Conjunctiva

Question 1

Clinical features of conjunctivitis:

Answer 1

Diffuse hyperemia, chemosis, ocular discharge (serous, mucoid or mucopurulent) and blepharospasm.

Question 2

Hyperemia

Answer 2

diffuse redness of conjunctiva is due to engorged capillaries. There may be injection of the larger conjunctival blood vessels as well. The conjunctival vessels are mobile and tortuous.

Question 3

episcleral injection

Answer 3

by engorged straight vessels over the sclera that do not move and usually indicate intraocular disease.

Question 4

Trick to tell apart deep vessels and superficial vessels

Answer 4

Hyperemic vessels can be ‘blanched out’ with a drop of epinephrine. Deep vessels will not ‘blanch out’.

Question 5

chemosis

Answer 5

edema and appears as a ‘swelling’ or thickening of the conjunctiva.

Question 6

Exudate

Answer 6

Conjunctival discharge may be mucoid, mucopurulent, purulent, eosinophilic, septic etc. Cytology should be performed on any ocular discharge.

Question 7

Causes of conjunctivitis in the dog

Answer 7

In the dog, conjunctivitis is most commonly caused by KCS, environmental irritants and allergies. Recently, canine herpes virus 1 has been associated with conjunctivitis in dogs.

Question 8

Causes of conjunctivitis in the cat

Answer 8

In the cat, conjunctivitis is usually due to an infectious agent: Feline Herpes Virus (FHV1), Chlamydia felis and possibly Bartonella, are the most common causes.
These are important considerations when determining treatment for conjunctivitis.

Question 9

Using corticosteroids in feline conjunctivitis

Answer 9

Steroids are contraindicated for infectious etiologies, so they are rarely indicated in feline conjunctivitis. Use of steroids (topical or systemic) may cause recrudescence of FHV1 ocular disease. Feline conjunctivitis will be covered in a separate chapter with feline ocular diseases.

Question 10

Causes of conjunctivitis in the horse

Answer 10

In the horse, ulcers and intraocular disorders are common causes of conjunctivitis and must be ruled out prior to initiating treatment. Conjunctivitis is associated with many systemic diseases (see equine chapter).

Question 11

Differentials for conjunctivitis in the dog

Answer 11

KCS, irritants, allergies, follicular conjunctivitis, lymphoid hyperplasia

Question 12

Corticosteroids to use after you’ve ruled out corneal ulcers

Answer 12

Use the least potent drug that is effective for problem:
Hydrocortisone- mild allergies and irritants – does not penetrate cornea
Dexamethasone – follicular conjunctivitis, strong steroid, penetrates cornea
Prednisolone acetate penetrates cornea (prednisolone phosphate does not). It is not usually indicated for treatment of conjunctivitis but is used for anterior uveitis.

Question 13

allergies as a cause of conjunctivitis

Answer 13

They may be due to atopy, food, contact, medications etc. It

Question 14

treatment of allergies

Answer 14

These patients may respond to topical antibiotics +/- steroids, and topical mast cell blockers (ketotifen).

Question 15

Presentation of dogs who present for follicular conjunctivitis

Answer 15

This diagnosis is specific for a clinical presentation seen in young dogs. Conjunctival hyperemia with variable degrees of discomfort and ocular discharge are present bilaterally. The only abnormality found is lymphoid hyperplasia on the bulbar aspect of the third eyelid.

Question 16

Treatment of follicular conjunctivitis

Answer 16

The clinical signs resolve with use of topical dexamethasone (NPDex) every 8 hours then tapered to the lowest dosing frequency that controls the clinical signs. The dogs generally ‘outgrow’ this condition at 18-24months of age.

Question 17

Corneal Ulcers:

Answer 17

(loss of corneal epithelium exposing corneal stroma)

Question 18

Nasal-lacrimal obstruction/dacryocystitis - clinical signs

Answer 18

These patients have copious tearing and purulent discharge. They are not usually painful until flushing or manipulation of the duct is attempted. Fluorescein does not exit the nares but may have purulent discharge from the puncta when flushed.

Question 19

Cause of N-S obstruction and dacrocystitis

Answer 19

Causes of nasal-lacrimal obstruction are foreign body, dental abscess, neoplasia of sinus or trauma.

Question 20

oral/otic disease affecting the eye is common in what species

Answer 20

This is a common problem in rabbits.

Question 21

KCS in dogs should be ruled out with what other disease and why?

Answer 21

KCS should be ruled out in dogs with chronic otitis due to inflammation associated with the parasympathetic nerve as it runs with the facial nerve through the petrous temporal bone.

Question 22

Retrobulbar disease

Answer 22

Infection, inflammation or tumor in the tissue surrounding the eye will cause varying degrees of conjunctival hyperemia, injection and discharge.

Question 23

Equine dfdx for conjunctivitis

Answer 23

Parasites, SCC, solar (actinic), blunt or sharp trauma, eyelid abnormalities need to be ruled out as causes of conjunctivitis. Topical BNP is a good first choice when no underlying cause is seen. Any case that does not resolve in a day or two should be reassessed.