Ophthalmology Flashcards
Describe the anatomy of the ruminant eye
Complete bony orbital rim, monocular vision, cornea is elongated horizontally, pupil is oval in horizontal plane
Describe an auriculopalpebral nerve block
Motor block (no anesthesia), use 1-2% lidocaine 5-7cm caudal to zygomatic process where nerve crosses zygomatic arch
What are the congenital diseases of the orbit?
Anophthalmia, microphthalmia, cyclopia (sheep)
Describe microphthalmia
Often combined with other defects, unilateral or bilateral, can be caused by teratogen exposure (selenium/sulfate in sheep) viral disease (blue tongue- sheep, BVDV- cattle), is heritable in Guernseys, Herefords, and Shorthorns
What causes cyclopia in sheep?
Maternal ingestion of veratum californicum at day 14 in utero
What are causes of exophthalmos in ruminants?
Retrobulbar mass (infection or LSA), glaucoma
How are retrobulbar masses treated?
Euthanasia or debulk mass and treat underlying infection
Which ruminants are predisposed to entropion?
Sheep
How is entropion treated?
Temporary tacking, injectable solutions, Holtz-Celsus procedure
What is a corneal dermoid?
Benign congenital tumor of haired skin on the cornea, relatively rare, most common in Herefords
Describe the etiology of infectious bovine keratoconjunctivitis
Moraxella bovis (gram negative bacillus) adheres to corneal surface with capsular pili, moraxella ovis and boviculi invade secondarily
How is infectious bovine keratoconjunctivitis transmitted
Introduction of new animal, face flies spread infection, may occur with concurrent infections, predisposed by UV light and non-pigmented skin around the eyes
What are the clinical signs of infectious bovine keratoconjunctivitis?
Central corneal ulcer with edema, cellular infiltrate, vascularization, perforation, fibrosis, conjunctivitis, epiphora, blepharospasm, mucopurulent discharge, photophobia, miosis
How is infectious bovine keratoconjunctivitis diagnosed?
Clinical signs, can swab and culture
How is infectious bovine keratoconjunctivitis treated?
Oxytetracycline or tulathromycin, subconjunctival injections of penicillin, protect cornea with temporary tarsorrhaphy
What is the treatment for IBK if corneal perforation occured?
Enucleation
How is infectious bovine keratoconjunctivitis prevented?
Fly control, segregate affected animals, decrease eye irritation, provide shade, vaccine available (questionable)
What is infectious keratoconjunctivitis called in goats and sheep?
Pink eye, heather blindness, blight
What are the bacterial agents that infect infectious keratoconjunctivitis in goats and sheep?
Chlamydophila spp., Mycoplasma spp.
How is infectious keratoconjunctivitis treated in goats and sheep?
Oxytetracycline (systemic or topical)
What is the causative agent of malignant catarrhal fever?
Ovine herpesvirus 2
What are the clinical signs of malignant catarrhal fever?
Severe vasculitis (hematuria, peripheral corneal edema, bloody diarrhea, oral ulcers), fever, lymphadenopathy, respiratory disease, death
What type of cancer do ruminants get in their eye?
Squamous cell carcinoma
What are the predisposing factors for SCC of the eye?
Age, increased hours of sunlight, decreased pigmentation around the eye
What are the clinical signs of eye SCC?
Bulbar conjunctiva and cornea usually affected, progresses with small white to pink mass that becomes necrotic and irregular
What is a precursor to carcinoma of eyelids?
Keratosis
Describe the neoplastic behavior of eye SCC
Locally aggressive, metastasize later in disease to orbital bones, maxilla, submandibular LNs, liver, lungs, pleura, kidneys, LNs
How is eye neoplasia diagnosed?
Clinical signs, biopsy and histopathology (not usually necessary)
How is eye neoplasia treated?
Curative or debulking surgery, enucleation if in multiple locations within eye, salvage if metastasized
Describe the four point block
Curved 3in spinal needle inserted through lids at dorsomedial, ventromedial, ventrolateral, and dorsolateral aspects of the eye, 10mL lidocaine injected at each location
Describe the Peterson nerve block
10-15mLs 2% lidocaine injected at the notch between zygomatic arch and supraorbital, numbs CNs II, III, IV, V, VI, can cause death
Describe removal of the third eyelid
Has minimal impact on tear production
Perform local anesthesia or four-point block, grasp lid with hemostats to expose base, clamp with large curved hemostats, remove lid with mayo scissors
What are indications for enucleation?
Extensive SCC, trauma, ruptured cornea due to pinkeye
Describe exenteration
Block the eye, close the lids, dissect intraocular muscles, clamp and ligate optic nerve and vessels or cut and suture lids closed as quickly as possible (simple interrupted, 1 layer closure), apply pressure bandage for 24 hours, antibiotics for 3-5 days, NSAIDs for 2-3 days, remove sutures in 2 weeks, control flies
What is hypopyon associated with?
Sepsis and FPT in calves
