Unit 2 - Equine Ophtho Flashcards
Explain the visual field of horses.
Due to their lateral eye placement - total horizontal visual field (350 degrees), binocular visual field (60)
What are the unique parts of equine iris ocular anatomy?
Corpora nigra/Granula iridica
Pupil shape
What are the unique parts of fundus equine anatomy?
Paurangiotic retina
Stars of winslow
The main nourishment of the equine retina is via what?
The Starrs of Winslow
What type of vision does the horse have?
Dichromatic
What should be used to facilitate te equine eye exam?
Dark environment
Sedation
Nose twitch
Periocular nerve blocks
topical anesthesia
What are the components of the equine eye exam?
General distance exam
Cranial nerve testing
Ophthalmic diagnostics
Adnexa and globe exam
T/F: Fluoresceine staining should be performed for every horse eye exam.
True
When I say the fluoroscein stain was positive, what does that mean?
There is an ulcer - the fluorescein attaches to the stromal layer
Aside from looking for an ulcer, what is fluorescein stain good at testing for?
It simultaneously does the Jones test - tests nasolacrimal duct flushing (we want a positive test)
What is the normal IOP of the horse?
15-30 mmHg
Tonometry should be performed at what level in the horse?
At or above heart level
What are the preferred tonometry instruments for horses?
TonoVet or TonoVet+
Tonopen is not ideal
What does the auriculopalpebral block block?
Motor innervation to the orbicularis oculi
What sensory nerve blocks can be done in the horse?
Frontal/Supraorbital
Infratrochlear
Lacrimal
Zygomatic
What is the most common equine eye/adnexal tumor?
Squamous cell carcinoma
If you see a mass around the eye you should think SCC
What are the most common locations for SCC in the horses eye?
Eyelids, third eyelid, conjunctiva, and limbus/cornea
What are the predisposing factors for SCC?
Ultraviolet radiation
Lack of periocular pigmentation
How do SCC present?
Initially hyperemic area progressing to ulceration (lids) then to papillomatous and fleshy masses
Varying degrees of ulceration, necrosis, and inflammation
What is the therapeutic goal of SCC?
Destroy the tumor while preserving ocular function and cosmesis
What is the recommended treatment for SCC?
Surgical excision and adjunctive therapy - there are a lot of options
How often should a horse be reevaluated if they have had SCC removed?
Every 6months for life
Where can SCC locally invade? Metastasize?
Invade - soft tissue, boney orbit, sinuses, brain
Metastasize - LN, salivary glands, thorax
At what location do SCC have the highest recurrence rate?
Eyelid or third eyelid
What are the prevention strategies for SCC?
UV light protection mask
Eyelid tattooing
What is the usual cause of corneal ulceration?
Trauma
What are the keys to success of corneal ulcer management?
Diagnose early
Treat appropriately
Monitor closely
What are the complicating factors for corneal ulceration management?
Infection
Melting
What is important to aid in diagnosis of corneal ulcers?
Adequate restraint/sedation, nerve blocks, topical anesthesia
Examine for FB
Fluoresscein stain
What should be done if there are infected, melting, or stromal defects on the eye?
Culture and sensitivity
Cytology
What is the recommended therapy for simple ulcer management?
Topical broad spectrum antibiotic TID-QID - NO STERIOD
Atropine 1% ointment SID-BID then taper
Systemic Anti-inflammatory - Flunixin meglumine, phenylbutazone
What side effect can atropine cause in horses?
Colic
When should simple ulcers be rechecked in horses?
3-5 days
What are the forms of complicated corneal ulcers?
Nonhealing
Infected
Melting
Deep or ruptured
What are the infectious causes of complicated corneal ulcers?
Bacterial - Staphylococcus, Streptococcus, Corynebacterium, Pseudomonas
Fungi - Aspergillus, Fusarium
It is difficult to give horses liquid medications constantly, what can be done to mitigate this and allow for the treatments?
Subpalpebral lavage line
How are complicated corneal ulcers treated?
Topical antibiotic solutions - ciprofloxacin, ofloxacin, gentamicin, tobramycin, chloramphenicol, cefazolin
Oral NSAID BIDx3d then SID: Flunixin meglumine, phenylbutazone
Atropine
What are the preferred antifungal medications for the treatment of complicated corneal ulcers?
Topical - Voriconazole, Itraconazole, silver sulfadiazine derm cream
Systemic - Fluconazole
In addition to topical abx and anti-inflammatories, what else should be used to treat complicated corneal ulcers?
Antiproteinase/anticollagenase agents:
Serum/plasma q1-2h
EDTA
N-acetylcysteine
Tetracycline abx
+/-Systemic abx
What are the monitoring recommendations for complicated corneal ulcers?
Hospitalize or recheck in <48 hours
Weekly therafter if improving
Referral if unchanged or worse
What can be done to prevent self trauma in complicated corneal ulcer cases?
Eyesaver mask
What surgical treatment can be done to treat complicated corneal ulcers?
Keratectomy or corneal debridement
Conjunctival +/- collagen graft
Corneoconjunctival transposition
Corneal and/or amniotic membrane transplantation
What can cause deep corneal stromal abscesses?
Infectious agens get trapped within the cornea - either an infected ulcer that epithelializes rapidly or a small puncutre wound that seals
What is the clinical appearance of deep corneal stromal abscesses?
Severe pain
Fluoresceine negative whiteish yellow stromal opacity
Corneal vascularization and edema
What must you differentiate deep corneal stromal abscesses from?
Primary uveitis
What medication should you not use in cases of primary uveitis?
Steroids
How are deep corneal stromal abscesses treated/
Aggressive medical therapy +/- durgical intervention
What is the recommended medical treatment for corneal stromal abscesses?
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
What is the most common cause of equine blindness?
Uveitis
What are the numerous causes of uveitis in horses?
Infectious diseases
Trauma
Neoplasia
Idiopathic/immune mediated
What are the most common clinical signs associated with uveitis in horses?
Blepharospasm, epiphora, photophobia, conjunctival/episcleral blood vessel injection, aqueous flare, miosis
What diagnostic tests should be done for uveitis?
Rule out primary corneal disease
CBC/Chemistry
Serology - Leptospira
How is uveitis treated in horses?
Address the underlying cause
Treat eye aggressively then taper
How long should uveitis be treated in horses?
2-4 weeks past resolution
What topical medications can be used for uveitis therapy?
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
What systemic medications are used for uveitis treatment?
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?
What is equine recurrent uveitis also known as?
Moon blindness or periodic ophthalmia
What breeds are predisposed to ERU?
Appaloosa and draft breeds
T/F: ERU is immune-mediated following the trigger
True
What are the stages of ERU?
Acute, insidious, or chronic end-stage
What complicating issues are associated with ERU?
Calcific band keratopathy
Blinding cataract
Vitreal floaters or fibrinous traction bands
Retinal detachments
Secondary glaucoma
What are the goals for ERU treatment?
Preserve vision, decrease pain, prevent or minimize recurrence
How is ERU treated?
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
What is the prognosis of ERU?
POOR
What are the components of the pre-purchase examination?
Vision and PLRs
Anterior segment exam
Lens and posterior segment exam
Note: Make sure to cite and discuss all findings
