Conjunctiva– Metzler Flashcards

1
Q

What structures of the eye does the conjunctiva cover?

A

covers everything but the cornea

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2
Q

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

A

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

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3
Q

What are the clinical features of conjunctivitis?

A

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

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4
Q

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

A
  • 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)
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5
Q

What are the most common causes of canine conjunctivitis?

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

A
  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
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6
Q

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

A
  • 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
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7
Q

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

A

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

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8
Q

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?

A

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

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9
Q

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

a) clinical signs
b) diagnostic tests

A
  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
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10
Q

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

A

Squamous cell carcinoma

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11
Q

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

A

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

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12
Q

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

A
  • structural support; helps nictitans maintain concave curvature that conforms to the globe
  • cartilage deformity/”scrolled cartilage”
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13
Q

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?

A
  • 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
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14
Q

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

A

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

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15
Q

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

A
  • 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
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16
Q

What are the causes of NM elevation?

A
  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
17
Q

Name 3 common tumors of the NM

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