Ophthomology Flashcards
What are some unique anatomical features of the equine eye?
Horizontal elliptical pupils, laterally positioned globes, corpora nigra, paurangiotic retinal vascular pattern, Stars of Winslow
What are some potentially requirements to perform an equine ophthalmic exam?
Restraint, sedation, topical anesthetic, nerve block
Which motor nerve do you block for an ophthalmic exam?
Auriculopalpebral nerve. Branch of CN VII
Where are the three points that the auricopalpebral nerve can be blocked?
- ) highest point of zygomatic arch
- ) caudal to bony process of frontal bone of zygomatic arch
- ) caudal to posterior ramus of mandible
What sensory nerve do you block for an equine ophthalmic exam?
Frontal (supraorbital) nerve block
What is the most common cause of blindness in horses? What is it called in laymen’s terms?
Equine recurrent uveitis (ERU). Moon blindness
T/F: There is only one cause for ERU.
False. There are many!
What is the pathogenesis of moon blindness in equine?
Invasion of antigen into eye -> deposition of Ag/Ab complexes -> continued presence of antigen (hence the recurrence)
T/F: The continued presence of live infectious organisms are needed for ERU disease
False. Just the antigen!
What are some clinical signs for active uveitis?
Aqueous flare, miosis, corneal edema, hyphema, hypopyon
What are some clinical signs for chronic uveitis?
Posterior synechia Iris hyperpigmentation Granula iridica atrophy Secondary cataracts Vitreal degeneration Retina edema and degeneration Retinal detachment
What are some lesions/scars you may witness in a fundus exam on a horse with chronic uveitis?
Chorioretinitis scar, bullet-hole scarring, butterfly lesions
How would you treat band keratopathy on a horse with chronic uveitis?
keratectomy or DBD
What signs of chronic uveitis can cause blindness?
Corneal edema, cataract, synechiation, 2ary glaucoma, retinal detachment
What are some work-ups you would want to perform to diagnose a horse with uveitis?
physical exam, deworm history, CBC, chem,
Titers: lepto, toxo, lyme, brucella
What are your treatment goals for horses with uveitis?
preserve vision, decrease pain, minimize any permanent damage, prevent recurrence, treat underlying cause (if possible)
What is a good systemic NSAID to use for a horse with uveitis?
Flunixin meglumine
What is a good systemic corticosteroid to use on a horse with uveitis?
Prednisolone, dex
What is a good systemic antibiotic to use on a horse with uveitis?
doxycycline
What mydriatic would you want to use for a horse with uveitis?
Atropine 1%
T/F: You want to treat equine uveitis very aggressively and for a long time.
True
What is a technique for giving cyclosporine into the equine eye to fight uveitis, and is effective for over 2 years?
Cyclosporine implants
T/F: Most horses with uveitis, no matter how good the treatment, will go blind
True
What does subpalpebral lavage (SPL) allow?
Safe drug administration, comfort, less medication wasted
T/F: SPL’s are very difficult to implant and need to be referred.
False. Easy peasy!
What disinfectant solution do you use to treat eyelid lacerations in horses? (Hint: It’s not chlorihex)
Diluted betadine solution (0.2%)
What are some clinical signs seen with corneal ulceration in the horse?
blepharospasm, epiphora, edema
What might cause a corneal ulcer in a horse to become keratomalacic?
Secondary bacterial or fungal infections, endogenous proteinases, iatrogenic steroid administration
What are factors of a corneal ulcer to assess when examining a horse with said condition?
The integrity of the globe, anterior chamber depth, depth of ulcer, neovascularization, infiltrates, reflex uveitis
How do you diagnose corneal ulceration in a horse?
Corneal cytology, corneal swab
How do you treat an acute, uncomplicated corneal erosion in a horse?
Topical broad spectrum antibiotics (TID), atropine 1% (BID), rechecks
How do you treat a complicated corneal ulcer in a horse?
Topical broad spectrum antibiotics (q 1-2 hrs), antifungals (q 6-8 hrs), topical antiproteinase therapy, atropine 1%, NSAIDs, subpalpebral lavage, eye cup
T/F: You cannot use topical steroids in a horse with corneal ulceration.
True!
How deep of the stromal should be ulcerated before considering surgical treatment?
50%
What is the surgical treatment for equine corneal ulceration?
conjunctival graft
What is a stromal abscess?
It is when there is a small puncture wound in the corneal that seals, but leaves an infection or FB inside.
What are some clinical signs seen with stromal abscesses?
Infiltrates, corneal edema, vascularization, reflex uveitis
T/F: You need to treat stromal abscesses aggressively.
True
What is the pathogenesis for eosinophilic keratitis in horses?
We don’t know!
What are some clinical signs seen with eosinophilic keratitis?
blepharospasm, conjunctival hyperemia, mucus discharge, white plaques, vascularization, superficial corneal ulceration, peripheral cornea
How do you diagnose eosinophilic keratitis?
corneal cytology
How do you treat eosinophilic keratitis?
topical corticosteroids, topical mast cell stabilizer (alomide), topical cyclosporine
T/F: the prognosis for eosinophilic keratitis in horses is usually very good.
True
What is the most common periocular and ocular tumor in horses?
ocular squamous cell carcinoma
T/F: Ocular SCC’s are common slow in metastasis, and do not recur often
False. They ARE slow in metastasis, but recurrence is common
What locations are most prone is ocular/periocular SCC in horses?
3rd eyelid medial canthus limbus lower eyelid cornea, conjunctiva, orbit
How do you medically treat SCC in horses?
immunotherapy and chemotherapy
Which surgical therapies are used for SCC in the equine eye?
3rd eyelid, enucleation, exenteration
What structures of the would affected with SCC would you perform cryotherapy?
Cornea, eyelid, 3rd eyelid
What structures of the eye affected with SCC would you perform brachytherapy?
Eyelid, conjunctiva
T/F: The smaller the lesion of SCC in the eye, the worse the prognosis.
False.
What are the three things you want to do with an equine with SCC?
Biopsy, aggressive treatment, and RECHECK!
