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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
Indolent, superficial ulcer: **Aetiology**
Hereiditary * Separation of the stroma & epithelium * Due to inadequate development of hemidesmosomes
26
Indolent, superficial ulcer: **CSx**
* Lacrimation * Blepharospasm * Undermined lip / "rolled-up" appearance of the epithelium * Exposed stroma * Fluorescein positive * Vascularisation is rarely stimulated
27
Indolent, superficial ulcer: **Treatment**
**Surgery:** * Grid keratotomy * Superficial keratectomy + third eyelid flap * Post operative management *Medical therapy is contraindicated*
28
Non-melting, deep corneal ulcer: **CSx**
* Pain * Mucupurulent/purulent discharge * Deep excavation in the corneal *(well-defined edge)* * Fluorescein positive * Perifocal/diffuse corneal oedema * Circumcorneal vascularisation * Secondary uveitis
29
Non-melting, deep corneal ulcer: **Treatment**
* Eliminate the cause * Medical therapy: Atropine; Abx; Vitamins * Surgery
30
Melting, deep corneal ulcer: **Pathogenesis**
Formation of **proteases** & **collagenases** from: * PTF leucocytes - Abnormal secretion * Destroyed corneal epithelium & fibroblasts * Bacteria *(Pseudomonas spp.)* Stroma becomes solved → Melting → Ulcer → Corneal perforation
31
Melting, deep corneal ulcer: **CSx**
* Severe pain (blepharospasm & photophobia) * Purulent discharge * Diffuse corneal oedema * Grey-white, gelatin-like material at the base of the ulcer * Hypopyon * *Secondary uveitis*
32
Melting, deep corneal ulcer: **Treatment**
* Emergency intervention * Elimination of the cause * Surgery: * Microsurgery + Enzyme elimination * Chemical coagulation - Jodine; Phenol ## Footnote **Medical therapy is contraindicated!**
33
Descmetocele: **Define**
Form of ulcer where the stroma has thinned so much, that the integrity of the eyeball is maintained only by the Descemet membrane
34
Descemetocele: **CSx**
* Black & shining * Mucopurulent discharge * Pain * Staining by fluorescein
35
Descemetocele: **Treatment**
* Emergency intervention * Eliminate the cause * Medical therapy is contraindicated * Surgery: Direct suturing of cornea
36
List the operative treatment techniques of deep corneal ulcers
1. Grid keratotomy 2. Pedicle conjunctival graft transposition 3. Free island conjunctival graft transplantation 4. Direct suturing of the cornea
37
_Supportive_ techniques in the therapy of deep corneal ulcers
* Third eyelid flap * Tarsoraffy *(subpalpebral drainage)* * Post-operative mediation: Atropine; Abx; NSAID * Physical protection of the eye
38
Special forms of ulcerative keratitis
* Multipunctional keratitis * Herpetic keratitis * Corneal sequestrum
39
Infectious bovine keratoconjunctivitis: **Aetiology** "Pink eye"
* *Moraxella bovis (via flies)* 1. Adheres to the cornea 2. Haemolysin, dermo-necrolysin & collagenase 3. Ulceration & necrosis of the cornea
40
Infectious bovine keratoconjunctivitis: **Summary** "Pink eye"
* Frequent disease * Deep, melting & necrotic ulcer
41
Infectious bovine keratoconjunctivitis: **CSx**
* Uni-/bilateral * More severe in summer & young animals * Pain & lacrimation * Central corneal ulcer * Diffuse, pinkish corneal opacity * Corneal vascularisaiton * Descemetocele, corneal perforation, phthitis
42
Infectious bovine keratoconjunctivitis: **Treatment**
* Separation of diseased animals using fly repellants * Sub conjunctival depocillin/tetracycline * IV sulphonamides * Tarsorraphy/third eyelid flap *(if severe)* * Subconjunctival steroids
43
Non-ulcerative keratitis: **Definition**
Inflammation of the superficial/ deeper layers of the cornea without ulcer formation * Uberreiter's syndrome * Pigmentary kereatitis * Endothelial syndrome
44
Überreiter's syndrome: **Synonyms**
* Chronic immune-mediated KCS * **Chronic superficial keratitis** * Pannus ## Footnote *Usually seen in German Shepherds*
45
Überreiter's syndrome: **Aetiology**
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
Überreiter's syndrome: **CSx**
* 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
What is shown?
Überreiter's syndrome: Third eyelid form
48
Überreiter's syndrome: **Treatment**
Cannot be cured * Medical management: * Subconjunctival & topical steroids * Topical cyclosporin * Surgical management: * Superficial keratectomy * Post-operative therapy
49
Trauma to the cornea: **Aetiology**
* Biting * Scratching * Kicking * Accident * Foreign body * Surgery
50
Trauma to the cornea: **CSx (superficial)**
* Loss of epithelium * Oedema * Pain
51
Trauma to the cornea: **CSx (Deep)**
* Deep gap in the stroma * Diffuse oedema * Opacity * Severe pain * Discharge Perforation/laceration?
52
Trauma to the cornea: **Perforation**
* Full thickness injury of the cornea with outflow of aqueous humor * Severe pain
53
Trauma to the cornea: **Perforation-laceration**
* Perforation together with widespread rupture * Prolapse of the iris-lens vitreous * Severe pain
54
Trauma to the cornea: **Treatment (Superficial & deep)**
Similar to ulcer therapy
55
Trauma to the cornea: **Treatment (perforation)**
* Surgical therapy * Conjunctival graft; Direct suturing

Ophthalmology (9 decks)

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