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Equine Med & Surgery > Ophtho > Flashcards

Ophtho Flashcards

1
Q

Why do horses have high amounts of ocular trauma?

A
  • prominent location of eyes
  • propesity for horses to throw their heads
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2
Q

most common ocular disease in horses

A

corneal ulcers

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3
Q

corneal ulcers are almost always caused by ______

A

trauma

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4
Q

How are corneal ulcers diagnosed?

A

fluorescein dye-binds to stroma

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5
Q

complicated corneal ulcers:

A
  • do not heal in 3-7 days
  • have a collagenase component
  • mechanical obstruction to healing
  • infected
  • danger of perforation-ulceration into anterior chamber
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6
Q

Clinical features of complicated corneal ulcers

A
  • obvious corneal defect
  • white/yellow cellular infiltrate
  • surrounding corneal edema
  • secondary uveitis
  • +/- chronic
  • +/- pain
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7
Q

What should you do any time you have a complicated corneal ulcer?

A

CULTURE-aerobic & fungal

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8
Q

Where should you obtain the sample for culture of a corneal ulcer?

A
  • margin of ulcer
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9
Q

When is corneal cytology indicated?

A

any cornea with cellular infiltrate

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10
Q

What is a topical anesthetic used in ophtho?

A

proparacaine

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11
Q

Presence of _____ in the scraping ensures adequate sample for cytology

A

epithelial cells

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12
Q

concerns if PMNs are the main cell type found in corneal cytology

A

bacterial or fungal infection

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13
Q

concerns if lymphocytes/plasma cells are main cell present in corneal cytology

A

immune-mediated process

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14
Q

What are your concerns if eosinophils dominate the corneal cytology?

A

parasitic or eosinophilic keratitis

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15
Q

Superficial ulcers with a redundant epithelial border, minimal corneal neovascularization, focal edema, no cellular infiltrate or signs of infection

A

indolent corneal ulcers

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16
Q

Pathogenesis of indolent corneal ulcers

A
  • routine corneal ulcer
  • basal epithelial cells migrate to cover wound but cannot attach to underlying stroma
  • minor trauma results in repeat ulceration
  • likely superficial stromal defect
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17
Q

Indolent ulcer treatment

A
  • debridement-remove any loose epithelium
    • standing keratectomy
    • diamond burr keratectomy-doesnt leave scar
  • oxytetracycline (Terramycin) BID-TID-decreases matrix metalloproteinases and promotes epithelialization
  • oral doxy?
  • topical serum-anticollagenase, growth factors
  • equine contact lens-efficacy unknown
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18
Q

Most common agent isolated from infected corneal ulcers

A

Pseudomonas

also Streptococcus

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19
Q

Clinical signs of “melting” corneal ulcers

A
  • white-yellow cellular infiltrate
  • corneal edema
  • increasing ocular inflammation
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20
Q

Serum contains _________, a very effective anticollagenase

A

alpha-2 antiglobulin

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21
Q

What are some topical anticollagenase medications?

A
  • serum
  • acetylcysteine
  • EDTA
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22
Q

What is a non-topical medication that has anticollagenase properties?

A

doxycycline

23
Q

Characteristics of Moxifloxacin

A
  • 4th generation fluorinated quinolone
  • less ocular toxicity
  • better penetration
  • better bacterial coverage – esp. Staph, Strep
24
Q

Surgical procedures that may be indicated for an infected corneal ulcer

A
  • keratectomy
  • conjunctival flap or amnion membrane
25
Q

What is the purpose of corneal cross-linking?

A

stabilize melting corneas

26
Q

How is corneal cross linking performed?

A

Instill riboflavin eye drops q2 min. for 25 minutes then treat cornea with UV light for 30 minutes

27
Q

What is the most common fungal agent involved in corneal ulcers?

A

Aspergillus

28
Q

Topical corticosteroids may predispose to what?

A

fungal keratitis

29
Q

When are fungal infections more common in the northern US?

A

summer

30
Q

When are fungal infections more comon in the southern US?

A

winter

31
Q

Typical history with fungal keratitis

A

ulcer present for 7-14 days and now getting worse

32
Q

Diagnostic options for fungal keratitis

A
  • cytology
  • histology of corneal biopsy
  • culture
  • PCR for DNA
33
Q

Treatment plan for mycotic corneal ulcers

A
  • effective debridement or superficial keratectomy +/-conjunctival flap-reduce organism&inflammatory debris
  • topical antifungals
  • systemic antifungals
  • topical & systemic antibacterials-(since commonly co-infected with bacteria)
  • uveitis control-uveitis usually the cause of ocular loss and blindness
34
Q

Voriconazole is effective against__________

A

filamentous fungi

35
Q

What is the role of atropine administration in the treatment of fungal keratitis?

A

uveitis

36
Q

most common cuase of blindness in horses

A

recurrent uveitis

37
Q

Components of the uveal tract

A
  • iris
  • ciliary body
  • choroid
38
Q

anterior uveitis

A

inflammation of the iris and ciliary body

39
Q

posterior uveitis

A

inflammation of the choroid and retina

40
Q

pan-uveitis

A

inflammation of the entire uveal tract (most common)

41
Q

Three important questions about suspect uveitis cases

A
  1. does horse have signs of active or quiescent (chronic) uveitis?
  2. is the uveitis acute, chronic, or recurrent?
  3. is the uveitis primary (endogenous) or secondary to an ocular are systemic abnormality?
42
Q

Signs of active uveitis

A
  • aqueous flare/hypopyon
  • miosis
  • hypotony
  • photophobia
  • pain/blepharospasm
  • vitreous debris
  • mild corneal edema
  • hyphema
  • decreased vision
43
Q

Corneal edema is a sign of what type of uveitis?

A

chronic

44
Q

What is the most common cause of cataract formation in horses?

A

chronic uveitis

45
Q

Ophthalmic causes of uveitis

A
  • corneal disease
  • neoplasia
  • trauma
46
Q

what is the underlying cause of equine recurrent uveitis?

A

immun-mediated

47
Q

Three recognized clinical types of equine recurrent uveitis

A
  1. classic recurrent “anterior” uveitis
  2. persistent “subclinical” uveitis
  3. primary posterior uveitis
48
Q

What form of recurrent uveitis is most common?

A

“classic” anterior uveitis

49
Q

What breeds have increased incidence of subclinical uveitis?

A
  • Appaloosa-up to 25%
  • Draft breeds
50
Q

Primary posterior uveitis is most common in what breed?

A

warmbloods

51
Q

Poor prognostic indicators for long-term vision with uveitis

A
  • Appaloosa
  • elevated IOP
  • positive leptospiral titer (serum or AH); especially C>4
52
Q

What are two steroids that will penetrate the eye well?

A

Pred acetate

dexamethasone HCl

53
Q

What is a consideration of using atropine HCl in terms of possible negative side effects?

A

decreased gut motility-predispose to colic

54
Q

Cyclosporine implants may be indicated in horses that meet what criteria?

A
  • ERU greater than three months duration
  • uveitis controlled medically
  • have frequene recurrence
  • are still visual

Equine Med & Surgery (11 decks)

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