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Basic Science Block > Fundamental of Cornea > Flashcards

Fundamental of Cornea Flashcards

(55 cards)

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1
Q

List a function of Cornea ?

A

1.Transparent.
2.Refeact light.
3.Contain IOP.
4.Provide a protective.
5.Reparative.

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2
Q

Properties of cornea : Refeactive index ?

A

1.376

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3
Q

Cornea Biology

Spehric
Curvature
Refractive power
Nutrients

A

Aspheric
- Curve
7.8 mm anterior
6.5 mm posterior

  • Refract 43.25 ( 74% )
    Air - Tear 43.6
    Tear Cornea 5.3
    Cornea Aqueous -5.8
  • Nutrients
    Glucose from Aqueous Humor
    Oxygen from tear film and peripheral from limbal
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4
Q

Corneal thickness ?

A

520 - 540 mm
peripheral 670 mm

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5
Q

Surface area of cornea ?
and size

A

1.3 cm2

vertical = 10-11
Horizontal = 11-12

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6
Q

Descripe Optical Zone?

A

Central 1/3 is Optical zone
approx 5.4 mm
in lasik 6.5 mm

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7
Q

Explain Zone of Cornea ?

A

Apical zone
- Central + Paracentral

Transitional zone
- Peripheral zone
- Greates flattening and asphericity

Optical zone
- 5.4 mm and for Lasik 6.5 mm

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8
Q

Component of Cornea ?

A
  • Water
  • Collagen
  • Protein
  • Keratan
  • Chondroitin / dermatan sulphate
  • HA
  • Salts
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9
Q

Which component is abundant in cornea ?

A

Water : 78 %

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10
Q

Describe collagen in cornea ?

A

Type 1 : 50-55 %
Type 3 : 1 %
Type 4 : 8-10 %
Type VI - 25-30 %

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11
Q

Describe Corneal sensation ?

A
  • High density nerve ending
  • > 100 times at conjunctival
    Nerve - Posterior long ciliary nerve
  • Stromal Plexus
  • Subepithelial plexus
  • Intra epithelial plexus
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12
Q

Corneal Blood supply ?

A

Corneal is avascular tissue .

at peripheral 1 mm
- anterior ciliary vessels
so vascular is not in cornea but subconjunctiva surround cornea.

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13
Q

describe Corneal Embryology

A

Wks 4 - Neuroectoderm - Optic Vesicle
Wks 5 - Surface ectoderm > Lens Placode
> Cornea and conjunctiva epithelium
Wks 6 : 1st wave > Corneal endothelium
Wks 7 : Corneal stroma and sclera

Month 2 : Eyelid fuse develop conjunctiva .
Month 3 : All corneal component present except bowmans layer.

Month 6 : Eyelid Open

At birth : Infant globe is 80 % of adult size .

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14
Q

Embryonic origin of cornea ?

A

Corneal epithelium : Surface ectoderm
Bowman Layer : Mesenchyme
Stroma : Mesenchyme and neural crest
Descemet : Synthezide by Endothelium
Endothelium : Neural crest

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15
Q

Fx of corneal epithelium

A

Barrier

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16
Q

Fx of corneal stroma

A

Transparency

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17
Q

fx of corneal endothelium

A

Barrier and metabolic pump

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18
Q

Describe Limbal Stem cell concept ?

A

Migrate from basal of epithelium from peripheral to center.

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19
Q

what type of Epithelium ?

A

Stratified squamous non keratinized
continuos with conjunctiva but no goblet cell .

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20
Q

What is 3 subtype layer of epithelium ?

A

Surface cell
Wing cell
Basal Cel

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21
Q

Proliferation turnover of corneal epithelium ? + Corneal thickness in percent

A

7-14 days , consist of 5 % of corneal thickness

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22
Q

What type of junction between superficial epithelia cell ?

A

Tight Junction which protect penetration injury

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24
Q

What is Deepest cell layer of epithelium

Study These Flashcards
A

Basal cells , Columbar eith rounded heads and flat bases

25
What is the second layer of epithelium
Wing cell , polyhedral shape
26
What is the outermost of corneal epithelium cell ?
Surface cells also polyhedral and hexagonal .
27
Describe the adhesion between each cell of epithelium ?
Surface cells - Tight Jx with desmosome Winger and Superficials - Desmosomes Basal Cells - Desmosome and hemidesmosome
28
What is Basal Lamina ?
Create by basal cell of epithelium , structure to 2 part Lamina lucida + Lamina Densa Consist of type IV collagen and laminin Stromal edema or inflammation mayloosed the cohesion between Bowman and Basal lamina
29
Explain Epithelial Repair ?
30
Describe Bowman Layer ?
Acellular , modified anterior stroma - Compact of collagen > strength - No regeneration > Scar tissue
31
Describe Stroma
90 % Corneal thick ( 500 mm ) Collagen + Proteoglycan Lamellae are arranged in layers Less cell - Keratocyre is present
32
What stroma composed of ?
Collagen Type I , V , VI Proteoglycan - Decorin ( Dermatan sulfate ) - Lumican ( Keratin sulfate )
33
Clarity of cornea depend on what ?
1. Tigh pack of epithelium > Produce a layer of uniform refrative + minimal light scattering 2. Regular arrangement of stroma cells 3. Lattice arrangement of collagen fibrils > Minimal light scattering 4.Keep water content in corneal stroma
34
Describe Stromal repair ?
Keratocytes activation > Migration and tranform in to fibroblast > Production of scar > Remodelling of scar > Thinning of fibrils + Reformation of lamellae > Increase in transparency
35
Describe Descemdt membrane ?
Strong resistant sheet composed of Type IV collagen thicken with age and in some corneal degeneration Termination of DM : Scwalbe lines > Hypertrophied in congenital anomalies - posterior embryotoxon
36
When Descemet membrane is create ?
anterior 1/3 : as fetal Posterior 2:3 : after birth
37
Describe Repair of descemet ?
Trauma of DM Endothelium spread cell to resurface > synthesis of basal lamina > identical to bormal descemet
38
Describe Cell in Endothelium ?
Mosaic pattern as Hexagonal . - Cell density is highest in periphery . at youth is hexagonal at age is polymorphic
39
What is Desmatocele ?
40
Endothelium energy and nutrients ?
Large number of mitochondria + nutrition and o2 from aqueous
41
Describe fluid regulation of stroma by endothelium ?
Barrie function of salt to stroma Pumping Bicarbonate io s out of stroma to aqueous - NaK - NaH
42
Endothelial repair ?
Injury > loss of cells Neighbour cell > Migrate and enlargement > after injury number of cell decreas , Cell area increase , cell height decrease
43
Describe Cornea nutrition ?
Oxygen from tear film Glucose amino avode vitamins from aqueous
44
3 metabolic pathways
1.Penntose Shunt 2.Glycolysis 3.TCA or Krebs or citric acide
45
Corneal Transparency achieved by ?
1.Regular arrangement of stromal lamella 2.Cornea Epi and tear film Epi - non keratinize + Regular and uniform arrangement 3.Corneal avascularity 4. Non myelated nerve fibers 5. Proper corneal hydration
46
Corneal hydration mechanism ?
- Stromal Swelling pressure by GAG - Endo and epi is protection - Endothelium active pump - Evaporate from corneal surface - IOP if IOP > SP = Corneal edema IOP > 55 = epithelial edema IOP > 30 ( cct > 0.6 ) = Epithelial edema
47
Factors Affecting drugs to cornea
1.Lipid and water aolubility 2. Molecular size wt and conc 3.Ionic form of drug 4.pH of the solution 5.Tonicicty of solution 6.Surface active agents 7.Pro - drug form
48
Describe Corneal dye
Fluorescine and lissamine green
49
what is the different of papillae and Follicles ?
Papillae have mid vessels Follicles have none
50
When will you see DCM ?
if corneal thickness increase 10 %
51
When will Epithelial edema ?
If thickness exceed 700 microns
52
What is the number of good cornea ?
not exceed 650 if > 650 will leas to post op complication.
53
What is Estheiometty ?
To toch corneal senaation . ( Cranial Nerve V
54
Tell the number of endothelial cell count in normal .
Cell density At birth 3000-4000 Middle age 2400-2500 Old 2000 Mean cell size : 150-350 CV < 0.3 % of hexagonal = 100 %
55
Preop corneal should have
ECc > 1000-1200 CV : < 0.4 Hexagonality : > 0.5 Good donor cornea should endothelial > 2000

Basic Science Block (3 decks)

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