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Ophthalmology > Unit 2 - Equine Ophtho > Flashcards

Unit 2 - Equine Ophtho Flashcards

1
Q

Explain the visual field of horses.

A

Due to their lateral eye placement - total horizontal visual field (350 degrees), binocular visual field (60)

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2
Q

What are the unique parts of equine iris ocular anatomy?

A

Corpora nigra/Granula iridica

Pupil shape

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3
Q

What are the unique parts of fundus equine anatomy?

A

Paurangiotic retina

Stars of winslow

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4
Q

The main nourishment of the equine retina is via what?

A

The Starrs of Winslow

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5
Q

What type of vision does the horse have?

A

Dichromatic

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6
Q

What should be used to facilitate te equine eye exam?

A

Dark environment

Sedation

Nose twitch

Periocular nerve blocks

topical anesthesia

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7
Q

What are the components of the equine eye exam?

A

General distance exam

Cranial nerve testing

Ophthalmic diagnostics

Adnexa and globe exam

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8
Q

T/F: Fluoresceine staining should be performed for every horse eye exam.

A

True

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9
Q

When I say the fluoroscein stain was positive, what does that mean?

A

There is an ulcer - the fluorescein attaches to the stromal layer

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10
Q

Aside from looking for an ulcer, what is fluorescein stain good at testing for?

A

It simultaneously does the Jones test - tests nasolacrimal duct flushing (we want a positive test)

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11
Q

What is the normal IOP of the horse?

A

15-30 mmHg

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12
Q

Tonometry should be performed at what level in the horse?

A

At or above heart level

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13
Q

What are the preferred tonometry instruments for horses?

A

TonoVet or TonoVet+

Tonopen is not ideal

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14
Q

What does the auriculopalpebral block block?

A

Motor innervation to the orbicularis oculi

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15
Q

What sensory nerve blocks can be done in the horse?

A

Frontal/Supraorbital

Infratrochlear

Lacrimal

Zygomatic

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16
Q

What is the most common equine eye/adnexal tumor?

A

Squamous cell carcinoma

If you see a mass around the eye you should think SCC

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17
Q

What are the most common locations for SCC in the horses eye?

A

Eyelids, third eyelid, conjunctiva, and limbus/cornea

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18
Q

What are the predisposing factors for SCC?

A

Ultraviolet radiation

Lack of periocular pigmentation

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19
Q

How do SCC present?

A

Initially hyperemic area progressing to ulceration (lids) then to papillomatous and fleshy masses

Varying degrees of ulceration, necrosis, and inflammation

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20
Q

What is the therapeutic goal of SCC?

A

Destroy the tumor while preserving ocular function and cosmesis

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21
Q

What is the recommended treatment for SCC?

A

Surgical excision and adjunctive therapy - there are a lot of options

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22
Q

How often should a horse be reevaluated if they have had SCC removed?

A

Every 6months for life

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23
Q

Where can SCC locally invade? Metastasize?

A

Invade - soft tissue, boney orbit, sinuses, brain

Metastasize - LN, salivary glands, thorax

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24
Q

At what location do SCC have the highest recurrence rate?

A

Eyelid or third eyelid

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25
Q

What are the prevention strategies for SCC?

A

UV light protection mask

Eyelid tattooing

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26
Q

What is the usual cause of corneal ulceration?

A

Trauma

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27
Q

What are the keys to success of corneal ulcer management?

A

Diagnose early

Treat appropriately

Monitor closely

28
Q

What are the complicating factors for corneal ulceration management?

A

Infection

Melting

29
Q

What is important to aid in diagnosis of corneal ulcers?

A

Adequate restraint/sedation, nerve blocks, topical anesthesia

Examine for FB

Fluoresscein stain

30
Q

What should be done if there are infected, melting, or stromal defects on the eye?

A

Culture and sensitivity

Cytology

31
Q

What is the recommended therapy for simple ulcer management?

A

Topical broad spectrum antibiotic TID-QID - NO STERIOD

Atropine 1% ointment SID-BID then taper

Systemic Anti-inflammatory - Flunixin meglumine, phenylbutazone

32
Q

What side effect can atropine cause in horses?

A

Colic

33
Q

When should simple ulcers be rechecked in horses?

A

3-5 days

34
Q

What are the forms of complicated corneal ulcers?

A

Nonhealing

Infected

Melting

Deep or ruptured

35
Q

What are the infectious causes of complicated corneal ulcers?

A

Bacterial - Staphylococcus, Streptococcus, Corynebacterium, Pseudomonas

Fungi - Aspergillus, Fusarium

36
Q

It is difficult to give horses liquid medications constantly, what can be done to mitigate this and allow for the treatments?

A

Subpalpebral lavage line

37
Q

How are complicated corneal ulcers treated?

A

Topical antibiotic solutions - ciprofloxacin, ofloxacin, gentamicin, tobramycin, chloramphenicol, cefazolin

Oral NSAID BIDx3d then SID: Flunixin meglumine, phenylbutazone

Atropine

38
Q

What are the preferred antifungal medications for the treatment of complicated corneal ulcers?

A

Topical - Voriconazole, Itraconazole, silver sulfadiazine derm cream

Systemic - Fluconazole

39
Q

In addition to topical abx and anti-inflammatories, what else should be used to treat complicated corneal ulcers?

A

Antiproteinase/anticollagenase agents:

Serum/plasma q1-2h

EDTA

N-acetylcysteine

Tetracycline abx

+/-Systemic abx

40
Q

What are the monitoring recommendations for complicated corneal ulcers?

A

Hospitalize or recheck in <48 hours

Weekly therafter if improving

Referral if unchanged or worse

41
Q

What can be done to prevent self trauma in complicated corneal ulcer cases?

A

Eyesaver mask

42
Q

What surgical treatment can be done to treat complicated corneal ulcers?

A

Keratectomy or corneal debridement

Conjunctival +/- collagen graft

Corneoconjunctival transposition

Corneal and/or amniotic membrane transplantation

43
Q

What can cause deep corneal stromal abscesses?

A

Infectious agens get trapped within the cornea - either an infected ulcer that epithelializes rapidly or a small puncutre wound that seals

44
Q

What is the clinical appearance of deep corneal stromal abscesses?

A

Severe pain

Fluoresceine negative whiteish yellow stromal opacity

Corneal vascularization and edema

45
Q

What must you differentiate deep corneal stromal abscesses from?

A

Primary uveitis

46
Q

What medication should you not use in cases of primary uveitis?

A

Steroids

47
Q

How are deep corneal stromal abscesses treated/

A

Aggressive medical therapy +/- durgical intervention

48
Q

What is the recommended medical treatment for corneal stromal abscesses?

A

Antimicrobials for bacterial/fungal infection:

  • Topical ciprofloxacin and chloramphenicol q 3-6 hrs
  • Topical voriconazole q 3-6 hrs
  • Systemic fluconazole and SMZ-TMP if vascularized

Reflex uveitis treatment:

  • Atropine BID-QID (watch for colic signs!!!)
  • Banamine 1.1 mg/kg BID then slowly decrease
    • +/- Omeprazole prophylactic dose

Subpalpebral lavage line recommended

49
Q

What is the most common cause of equine blindness?

A

Uveitis

50
Q

What are the numerous causes of uveitis in horses?

A

Infectious diseases

Trauma

Neoplasia

Idiopathic/immune mediated

51
Q

What are the most common clinical signs associated with uveitis in horses?

A

Blepharospasm, epiphora, photophobia, conjunctival/episcleral blood vessel injection, aqueous flare, miosis

52
Q

What diagnostic tests should be done for uveitis?

A

Rule out primary corneal disease

CBC/Chemistry

Serology - Leptospira

53
Q

How is uveitis treated in horses?

A

Address the underlying cause

Treat eye aggressively then taper

54
Q

How long should uveitis be treated in horses?

A

2-4 weeks past resolution

55
Q

What topical medications can be used for uveitis therapy?

A

Anti-inflammatories QID+

  • Steroid: dexamethasone 0.1% or prednisolone acetate 1%
    • Do not use hydrocortisone – weak steroid and can’t penetrate cornea
    • FLUORESCEIN STAIN BEFORE USING STEROIDS!
  • NSAID: flurbiprofen 0.03% or diclofenac 0.1%

Atropine 1% SID-BID

  • Monitor for signs of colic, discontinue use if noted
56
Q

What systemic medications are used for uveitis treatment?

A

Oral anti-inflammatory treatment (NSAID)

  • Flunixin meglumine 1.1 mg/kg PO SID-BID
  • Phenylbutazone 1 g PO SID-BID (1000# horse)
  • Firocoxib (Equioxx®) 40 mg SID (1000# horse)?
  • Aspirin 25 mg/kg PO SID-BID for maintenance treatment?
57
Q

What is equine recurrent uveitis also known as?

A

Moon blindness or periodic ophthalmia

58
Q

What breeds are predisposed to ERU?

A

Appaloosa and draft breeds

59
Q

T/F: ERU is immune-mediated following the trigger

A

True

60
Q

What are the stages of ERU?

A

Acute, insidious, or chronic end-stage

61
Q

What complicating issues are associated with ERU?

A

Calcific band keratopathy

Blinding cataract

Vitreal floaters or fibrinous traction bands

Retinal detachments

Secondary glaucoma

62
Q

What are the goals for ERU treatment?

A

Preserve vision, decrease pain, prevent or minimize recurrence

63
Q

How is ERU treated?

A

Topical and systemic uveitis treatment -Anti-inflammatories and atropine as noted before

Systemic antibiotics - Streptomycin, penicillin, tetra/doxycycline, enrofloxacin

Intravitreal injection - 4 mg preservative-free gentamicin

Surgical treatment- Vitrectomy, Suprachoroidal cyclosporine implant

64
Q

What is the prognosis of ERU?

A

POOR

65
Q

What are the components of the pre-purchase examination?

A

Vision and PLRs

Anterior segment exam

Lens and posterior segment exam

Note: Make sure to cite and discuss all findings

Ophthalmology (13 decks)

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