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Small Animal Medicine II > Ophthalmology - Cornea > Flashcards

Ophthalmology - Cornea Flashcards

1
Q

What are the features of the cornea that cause it to stay clear?

A
  • avascular
  • non-myelinated nerves
  • dehydrated
  • ordered cell arrangement
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2
Q

Describe how epithelial ulcers heal

A
  • hemidesmosomes degrade and disappear
  • rapid cell division at the limbus
  • epithelium slides to cover the ulcer
  • epithelium becomes fixed to the stroma as hemidesmosomes form again
  • takes about 7 days
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3
Q

Describe how stromal ulcers heal

A
  • stromal cells transform into contractile cells
  • these cells fill the defect
  • epithelialization occurs over the new stroma
  • stromal contracture causes disorganization of collagen, resulting in a scar
  • takes days to weeks
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4
Q

What is a facet?

A
  • a non-staining depression in the cornea

- forms when epithelialization occurs before the stroma becomes leveled

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5
Q

Describe how descemetoceles heal

A
  • vascular ingrowth needed first to provide scaffold for cell growth
  • eventually a scar forms
  • takes a long time
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6
Q

What is indicated by blue corneal opacity?

A

edema

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7
Q

What are the causes of corneal edema?

A
  • epithelial barrier disruption (allows tear film entry into stroma)
  • endothelial barrier/pump disruption (allows aqueous humor entry)
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8
Q

What is indicated by red corneal opacity?

A

corneal neovascularization

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9
Q

What are the causes of corneal neovascularization?

A
  • superficial vessels (granulation tissue or ghost vessels)

- deep vessels (ciliary flush)

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10
Q

When does superficial neovascularization occur?

A

occurs with superficial stimuli

- KCS, eyelid/hair abnormalities, superficial corneal ulcers

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11
Q

Describe the appearance of superficial neovascularization

A
  • branching tree-like structure

- can be seen crossing the limbus

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12
Q

When does deep neovascularization occur?

A

occurs with deep stimuli

- uveitis, glaucoma, deep corneal inflammation/ulceration

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13
Q

Describe the appearance of deep neovascularization

A
  • “hedge row”
  • “crown of thorns”
  • vessels cannot be seen crossing the limbus
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14
Q

What is indicated by white corneal opacity with a yellow or green hue?

A

white blood cell infiltration

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15
Q

What is indicated by white corneal opacity with gray or wispy features?

A

fibrosis

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16
Q

What is indicated by crystalline or chalky white corneal opacity?

A

mineral or lipid

17
Q

Describe the features of corneal WBC infiltration

A
  • often very painful
  • associated with severe corneal disease or uveitis
  • signals corneal infection
18
Q

Describe the features of corneal fibrosis

A
  • scar from previous keratitis
  • dull white
  • non-painful
  • involves contracture of lamellar stromal collagen
19
Q

What are the possible causes of mineral or lipid deposits in the cornea?

A
  • corneal dystrophy (lipid)

- corneal degeneration (lipid or mineral)

20
Q

What are the causes of brown corneal opacity?

A
  • epithelial pigment (canine pigmentary keratitis)

- endothelial pigment (deflated uveal cysts, anterior synechia)

21
Q

What is the cause of black corneal opacity?

A

feline corneal sequestrum

- often due to FHV-1

22
Q

What is indicated by tan or greasy punctate?

A

keratic precipitates

  • cellular and fibrinous adhesions to the endothelial surface
  • due to uveitis
23
Q

What is the limbus?

A

junction between cornea and sclera

24
Q

What is ciliar flush?

A

360 degrees of deep corneal neovascularization

25
Q

What are the brachycephalic risk factors for ulcerative keratitis?

A
  • ocular prominence
  • decreased corneal sensitivity
  • adnexal abnormalities
  • tear film abnormalities
26
Q

What are the features of an uncomplicated/simple corneal ulcer?

A
  • a superficial corneal ulcer that heals in 7 days or less

- crisp, sharp edges of ulcer margin

27
Q

Describe the features of an indolent ulcer

A
  • will not heal due to lack of epithelial adherence to stroma
  • irregular, loose flaps of epithelium surrounding ulcer edge
  • staining pattern: “halo” under/around ulcer margin
28
Q

How is an indolent ulcer treated?

A
  • debride epithelium
  • if not healed: anterior stromal puncture or diamond burr debridement
  • topical antibiotics and analgesics
29
Q

What is the most common cause of melting ulcers?

A

Pseudomonas aeruginosa

30
Q

What are the feature of a deep stromal corneal ulcer?

A
  • inappropriate level of reflex uveitis
  • severe corneal edema
  • white blood cell infiltration
  • deep corneal vessels and episcleral injection
  • visible stromal loss or disruption
  • malacia
31
Q

What are the features of corneal perforation?

A
  • positive Seidel test
  • wrinkled corneal appearance
  • shallow anterior chamber
  • iris prolapse
  • fibrin plug
  • hyphema
32
Q

When is surgery recommended for stromal ulcers?

A

> 50% stromal loss or severe infection

descemetocele or perforation

33
Q

What surgery is done to correct stromal ulcers?

A
  • conjunctival pedicle flap

- 360 degree conjunctival graft

34
Q

What are the medical treatments for stromal ulcers?

A
  • topical antibiotics (cephalosporins, fluoroquinolones)
  • anti-collagenase therapy for melting ulcers (EDTA)
  • topical atropine and systemic NSAID/tramadol
35
Q

When are parenteral antibiotics indicated for stromal ulcers?

A
  • the ulcer has become vascularized
  • the cornea is close to perforation or has perforated
  • iatrogenic vascularization
36
Q

What is reflex uveitis?

A

the trigeminal nerve and certain cytokines cause direct stimulation of the ciliary body, inducing spasm, pain, and disruption of the blood ocular barrier

37
Q

What is a descemetocele?

A

a corneal ulcer that has reached the depth of descemets membrane

38
Q

What is keratomalacia?

A

softening of the cornea due to collagenolysis form infection and the ocular inflammatory response

39
Q

What is collagenolysis?

A

enzymatic destruction of the corneal stroma that signals infection

Small Animal Medicine II (15 decks)

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