA/Krebs cycles
  • HMP shunt
  • ETC
  • glycogen storage
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3
Q

Metabolic distress in corneal metabolism

A

Low O2

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4
Q

Where does most glucose come from

A

Aqueous humor

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5
Q

Where is the glucose from the aqueous humor supplied to

A

Epithelium and endothelium

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6
Q

Where is a minor supply of glucose to the cornea from

A

Tears and limb always capillaries

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7
Q

In what corneal layer can glucose be derived from glycogen

A

Epithelium

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8
Q

During glycolysis, 1 glucose molecule will produce

A
  • a net gain of 2 ATP

- 2 Peruvic acid

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9
Q

During the krebs cycles and ETC complete oxidation _______ ATP are produced

A

36

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10
Q

How many ATP produced from lipids

A

136

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11
Q

Where are all the possible places the cornea can get glucose

A

Aqueous humor
Tears
Glycogen in epithelium

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12
Q

Where does corneal epithelium get O2

A

Mostly from the atmospheric O2 found in the tear film

Some from the limbus

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13
Q

Where does the corneal endothelium obtain O2

A

From the aqueous humor

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14
Q

Aerobic condition

A

ETC

Normal environment with adequate O2

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15
Q

Anaerobic condition

A

Only glycolysis

Reduced O2, requires restricting metabolism

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16
Q

What is needed for corneal regeneration

A

Need DNA, AA, fatty acids. The primary reason of moderate activity in the cornea is because it is constantly regenerating

17
Q

When is lactate produced

A

Anaerobic metabolism

18
Q

Important for the production of a variety of components required for the rapid regeneration of new corneal epithelial cells that are constantly being produced. Acquiring these components from the vasculature is very limited

A

HMP shunt

19
Q

What does the HMP shunt do

A
  • Produce intermediates for nucleotide production, used n DNA replication
  • produce some amino acids
20
Q

HMP shunt and ATP

A

Less ATP produced in contrast to that from the ETC, but important biomolcules are generated

21
Q

Reduced O2 levels int he cornea

A

Can restrict metabolism to anaerobic glycolysis

22
Q

Lactate in the cornea

A
  • diffuses into the stroma
  • causes osmotic stress
  • induces epithelial and stromal edema
23
Q

Clinical complaints of lactate in the cornea (low O2)

A
  • halo and rainbow type visual anomoles
  • increased glare
  • decrease CS
24
Q

Chronic effects of reduced O2 in cornea

A
  • corneal edema
  • Limbal redness
  • vascular response
  • epithelial microcysts
  • endothelial plymegethism
25
Q

What might be some different causes of lack of O2 in the cornea

A

CL wear abuse

Sleep

26
Q

A painful eye condition caused by exposure of insufficiently protected eyes to the UV rays from either natural or artificial sources

A

Photokeratitis or UV keratitis

27
Q

What wavelengths can cause photokeratitis

A

Less than 400nm

28
Q

What wavelengths damage the epithelium

A

Shorter wavelengths

29
Q

What wavelengths damage the endothelium and the more posterior ocular structures

A

Longer wavelengths

30
Q

Low level exposure to UV in the cornea

A

Inhibited cell mitosis

31
Q

Medium to high level exposure of UV to the cornea

A

Swollen nuclei and cell death

32
Q

Extreme level exposure of UV to the core an

A

Complete sloughing of epithelial cells

At higher levels of damage, O2 contributes to the damage

33
Q

UV light damage causes what to DNA

A

Pryrimidine dimers

-usually thymine dimers

34
Q

DNA repair

A
  • UV specific endonuclease (exinuclease)
  • cuts DNA on both sides of damage
  • removes damaged region
  • gap filled in by repair DNA polymerase
  • DNA ligament seals backbone
35
Q

Zero dream pigmentosum

A

Deficiency in the excision endonuclease and a reduced ability to repair damage from UV light and other effectors

36
Q

What is xeroderma pigmentosum a defect in

A

Excision endonuclease

37
Q

Symptoms of xeroderma pigmentosum

A
  • increased risk of cancer
  • eye lid scarring
  • corneal ulceration

Ocular Phys Block 9 (5 decks)

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