Definition

Inflammation of the conjunctiva, the vascularized mucous membrane that covers the anterior portion of the sclera (bulbar conjunctiva) and lines the eyelids (palpebral conjunctiva) and third eyelid.

Pathophysiology

May be primary or secondary to adnexal or ocular disease.

Systems Affected

Ophthalmic-ocular with possible eyelid involvement.

Genetics

N/A

Incidence/Prevalence

Common

Geographic Distribution

N/A

Signalment

Signs

• Blepharospasm
• Conjunctival hyperemia
• Ocular discharge-serous, mucoid, or mucopurulent
• Chemosis
• Conjunctival follicles
• Upper respiratory infection-possible with infectious etiologies

Causes

Risk Factors

Stress or immune system compromise (FHV)

Differential Diagnosis

• Must distinguish primary conjunctivitis from secondary conjunctival hyperemia (see Red Eye).
• Thorough systematic ophthalmic exam allows rule-out of other potential diseases (e.g., ulcers, uveitis, glaucoma, orbital disease); assess pupil size and symmetry, look for aqueous flare, perform IOP and fluorescein staining.
• Deeper, darker, more linear and immobile blood vessel injection indicates episcleral vasculature congested due to intraocular disease.
• Conjunctival mass biopsy will differentiate neoplasia (lymphoma and squamous cell carcinoma most common).

CBC/Biochemistry/Urinalysis

Normal, except with systemic disease

Other Laboratory Tests

Infectious-consider serologic tests for FeLV and FIV; rule out underlying immunocompromise.

Imaging

N/A

Diagnostic Procedures

• Thorough adnexal examination-rule out eyelid abnormalities and foreign bodies under eyelids or third eyelid.
• Complete ophthalmic examination-rule out other ocular diseases (e.g., uveitis and glaucoma).
• Fluorescein stain-assess for corneal ulceration or dendritic lesions (FHV) and observe nares for stain passage to indicate nasolacrimal system patency.
• Nasolacrimal flush-considered to rule out dacryocystitis or nasolacrimal system obstruction.
• Bacterial culture if initial treatment is unsuccessful; -specimen is taken before anything is placed in the eye (e.g., topical anesthetic, fluorescein, flush) to prevent inhibition or dilution of bacterial growth.
• Schirmer tear test-if ocular surface appears visibly dry; performed before anything is placed in the eye.
• Conjunctival cytology-may reveal a cause (rare); eosinophils diagnose eosinophilic conjunctivitis; may see degenerate neutrophils and intracytoplasmic bacteria, which indicate bacterial infection; may see intracytoplasmic inclusion bodies with chlamydial or mycoplasmal infection; rarely see intranuclear FHV inclusions.
• Conjunctival biopsy-“snip biopsy” may be useful with mass lesions and immune-mediated disease or chronic disease.
• PCR testing for Chlamydia or FHV.
• Virus isolation or IFA testing for FHV; false-positive result if fluorescein staining is done before IFA testing.
• Serologic test for FHV antibodies-not useful due to widespread exposure and vaccination.

Pathologic Findings

• Biopsy-typical signs of inflammation (e.g., neutrophils and lymphocytes); possibly infectious agents.
• Histopathology of mass lesions may reveal neoplasia (e.g., squamous cell carcinoma and lymphoma).

Appropriate Health Care

• Primary-often outpatient.
• Secondary to other diseases (e.g., ulcerative keratitis, uveitis, glaucoma)-may need hospitalization to address a severe underlying ophthalmic issue.

Nursing Care

Irritant induced conjunctivitis-flush ocular surfaces and remove foreign body if observed.

Activity

• No restriction for most patients.
• Suspected contact irritant or acute allergic disease-prevent contact with the offending agent.
• Suspected FHV-minimize stress.
• Do not expose patients with infectious disease to susceptible animals.

Diet

• No change for most patients.
• Suspected underlying skin disease and/or food allergy-food elimination diet recommended.

Client Education

• When solutions and ointments are prescribed, instruct the client to use the solution(s) before the ointment(s) and wait at least 5 minutes between treatments.
• If copious discharge is noted, instruct the client to clean the eyes before giving medication.
• Instruct the client to call for instructions if the condition fails to improve or worsens, which indicates that the condition may not be responsive, may be progressing, or that the animal may be having an adverse reaction to a prescribed medication.

Surgical Considerations

• Lipogranulomatous conjunctivitis-surgical incision and curettage of glandular material and inflammatory infiltrates.
• Entropion, distichia, or other eyelid disease-perform temporary or permanent surgery depending on the findings, signalment and history.
• Nasolacrimal duct obstruction-difficult; treatment often not recommended (see Epiphora).
• Conjunctival neoplasia-depending on tumor type and extent of involvement may involve local excision and adjunctive therapy (-irradiation, cryotherapy), enucleation, or exenteration.
• Symblepharon-conjunctival adhesions may require surgical resection once active infection is controlled.
• Corneal sequestration-keratectomy often recommended (see Corneal Sequestrum).

Drug(s) Of Choice

Contraindications

• Topical corticosteroids-avoid with known or suspected infectious conjunctivitis; may result in FHV recrudescence and predispose to corneal sequestrum formation; never use if corneal ulceration is noted.
• Valacyclovir should never be used in cats.

Precautions

• Topical medications may be irritating.
• Monitor all patients treated with topical corticosteroids for signs of corneal ulceration; discontinue agent immediately if corneal ulceration occurs.

Possible Interactions

N/A

Alternative Drug(s)

Other corticosteroids-1% prednisolone acetate; betamethasone.

Patient Monitoring

Recheck shortly after beginning treatment (at 5 days); then in 2 weeks or as needed.

Prevention/Avoidance

• Treat any underlying disease that may be exacerbating the conjunctivitis.
• Minimize stress for patients with herpetic disease.
• Isolate patients with infectious conjunctivitis to prevent spread.
• Prevent reexposure to infectious sources.
• Vaccination recommended; infection is still possible if the cat was exposed to an infectious agent before being vaccinated (e.g., FHV infection from an infected queen).

Possible Complications

• Corneal sequestration (black lesion representing necrotic cornea and possibly associated with FHV)-usually requires surgical keratectomy.
• Symblepharon (adhesions between the conjunctival surfaces ± cornea)-may require surgical intervention.
• KCS-most likely from chronic FHV.

Expected Course and Prognosis

• FHV-most patients become chronic carriers; episodes less common as patient matures; may see repeated exacerbations; tend to note more severe clinical signs at times of stress or immunocompromise.
• Bacterial conjunctivitis-usually resolves with appropriate administration of antibiotic.
• Immune-mediated diseases (e.g., eosinophilic)-control not cure; may require chronic treatment at the lowest level possible.
• If an underlying disease is found (e.g., KCS, entropion), resolution may depend on appropriate treatment and resolution of the disease.

Associated Conditions

FeLV and FIV-may predispose patient to the chronic carrier state of FHV conjunctivitis.

Age-Related Factors

FHV-tends to be more severe in kittens and in old cats with waning immunity.

Zoonotic Potential

Chlamydophila felis-low

Pregnancy/Fertility/Breeding

• Use topical and systemic medications with caution, if at all, in pregnant animals.

See Also

• Keratoconjunctivitis Sicca
• Red Eye
• Ophthalmia Neonatorum
• Corneal Sequestrum

Abbreviations

• FeLV = feline leukemia virus
• FHV = feline herpesvirus
• FIV = feline immunodeficiency virus
• IFA = immunofluorescent antibody test
• KCS = keratoconjunctivitis sicca
• PCR = polymerase chain reaction

Client Education Handout Available Online