Equine Ophthalmology Flashcards
What 4 things does an equine ophthalmic examinatino require?
- sedation - detomidine/xylazine +/- butorphanol
- eyelid akinesia - nerve blocks
- mydriasis
- corneal anesthesia
What materials are required for eyelid akinesia? What blocks are used for motor and sensory innervation?
1-2 cc lidocaine, 25 g needle
MOTOR - auriculopalpebral (CN VII)
SENSORY - supraorbital (frontal nerve), lacrimal nerve
What is the normal result of a Schirmer tear test in horsrs?
> 20 mm/min
- not commonly done in equine species, as KCS is rare
What is the normal intraocular pressure of horses? Why is it commonly measured?
up to 30 mmHg
diagnose glaucoma, commonly caused by uveitis or immune disease
What is the purpose of fluorescein staining? How is it performed?
diagnose ulcers
place strip in the medial canthus that contains the lacrimal sac and hold the eye closed so the ulcer can take up the stain
How is a corneal scrape used? When is it utilized?
scrape the back of a scalpel blade against the cornea
only when necessary, to perform cytology
When must a corneal culture be performed? How is it performed?
prior to applying proparacaine
moisten the swab before sampling, then swab over the lesion only
What response is necessary for eyelid lacerations?What 3 things can improper management lead to?
surgical repair ASAP
- trichiasis
- exposure keratitis
- keratoconjunctivitis
What is required for proper evaluation of eyelid lacerations?
- complete ocular exam
- sedation
- local akinesia
+/- skull radiographs
How are eyelid laceration repairs performed? What 2 things must be avoided?
- 10% povidone solution antiseptic
- perform a figure 8 pattern beginning from the eyelid margin and inward with 4-0 or 5-0 suture (silk)
- scrub solutions - lytic to cornea
- removing seemingly redundant tissue (exposure keratitis)
What are 4 additional considerations that need to be addressed after eyelid laceration repairs?
- tetanus booster if more than 6 months from last vaccination
- antibiotics - ocular topicals*, systemic
- anti-inflammatories - Banamine
- protection of repair - masks
What are the 2 most common causes of equine infectious keratitis?
- trauma
- adnexal disease - entropion in foals, poorly healed eyelid lacerations
What are 4 unique characteristics associated with equine infectious keratitis compared to other species?
- follow up is more rigorous
- ulcers are more likely to become infected
- commonly rapidly progress to deep ulcerations
- uveitis is more severe in the horse
What are 3 aspects of treating superficial corneal ulcers? What progression should be seen?
- triple antibiotic TID
- atropine to effect (can cause ileus and compaction!)
- systemic Banamine or phenylbutazone
daily decrease in ulcer size
What should be done if the healing of superficial corneal ulcers ceases?
corneal scraping and culture
What are 6 indications of infection of ulcers?
- corneal edema
- stromal opacity
- stromal loss
- vascularization
- severe miosis
- hypopyon
What is mycotic keratitis? What are the 3 most common signs? What else is seen?
usually slowly progressing ulceration of the cornea caused by fungi
edema, stromal infiltrate, vascularization
- plaques
- keratomalacia —> liquefaction, dissolving
- secondary uveitis
What is a descemetocele? What is the characteristic appearance?
corneal ulcer resulting from the loss of stroma, causing the eye to become very fragile
deep divot with a clear center, where the walls take up the stain, but Descmet’s membrane will not
What is a collagenolytic ulcer? What are the 3 most common clinical signs?
melting ulcer caused by the degradation of PMNs and proteases released by bacteria or fungi
- pain
- white-yellow gelatinous ulcer able to take up fluorescein
- secondary anterior uveitis
What is the characteristic appearance of collagenolytic ulcers?
“puddle” looking protrusion beyond the corneal surface, where the stroma is gray and able to take up fluorescein
What is an indolent ulcer? What are the 2 most common treatment options?
ulcer formed when the squamous cells no longer adhere to the stroma
- debridement of the epithelium
- grid keratotomy - scratch the surface with a 25 g needle held tangentially to the corneal surface to drag healthy cells onto the ulcer
What is the most common cause of anterior uveitis?
secondary to corneal disease
- ERU = continual, chronic flare-ups
What is the hallmark sign of anterior uveitis? What else is commonly seen?
aqueous flare
- pain
- epiphora
- blepharospasm
- photophobia
- corneal edema
- miosis
- hyperemic conjunctiva
- hypopyon
What is equine recurrent uveitis (ERU)?
inflammation of the iris, ciliary body, choroid, and retina that recurs periodically with an unknown etiology
