Conjunctiva– Metzler

Question 1

What structures of the eye does the conjunctiva cover?

Answer 1

covers everything but the cornea

Question 2

What is the normal flora of the conjunctiva and why is it important?

Answer 2

Mostly gram + : Staph. and Strep. spp.
Few gram – : E. coli, Pseudomonas spp. (less pathogenic strains), Actinobacter
Fungal organisms (mainly in large animals)
-Important because you want to choose antibiotics that act against gram + and – bacteria because the normal flora in the eye can become opportunistic pathogens

Question 3

What are the clinical features of conjunctivitis?

Answer 3

conjunctival swelling (chemosis), hyperemia, conjunctival thickening, conjunctival follicles, ocular discharge

Question 4

How can you differentiate conjunctival and episcleral hyperemia both visibly and with pharmacologic testing? Why is it important to know the difference?

Answer 4

• Conjunctival hyperemia– vessels are mobile and tortuous
• Episcleral vessel engorgement– vessels are stationary ands straight
• conjunctival hyperemia vessels will blanch immediately with the administration of topical epinephrine/phenylephrine, but episcleral vessels will take multiple minutes
• Conjunctival hyperemia indicate surface disease (ex. dry eye, corneal disease, eyelid abnormalities)
• Episcleral vessels indicate intraocular disease (ex. glaucoma, uveitis)

Question 5

What are the most common causes of canine conjunctivitis?

a) how are they diagnosed?
b) how are they treated?

Answer 5

1. Keratoconjunctivitis sicca (dry eye)
   a) Schirmer tear test (<15mm/min)
   b) artificial tears
2. Follicular conjunctivitis
   a) lymphoid follicles visible with magnification or cytology
   b) 0.1% dexamethasone
3. Allergic conjunctivitis
   a) cytology–presence of PMNs and bacteria, culture and sensitivity
   b) broad-spectrum antibiotics until sensitivity results are in

Question 6

What is follicular conjunctivitis? What area of the conjunctiva does it affect and how is it treated?

Answer 6

• presence of lymphoid follicles resulting form immune-mediated response or chronic irritation
• bulbar surface of nictitans&raquo_space; palpebral surface of nictitans
• treated using topical steroids: 0.1% dexamethasone

Question 7

Is a culture/susceptibility an important diagnostic procedure to work up canine conjunctivitis? Why or why not?

Answer 7

Not important because it will always be positive for bacterial flora and because 1º bacterial infections are rare in dogs

Question 8

What is the most common cause of feline conjunctivitis?

a) how is it diagnosed?
b) how is it treated?
c) what treatment is contraindicated in this disease?

Answer 8

Feline Herpesvirus–1
a) fluorescent staining of cornea for punctate/tiny dendritic ulcers (pathognomonic)
b)
- topical antibiotics (oxytetracycline, erythromycin) to address 2º bacterial infections
-topical antivirals if corneal ulceration is present: Cidofovir, Famcyclovir (Famvir)
-probiotic to lessen clinical signs
c) steroids because they promote recrudescence of latent virus, prolong virus shedding, exacerbate clinical signs and allow viral penetration into stroma

Question 9

What are the two most common causes of bovine conjunctivitis and how would you distinguish between them?

a) clinical signs
b) diagnostic tests

Answer 9

1. Infectious Bovine Rhinotracheitis (IBR; herpesvirus)
   a) hyperemia, chemoses, serous discharge that becomes mucopurulent, pseudomembrane, PERIPHERAL corneal edema; unilateral or bilateral
   b) herpes IFA
2. Infectious Bovine Keratoconjunctivitis (IBK; moraxella bovis, “pinkeye”)
   a) epiphora, blepharospasm, photophobia, conjunctival hyperemia, chemosis, CENTRAL corneal abcess that later becomes an ulcer
   b) culture

Question 10

What is the most common conjunctival tumor in horses and cattle?

Answer 10

Squamous cell carcinoma

Question 11

How is squamous cell carcinoma of the third eyelid in a horse best treated?

Answer 11

–surgical excision with adjunctive therapy associated with least chance of recurrence

Question 12

What is the purpose of the “T” cartilage of the nictitans and what congenital abnormality occurs with this cartilage in large breed dogs?

Answer 12

• structural support; helps nictitans maintain concave curvature that conforms to the globe
• cartilage deformity/”scrolled cartilage”

Question 13

Why is it important to replace, rather than remove, a prolapsed gland of the third eyelid (aka “cherry eye)? What surgical procedure is recommended for replacement?

Answer 13

• The lacrimal glands of the third eyelid produces up to 50% of the aqueous component of the tear film. If you remove the third eyelid, you risk the patient getting KCS
• pocket imbrication technique

Question 14

What is the only indication for surgical removal of the nictitans/gland of the nictitans?

Answer 14

neoplasia of the nictitans (ex. adenocarcinoma of the gland of nictitans, seen in older dogs and cats)

Question 15

What is “plasmoma” and how would you treat it? What breeds are commonly affected?

Answer 15

• Plasmoma is an irregular thickening, reddening, and depigmentation of the margin of the nictitans
• usually bilateral
• german shepherds, collies, sight-hounds, and related breeds
• treated via topical corticosteroids (gradually wean), topical cyclosporine/tacrolimus/optimmune (indefinitely), beta-radiation, chemotherapy

Question 16

What are the causes of NM elevation?

Answer 16

1. enophthalmos– loss of retrobulbar muscle/fat, sympathetic denervation (Horner’s syndrome), or active globe retraction resulting from tetany (tetanus, strychnine) or painful ocular disease (corneal ulcer, glaucoma, uveitis)
2. exophthalmos– retrobulbar space-occupying mass
3. Haw’s syndrome in cats–bilateral protrusion resulting from loss of sympathetic tone but without other signs of Horner’s syndrome

Question 17

Name 3 common tumors of the NM

Answer 17

1. SCC
2. Lymphosarcoma
3. Adenocarcinoma of the GNM