Canis ISSN: 2398-2942

Conjunctivitis

Introduction

• Inflammation of the mucous membrane lining the eyelids, membrana nictitans, scleral part of the globe and lacrimal canaliculi.
• Common - acute, chronic, allergic and 'special' types.
• Cause: varied - traumatic, infectious, immune-mediated; may be secondary to other concurrent ocular or systemic disease.
• Signs: congestion of conjunctival blood vessels, swelling, ocular discharge (lacrimous/serous → mucopurulent), blepharospasm, photophobia; less commonly follicle formation, edema.
• Diagnosis: physical examination; swabs, scrapings → microbiology; Schirmer tear test.
• Treatment: depends on cause, eg topical antibiotics, removal of any physical cause, corticosteroids, analgesia.
• Prognosis: good.
  Print off the owner factsheet on Conjunctivitis in dogs to give to your client.

Pathogenesis

Etiology

• Entropion Entropion.
• Foreign body.

• Staphylococcus Staphylococcus spp.
• Beta hemolytic streptococci Streptococcus spp.
• Proteus.
• E. coli Escherichia coli.
• Pseudomonas Pseudomonas aeruginosa.
• Neisseria.
• Mycoplasma Mycoplasmas and ureaplasmas - often isolated, probably not primary pathogen.
• Distemper virus Canine distemper disease.
• May be primary or secondary, ie extension from systemic infection (rare).

• Atopy Skin: atopy.
• Contact allergens Skin: allergic contact dermatitis.
• Bacterial, eg Staphylococcal allergens.

• Follicular - unknown.
• Plasma cell/lymphocytic - associated with corneal pannus Chronic superficial keratitis.
• Neoplasia - melanomas, hemangiomas, lymphoma.

Predisposing factors

• Breed.
• Long facial hair.
• Very active outdoors.

Specific

• Deficient tear production.

Pathophysiology

• Trauma → tissue injury +/- introduction of bacteria → inflammatory response.

• Systemic infection → localization of micro-organism in mucous membranes including conjunctiva → inflammatory response.

• Misdiagnosis/ineffective therapy.

• Allergen → anaphylactic/immune-complex/cell-mediated response → chemosis, profuse lacrimation.

• Follicular - lymphoid hyperplasia on membrane and palpebral conjunctivae → trauma → inflammatory response.
• Plasma cell/lymphocytic - with corneal pannus Chronic superficial keratitis.
• Keratoconjunctivitis sicca Keratoconjunctivitis sicca.

• Trauma to conjunctiva → inflammation and possible epthelial ulceration.
• Chronic disease → squamous metaplasia of epithelium.
• Primary inflammation of conjunctiva may → predisposition to secondary bacterial infection.
• Can be primary, eg allergic, infectious, environmental and KCS or secondary to an underlying ocular or systemic disease, eg glaucoma, uveitis, neoplasia, keratitis.
• The loose arrangement of the conjunctival stroma permits rapid edema.
• Stroma vasculature and lymphoid tissue permit acute development of hyperemia.
• Multinucleated giant cells are seen in chronic conjunctivitis.
• Keratinized epithelial conjunctival cells and goblet cell proliferation occur in chronic conjunctivitis.

Timecourse

• Acute conjunctivitis may be the first manifestation of anteroir uveitis, corneal ulceration and glaucoma.

Diagnosis

Treatment

Prevention

Outcomes