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Ophthalmology > The Cornea > Flashcards

The Cornea Flashcards

1
Q

Layers of the cornea

A
  1. Praecorneal tear film
  2. Epithelium
  3. Stroma
  4. Descemet’s membrane
  5. Endothelium

Completely transparent & avascular

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2
Q

Cornea: Oedema

A
  • Accumulation of fluid in the stroma
  • Impaired function of the epi- and/or endothelium
  • Water molecules enforce fibres and cells
  • Grey-blue opacity; Focal or diffuse
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3
Q

Cornea: Vascularisation

A
  • During both pathologic & healing processes
  • Superficial/deep/mixed
  • Type of vascularisation depends on the depth of the corneal process
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4
Q

Cornea: Pigmentation

A
  • Pigment deposition in the epithelium & stroma
  • Migration of melanocytes & pigment-filled macrophages from the limbus
  • Causes: Chronic corneal irritation; Desscication; Exposition
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5
Q

Cornea: Ulceration

A
  • Superficial or deep excavation in the corneal tissue
  • At the site of the ulcer, corneal tissue is lost
  • Deep ulcers may lead to corneal perforation
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6
Q

Cornea: Infiltration

A

Features of infiltration are dependent on the cause:

  • Leukocytes & granulocytes → Infection
  • Eosinophils → Allergy; Antigen-caused
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7
Q

Cornea: Scar formation

A
  • Reparation of gaps in the stroma
  • After scarring, irregular arrangement of collagen fibres → Opacity
  • Kerectasia
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8
Q

Cornea: Types of scars by size

A
  1. Nebula
  2. Macula
  3. Leucoma
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9
Q

Cornea: Kerectasia

A

Severe granulation due to chronic irritation

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10
Q

Corneal congenital opacity: Aetiology

A

Inherited; Intrauterine infection

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11
Q

Corneal congenital opacity: CSx

A
  • Grayish opacities
  • Shape, size and placement varies
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12
Q

Corneal congenital opacity: Treatment

A
  • Limited
  • Vision is not severely impaired
  • No progression of the disease
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13
Q

Keratitis

A

Inflammation of the cornea

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14
Q

Keratitis can be classified by…

A
  • Aetiology
  • Depth
  • Appearance
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15
Q

Keratitis: Classifications by aetiology (10)

A
  1. Infectious
  2. Traumatic
  3. Allergic
  4. Associated with systemic disease
  5. Mechanical
  6. Chemical
  7. Irritation
  8. Desscication
  9. Innervation abnormalities
  10. Chronic corneal oedema
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16
Q

Keratitis: Classification by Depth

A
  • Superficial
  • Interstitial
  • Deep
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17
Q

Keratitis: Classification by appearance

A
  • Ulcerative
  • Non-ulcerative
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18
Q

Ulcerative keratitis

A

Ulcer formation in the cornea

  • Superficial/deep excavation
  • Gap in the corneal epithelium & stroma
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19
Q

Superficial corneal ulcers can be sub-divided into…

A
  • Uncomplicated & simple
  • Indolent (causing little pain)
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20
Q

Deep corneal ulcers can be subdivided into…

A
  • Uncomplicated; Non-melting
  • Melting
  • Desmetocele
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21
Q

Uncomplicated, superficial corneal ulcer: CSx

A
  • Mild lacrimation
  • Blepharospasm
  • Perifocal oedema
  • If the upper stroma is exposed: Fluorescein positive
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22
Q

Uncomplicated, superficial corneal ulcer: Treatment

A
  • Eliminate the cause
  • Antibiotic eyedrops
  • Topical vitamins

Heals withing 10-14 days

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23
Q

Indolent, superficial corneal ulcer: Synonyms

A
  • Superficial corneal erosion syndrome
  • Indolent corneal ulcer
  • Refractory corneal erosion
  • Boxer ulcer
24
Q

Indolent, superficial ulcer: Healing time

A
  • Heals slowly/poorly/not at all
  • Tend to recur
25
Q

Indolent, superficial ulcer: Aetiology

A

Hereiditary

  • Separation of the stroma & epithelium
  • Due to inadequate development of hemidesmosomes
26
Q

Indolent, superficial ulcer: CSx

A
  • Lacrimation
  • Blepharospasm
  • Undermined lip / “rolled-up” appearance of the epithelium
  • Exposed stroma
  • Fluorescein positive
  • Vascularisation is rarely stimulated
27
Q

Indolent, superficial ulcer: Treatment

A

Surgery:

  • Grid keratotomy
  • Superficial keratectomy + third eyelid flap
  • Post operative management

Medical therapy is contraindicated

28
Q

Non-melting, deep corneal ulcer: CSx

A
  • Pain
  • Mucupurulent/purulent discharge
  • Deep excavation in the corneal (well-defined edge)
  • Fluorescein positive
  • Perifocal/diffuse corneal oedema
  • Circumcorneal vascularisation
  • Secondary uveitis
29
Q

Non-melting, deep corneal ulcer: Treatment

A
  • Eliminate the cause
  • Medical therapy: Atropine; Abx; Vitamins
  • Surgery
30
Q

Melting, deep corneal ulcer: Pathogenesis

A

Formation of proteases & collagenases from:

  • PTF leucocytes - Abnormal secretion
  • Destroyed corneal epithelium & fibroblasts
  • Bacteria (Pseudomonas spp.)

Stroma becomes solved → Melting → Ulcer → Corneal perforation

31
Q

Melting, deep corneal ulcer: CSx

A
  • Severe pain (blepharospasm & photophobia)
  • Purulent discharge
  • Diffuse corneal oedema
  • Grey-white, gelatin-like material at the base of the ulcer
  • Hypopyon
  • Secondary uveitis
32
Q

Melting, deep corneal ulcer: Treatment

A
  • Emergency intervention
  • Elimination of the cause
  • Surgery:
    • Microsurgery + Enzyme elimination
    • Chemical coagulation - Jodine; Phenol

Medical therapy is contraindicated!

33
Q

Descmetocele: Define

A

Form of ulcer where the stroma has thinned so much, that the integrity of the eyeball is maintained only by the Descemet membrane

34
Q

Descemetocele: CSx

A
  • Black & shining
  • Mucopurulent discharge
  • Pain
  • Staining by fluorescein
35
Q

Descemetocele: Treatment

A
  • Emergency intervention
  • Eliminate the cause
  • Medical therapy is contraindicated
  • Surgery: Direct suturing of cornea
36
Q

List the operative treatment techniques of deep corneal ulcers

A
  1. Grid keratotomy
  2. Pedicle conjunctival graft transposition
  3. Free island conjunctival graft transplantation
  4. Direct suturing of the cornea
37
Q

Supportive techniques in the therapy of deep corneal ulcers

A
  • Third eyelid flap
  • Tarsoraffy (subpalpebral drainage)
  • Post-operative mediation: Atropine; Abx; NSAID
  • Physical protection of the eye
38
Q

Special forms of ulcerative keratitis

A
  • Multipunctional keratitis
  • Herpetic keratitis
  • Corneal sequestrum
39
Q

Infectious bovine keratoconjunctivitis: Aetiology

“Pink eye”

A
  • Moraxella bovis (via flies)
  1. Adheres to the cornea
  2. Haemolysin, dermo-necrolysin & collagenase
  3. Ulceration & necrosis of the cornea
40
Q

Infectious bovine keratoconjunctivitis: Summary

“Pink eye”

A
  • Frequent disease
  • Deep, melting & necrotic ulcer
41
Q

Infectious bovine keratoconjunctivitis: CSx

A
  • Uni-/bilateral
  • More severe in summer & young animals
  • Pain & lacrimation
  • Central corneal ulcer
  • Diffuse, pinkish corneal opacity
  • Corneal vascularisaiton
  • Descemetocele, corneal perforation, phthitis
42
Q

Infectious bovine keratoconjunctivitis: Treatment

A
  • Separation of diseased animals using fly repellants
  • Sub conjunctival depocillin/tetracycline
  • IV sulphonamides
  • Tarsorraphy/third eyelid flap (if severe)
  • Subconjunctival steroids
43
Q

Non-ulcerative keratitis: Definition

A

Inflammation of the superficial/ deeper layers of the cornea without ulcer formation

  • Uberreiter’s syndrome
  • Pigmentary kereatitis
  • Endothelial syndrome
44
Q

Überreiter’s syndrome: Synonyms

A
  • Chronic immune-mediated KCS
  • Chronic superficial keratitis
  • Pannus

Usually seen in German Shepherds

45
Q

Überreiter’s syndrome: Aetiology

A

Unknown; Autoimmune; Role of UV radiation & viruses

  • Proliferation of epithelial cells
  • Infiltration of the superficial stroma by plasma cells & lymphocytes
  • Vascularisation & lipid deposition; Pigmentation, oedema; Scar tissue formation
46
Q

Überreiter’s syndrome: CSx

A
  • Bilateral
  • Temporal inferior corneal quadrant will be opaque
  • Opacity will gradually move centrally → Whole cornea
  • Opacity appears red-grey/black
  • Fluorescein negative
  • May have a “third eyelid form”
47
Q

What is shown?

A

Überreiter’s syndrome: Third eyelid form

48
Q

Überreiter’s syndrome: Treatment

A

Cannot be cured

  • Medical management:
    • Subconjunctival & topical steroids
    • Topical cyclosporin
  • Surgical management:
    • Superficial keratectomy
    • Post-operative therapy
49
Q

Trauma to the cornea: Aetiology

A
  • Biting
  • Scratching
  • Kicking
  • Accident
  • Foreign body
  • Surgery
50
Q

Trauma to the cornea: CSx (superficial)

A
  • Loss of epithelium
  • Oedema
  • Pain
51
Q

Trauma to the cornea: CSx (Deep)

A
  • Deep gap in the stroma
  • Diffuse oedema
  • Opacity
  • Severe pain
  • Discharge

Perforation/laceration?

52
Q

Trauma to the cornea: Perforation

A
  • Full thickness injury of the cornea with outflow of aqueous humor
  • Severe pain
53
Q

Trauma to the cornea: Perforation-laceration

A
  • Perforation together with widespread rupture
  • Prolapse of the iris-lens vitreous
  • Severe pain
54
Q

Trauma to the cornea: Treatment (Superficial & deep)

A

Similar to ulcer therapy

55
Q

Trauma to the cornea: Treatment (perforation)

A
  • Surgical therapy
  • Conjunctival graft; Direct suturing

Ophthalmology (9 decks)

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