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CLO > Cornea > Flashcards

Cornea Flashcards

(40 cards)

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1
Q

6 Layers of the cornea

A

Epithelium

Anterior limiting lamina

Stroma

Dua’s layer

Posterior limiting lamina

Endothelium

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2
Q

Thickness: Epithelium

A

55um

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3
Q

Thickness: Anterior limiting lamina

A

8-10um

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4
Q

Thickness: Stroma

A

500um

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5
Q

Thickness: Dua’s layer

A

15um

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6
Q

Thickness: Posterior limiting lamina

A

8-10um

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7
Q

Thickness: Endothelium

A

5um

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8
Q

Corneal: Width

A

11.6mm

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9
Q

Corneal: Anterior height

A

10.6mm

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10
Q

Corneal: Centre thickness

A

540um

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11
Q

Corneal: Edge thickness

A

0.7mm

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12
Q

Corneal: Anterior radius

A

7.8mm

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13
Q

Corneal: Posterior radius

A

6.7mm

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14
Q

Corneal: Refractive index

A

1.376

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15
Q

Corneal: Refractive power

A

~42D

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16
Q

Corneal Overview

A

Transparent outer coat

Several layers of connective tissue

Avascular and specialised structure = transparency

Mechanical protection and sensory innervation = blink reflex

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17
Q

What can reduce corneal sensitivity

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A

Systemic diseases like diabetes

18
Q

What can innervation damage cause

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A

Anaesthesia - loss of reflex lacrimation and lid closure

19
Q

Corneal innervation

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A

Nerve fibres on cornea unmyelinated for transparency

Schwann cells myelinate nerves towards peripheral cornea

Leaves as bundles to join ciliary nerve from ophthalmic branch of trigeminal nerve

20
Q

Cell types making up epithelium

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A

Squamous cell - 2 layers

Wing cell - 2 to 3 layers

Columnar cell - 1 layer

21
Q

Features: Epithelium

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A

Stratified

Non keratinised

5-6 layers

Made up of 3 different cells

22
Q

What structures are involved in corneal healing

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A

Epithelium

Stroma

Nerves

Lacrimal glands

Tear film

23
Q

Name the 4 phases of corneal healing

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A

Latent phase

Migration

Proliferation

Attachment

24
Q

Healing times for superficial damage and full thickness defect

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A

24hrs for superficial

7 days for full defect

25
At what point does scarring occur
Damage deeper than anterior limiting lamina will heal but scar
26
Latent phase (5)
Lacrimal glands change tear makeup/quantity Growth factors released from tears Damaged cells go through cell death process Fibres aid adhesion or migrating cells Desmosome attachments weaken
27
Migration
Surrounding cells flatten and slide together along wound bed Miosis does not occur yet
28
Proliferation
Cells proliferate upwards Cell division accelerated - new cells move upward Zonular occlusions form 1st, epithelial 2nd and then glycolax
29
Attachment
Restoration and attachment of desmosomes and heridesmosomes Wound closure 2-4 days - full attachment full week
30
Function: Epithelium
Smooth hydrophilic refracting surface Metabolic exchange and pathogen/bacteria protection Rapid regeneration/mechanical protection - blink reflex
31
Function: Anterior limiting lamina
Anchor site for epithelium Tough layer for mechanical support
32
Features: Anterior Limiting Lamina
8-10um thick Acellular zone with collagen fibres Posteriorly woven with anterior stroma Sensoru nerve fibres to innervate epithelium Layer separates epithelial growth factors to avoid scarring
33
Function: Stroma
Mechanical strength and stability Maintains homogeneity for transparency Regularity of fibre arrangements produce diffraction grating
34
Features: Stroma
Formed with layers of collagen and fibroblasts between Collagen fibrils evenly spaced in parallel bands Layers include keratin sulphates to aid corneal hydration
35
Location of Dua's Layers
Between stroma and posterior limiting lamina
36
Features: Dua’s Layer
Layers of collagen laying in longitudinal, transverse and oblique direction Made up of 5-8 layers Very strong ~700mmHg before rupture Important for glaucoma treatment response and keratoplasty surgery techniques
37
Function: Posterior limiting lamina
Structural base for endothelium
38
Features: Endothelium
Single layer Metabolically active = many mitochondrias Cannot regenerate Cell membrane creates barrier to prevent free flow Vesicles within regulate corneal hydration and aid transport of metabolites from aqueous
39
Corneal Transparency: Nerves and vessels
Avascular - episcleral loops enter the cornea up to 1mm at limbus Unmyelinated nerves until 0.5mm from the limbus Homogenous refractive index - maintained by consistent water content
40
Corneal Transparency: Features
Regularity of fibrils Parallel spacing = diffraction grating Spaced less than then wavelength of light Light incident normally travels undeviated Light incident at an angle away from the 4mm centre will have reduced transmission UVB/UVC mostly absorbed as their wavelength less than fibril spacing

CLO (13 decks)

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