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Describe conjunctival anatomy.
- mobile, elastic mucous membrane
- Palpebral: lines eyelids
- Bulbar: lines exposed surfaces of globe
- Fornix: cul-de-sac formed by reflections of conjunctiva at transition from lid to globe
- Nictitans: covered palpebral and bulbar surfaces of nictitating membrane
What are the 3 places where the conjunctiva is firmly attached?
- tarsal plate of eyelid margin
- nictitans leading edge (cartilage)
Describe the histology of the conjunctiva.
- non-keratinized stratified squamous epithelium with goblet cells between epithelial cells
- substantia propria= loose connective tissue, fenestrated capillaries, lymphoid tissues
- Subconjunctival space= potential space
What are the functions of the conjunctiva? (5)
- allows smooth gliding of NM and lids over globe
- immune protection for ocular surface
- leaky barriers allow movement of antibodies, inflammatory cells, etc to surface
- mucus layer of tear film produced by goblet cells
- mobile blood supply
What is the normal conjunctival flora?
- mostly gram + (staph and strep)
- small quantities of gram - and occasional fungal (E. coli, Pseud, Acinetobacter)
What are some congenital diseases of the conjunctiva? (2)
- dermoid: ectopic island of skin
- eyelid agenesis: failure of formation of portion of eyelid margin (cats- upper lid)
What are clinical signs of conjunctivitis? (4)
hyperemis, chemosis (swelling), follicles, ocular d/c
How can you differentiate conjunctival hyperemia versus episcleral hyperemia? (2)
- Epinephrine drop with blanch conjunctival vessels rapidly, but not episcleral vessels
- if you rub a Q-tip across the eye, conjunctival vessels will move with it, but episcleral vessels will not move
- conj vessels are tortuous; episcleral vessels are straight
What diagnostics should you pursue with conjunctivitis cases? (3)
- Cytology is indicated in ALL SPECIES
- Culture is only indicated with cats, sometimes food animals, almost never is dogs or horses
- IFA, PCR, VI rarely
What are the most common causes of canine conjunctivitis? (5)
- keratoconjunctivitis sicca!!!!!!!
- follicular conjunctivitis
- allergic/ atopy
- drug sensitivity
- non-specific response to illness
- [primary bacterial infection is so so rare]
Always do a(n) ____________ for any dog with red eyes/ conjunctivitis.
Schirmer tear test (b/c KCS is so common in dogs)
What is follicular conjunctivitis in dogs? (3)
- can be due to immune-mediated causes or environmental irritants
- common in young large breed dogs
- clinical signs include large lymphoid follicles, hyperemia, and mucoid d/c
What is the treatment for follicular conjunctivitis in dogs?
- topical dexamethasone TID then tapered
- topical cyclosporine good for repeated episodes
What are clinical signs of allergic conjunctivitis in dogs? (6)
- seasonal signs
- pruritus +/- follicles and d/c
- +/- concurrent blepharitis
- +/- periocular alopecia
How is allergic conjunctivitis diagnosed in dogs? (2)
- clinical signs
- cytology shows eosinophils and neutrophils
How is allergic conjunctivitis treated in dogs?
- topical corticosteroids (dexamethasone)
- treat underlying allergies (antihistamines, ASIT, etc etc)
Conjunctivitis in dogs is usually NOT ___________; whereas, in cats, it almost always is.
What are common causes of feline conjunctivitis? (5)
- Herpesvirus (esp if there is corneal involvement)
- eosinophilic keratoconjunctivitis
How is FHV-1-associated conjunctivitis treated? (3)
- L-lysine for the rest of life
- repeat course of famcyclovir for at least 2 weeks post-resolution
- stress management/ avoidance
What are clinical signs of the less common Chlamydial conjunctivitis in cats? (4)
chemosis, usually bilateral, mucopurulent d/c, +/- pseudomembrane (chunk of mucus that adheres to conjunctival surface)
How do you diagnose chlamydial conjunctivitis in cats?
cytology- inclusion bodies in epithelial cells 7-14 days post infection (may not see if early in infection)
How do you treat chlamydial conjunctivitis in cats? (2)
- oxytet or chloramphenicol ointment TID
- oral doxycycline for 3 weeks
What is a concern with chlamydial conjunctivitis in cats?
zoonotic potential!!! causes pinkeye in humans
Describe clinical signs of calicivirus in cats. (2)
- mild to moderate conjunctivitis
- oral mucosal ulcers (unique to this disease)
How do you treat calicivirus in cats?
supportive (disease is self-limiting)
What are clinical signs of mycoplasma conjunctivitis in cats? (4)
- usually unilateral
- mild hyperemia
- serous to mucopurulent d/c
How do you diagnose mycoplasma in cats? (2)
- clinical signs
- cytology (coccoid clusters on epithelial cell wall)
How do you treat mycoplasma in cats?
oxytet or chloramphenicol topically or oral doxycycline
How is eosinophilic keratoconjunctivitis treated in cats? (3 options)
- topical cyclosporin A BID, may try to discontinue after 2-3 months
- megesterol acetate, 4-5 days
- topical corticosteriods, may discontinue after 4-6 weeks
Causes of equine conjunctivitis. (8)
fly strike, seasonal allergies, dust, parasitic, equine recurrent uveitis, chronic nasolacrimal obstruction, eosinophilic keratoconjunctivitis, bacterial
What are causes of bovine conjunctivitis? (3)
- IBR (herpesvirus)
- infectious bovine keratoconjunctivitis (moraxella bovis)
What are clinical signs of bovine conjunctivitis cause by IBR? (4)
hyperemia, chemosis, serous to mucopurulent d/c, +/- peripheral corneal edema/ ulceration
How do you treat IBR conjunctivitis in cows?
symptomatic txt +/- topical antibiotics
What are clinical signs of IBK due to moraxella bovis in cows? (5)
epiphora, blepharospasm, photophobia, conjunctival hyperemia and chemosis, central corneal ulceration/ abscess
How do you treat moraxella bovis? (5)
- IM oxytet
- florfenicol (nuflor)
- tulathromycin (draxxin)
- tilmycosin (micotil)
- prevent with fly control
What are causes of ovine and caprine conjunctivitis? Treatment?
- mycoplasma (conjunctival hyperemia and chemosis, keratitis with vascularization of cornea)
- txt: IM oxytet
What is conjunctival worm that affects horses, cattle, sheep, dogs, and cats? Describe it.
- lives in conjunctival fornix, can live in nasolaccrimal system
- can see them cross the cornea
How do you treat conjunctival worms (Thelazia)? (1)
What is the conjunctival parasite that affects horses only? What does it cause?
- conjunctivitis and uveitis, depigmentation, +/- hypertrophy of conjunctiva and limbus
- Dx by conjunctival biopsy
How do you treat onchocera in horses? (2)
systemic NSAIDS, ivermectin
What are neoplasias that occur in the conjunctiva? (6)
- mast cell tumor
What portion of the third eyelid is usually pigmented?
What ist he major supportive structure of the third eyelid?
What are the glandular structures of the third eyelid? (2)
- lacrimal gland at the base (GNM- gland of the nictitating membrane)- produces aqueous portion of tear film
- covered in goblet cells- produces mucus portion of tear film
The nictitating membrane moves...
dorsolaterally (except birds- ventrolaterally) when the globe is retracted.
How do you examine the third eyelid?
- retropulse the globe (gently push globe back into orbit)
- use topical anesthetic and forceps to grasp leading edge to look at the back of the NM (r/o FB, look for lymphoid follicles)
What are diseases of the nictitians? (4)
- scrolled cartilage
- prolapsed gland of the nictitiating membrane (cherry eye)
- inflammatory diseases (follicles, plasmoma)
What is scrolled cartilage?
- vertical portion of the T-cartilage is kinked, preventing normal conformation to corneal curvature--> decreased spread of tear film
- tops of horizontal potion curl outward secondarily
How do you repair scrolled cartilage? (2 options)
- incision through conjunctiva over vertical cartilage--> imbricate edges--> 2 parallel incisions through cartilage to excise kinked portion
- cautery used to heat cartilage and bend back to normal position (newer technique)
Describe prolapsed gland of the nictitiating membrane (PGNM).
- "cherry eye"
- congenital weakness of the anchoring ligament--> prolapse and swelling of GNM over the margin of the third eyelid
- cockers, bulldogs, beagle, boston terrier, mastiff, burmese cats
How is cherry eye treated surgically?
- REPLACE THE GLAND!! don't remove it b/c it produces up to 50% of aqueous portion of tears (these breeds are also ironically predisposed to KCS)
- pocket imbrication technique- expose bulbar surface of NM, make elliptical incision around gland, undermine conjunctival epithelial and create pocket, cushings pattern to wrap pocket around gland
What is the post-op care and prognosis of a repaired cherry eye?
- triple antibiotic solution TID 7-10 days
- risk for KCS
- 25% recur
- nictitans may remain slightly elevated
What are potential causes for elevation of the NM? (6)
- [enophthalmus] loss of retrobulbar muscle and fat d/t dehydration/ cachexia/ old age, sympathetic denervation, active globe retraction (pain, tetanus)
- [exophthalmus] retrobulbar space-occupying mass
What is Haw's syndrome in cats?
- bilateral third eyelid elevation- cause unknown
- often associated with diarrhea
What tumor commonly affects the NM in cattle?
What tumor commonly affects the NM in old dogs and cats?
adenocarcinoma of the GNM (may look similar to cherry eye)
What are inflammatory diseases of the NM? (2)
- follicular conjunctivitis (lymphoid follicles visible on conjunctival surface, young dogs)
What is plasmoma?
immune-mediated lymphoplasmacytic inflammation of the NM
What are clinical signs of plasmoma? (5)
- reddening, thickening, depigmentation of the NM margin
- often associated with chronic pannus!
- Dx on clinical signs +/- cytology
How is plasmoma treated? (4)
- corticosteroids topically
- topical cyclosporine or tacrolimus
- limit UV light exposure
Conjunctivitis is ______________, but it is not _____________.
a sign of underlying disease; a primary diagnosis
What is follicular conjunctivitis? What areas does it affect? How is it treated?
- presence of lymphoid follicles
- bulbar surface of nictitans
- 0.1% dexamethasone topical
What is contraindicated in managing FHV-1 conjunctivitis?
What is the most common conjunctival tumor in cattle and horses?
What are causes of NM elevation? (4)
- enophthalmos (cachexia, dehydration, muscle, fat atrophy)
- Horner's syndrome
- exophthalmos (retrobulbar space occupying mass)
- Haw's syndrome (cats)