C: Conjunctivitis

Conjunctivitis—Cats

BASICS

DEFINITION

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

PATHOPHYSIOLOGY

May be primary (e.g., infectious) or secondary to an underlying ocular or systemic disease (e.g., glaucoma, uveitis, immune-mediated disease, neoplasia).

SYSTEMS AFFECTED

Ophthalmic—ocular with occasional lid involvement (e.g., blepharoconjunctivitis).

GENETICS

N/A

INCIDENCE/PREVALENCE

Common

GEOGRAPHIC DISTRIBUTION

N/A

SIGNALMENT

Species

Cats

Breed Predilections

Infectious—purebred cats seem predisposed

Mean Age and Range

Infectious—most commonly affects young animals

Predominant Sex

N/A

SIGNS

Blepharospasm
Conjunctival hyperemia
Ocular discharge—serous, mucoid, or mucopurulent
Chemosis
Bulbar or palpebral conjunctiva—may be primarily involved
Upper respiratory infection—possible

CAUSES

Viral

FHV—most common infectious cause; only one that leads to corneal changes (e.g., dendritic or geographic ulcers).
Calicivirus.

Bacterial

Primary condition (i.e., not secondary to another condition such as KCS)—rare, except for chlamydia and mycoplasma.
Neonatal—accumulation of exudates, often with a bacterial or viral component; seen before lid separation.

Immune Mediated

Eosinophilic.
Related to systemic immune-mediated diseases—pemphigus.

Neoplastic, Pseudoneoplastic

Rare; lymphosarcoma and squamous cell carcinoma most common.

Secondary to Adnexal Disease

Aqueous tear film deficiency.
May develop KCS as a result of scarring (see Keratoconjunctivitis Sicca).
Lid diseases (e.g., entropion)—may lead to clinical signs of conjunctivitis.
Secondary to obstruction of the outflow portion of the nasolacrimal system—obstructed nasolacrimal duct.

Secondary to Trauma or Environmental Causes

Conjunctival foreign body.
Irritation from dust, chemicals, or ophthalmic medications.

Secondary to Other Ocular Diseases

Ulcerative keratitis.
Anterior uveitis.
Glaucoma.

RISK FACTORS

N/A

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Primary—must distinguish from condition that is secondary to other ocular diseases.
Intraocular disease—involvement of the bulbar conjunctiva with minimal or no involvement of the palpebral conjunctiva.
Primary or allergic—involvement of mainly the palpebral conjunctiva, sparing the bulbar conjunctiva; consider primary and secondary causes if both surfaces are involved.
Must differentiate between conjunctival vessels (freely mobile and will blanch with sympathomimetics) and episcleral (deep) vessels (immobile and do not blanch with sympathomimetics)—episcleral congestion indicates intraocular disease; conjunctival hyperemia may be a sign of primary conjunctivitis or intraocular disease.

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

Complete ophthalmic examination—rule out underlying intraocular diseases (e.g., uveitis and glaucoma).
Thorough adnexal examination—rule out lid abnormalities and foreign bodies in cul-de-sacs or under nictitans.
Nasolacrimal flush—considered to rule out nasolacrimal disease.
Aerobic bacterial culture and sensitivity—with mucopurulent discharge; specimens ideally taken before anything is placed in the eye (e.g., topical anesthetic, fluorescein, and flush) to prevent inhibition or dilution of bacterial growth.
Conjunctival cytology—may reveal a cause (rare); eosinophils and basophils may help diagnose allergic and eosinophilic conjunctivitis but are rarely seen with allergic conjunctivitis except on biopsy; may see degenerate neutrophils and intracytoplasmic bacteria, which indicate bacterial infection; may see inclusion bodies with chlamydial or mycoplasmal infection; rarely see FHV inclusions.
Conjunctival scrapings for FHV—use PCR or an IFA technique; but may note false-positive results with chronic disease; PCR more sensitive and test of choice; may note false-positive result if fluorescein staining is done before IFA testing.
Conjunctival scrapings for chlamydia—use special stains, which are fairly reliable.
Viral culture—not widely available but may help diagnose FHV.
Conjunctival biopsy—may be useful with mass lesions and immune-mediated disease; may help with chronic disease for which a definitive diagnosis has not been made.

PATHOLOGIC FINDINGS

Biopsy—typical signs of inflammation (e.g., neutrophils and lymphocytes); possibly infectious agents.
Histopathologic features of mass lesions (e.g., squamous cell carcinoma and lymphosarcoma)—consistent with similar lesions elsewhere.

TREATMENT

APPROPRIATE HEALTH CARE

Primary—often outpatient.
Secondary to other diseases (e.g., uveitis and ulcerative keratitis)—may need hospitalization while the underlying problem is diagnosed and treated.

ACTIVITY

Primary—no restriction for most patients.
Suspected contact irritant or acute allergic disease—prevent (if possible) contact with the offending agent.
Suspected FHV—minimizing stress recommended.
Do not expose patients to susceptible animals.

DIET

Suspected underlying skin disease and/or food allergy—food elimination diet recommended.

CLIENT EDUCATION

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

SURGICAL CONSIDERATIONS

Nasolacrimal duct obstruction—difficult; treatment often not recommended (see Epiphora).
Conjunctival neoplasia—may require only local resection; may involve excision followed by β-irradiation, cryotherapy, radiofrequency hyperthermia, enucleation, or exenteration, depending on the type of tumor and the extent of involvement.
Symblepharon—may require surgical resection once active conjunctival infection is controlled.
Corneal sequestration—keratectomy may be required.

MEDICATIONS

DRUG(S) OF CHOICE

Herpetic

Condition usually mild and self-limiting.
Antiviral treatment—indicated for herpetic keratitis, before keratectomy for corneal sequestrums suspected to be related to FHV, and for severe intractable conjunctivitis; drug penetration into the conjunctiva (vs. the cornea) poor; optional; treatment may be directed at controlling secondary bacterial infection only.
0.1% idoxuridine solution (available from compounding pharmacies)—topical q6h initially.
Vidarabine 3% ointment—topical q6h initially.
Trifluridine—recommended hourly for the first day, then 5 times a day.
Lysine 250–500 mg PO q12h for adult cat (efficacy is controversial).
Oral famciclovir was recently found to be effective and safe for use in cats, even though not approved for use in this species. Dosage is controversial—most commonly used as famciclovir 125 mg—1/4 tab PO q12h for 10 days; however, often used without complication at higher doses and for extended times.

Chlamydial or Mycoplasmal

Tetracycline ophthalmic ointment (Terramycin)—topically q6h; continue for several days past resolution of all clinical signs; recurrence or reinfection common; systemic treatment recommended by some authors for difficult cases.
Topical chloramphenicol or ciprofloxacin ophthalmic solutions q6–8h are alternatives to topical oxytetracycline ophthalmic ointment.
Azithromycin 5 mg/kg PO every 72 hours for 3 weeks.

Bacterial

Based on bacterial culture and sensitivity results.

Neonatal

Carefully open the lid margins (medial to temporal), establish drainage, and treat with topical antibiotic and an antiviral for suspected FHV.
Symblepharon (adhesions between the conjunctival surfaces and possibly the cornea)—common sequela; may require surgical intervention.

Eosinophilic

Topical corticosteroids—usual treatment; 0.1% dexamethasone generally effective when used 3 or 4 times daily; taper to the lowest effective dose.
Oral megestrol acetate—may help resistant condition; consider possible systemic side effects.
Cyclosporine—one recent report showed topical 1.5% solution to be safe and effective.

CONTRAINDICATIONS

Topical corticosteroids—avoid with known or suspected herpetic conjunctivitis; evidence shows that agents predispose the patient to corneal sequestrum formation; avoid if corneal ulceration is noted.

PRECAUTIONS

Topical aminoglycosides and antiviral medication 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; hydrocortisone.

FOLLOW-UP

PATIENT MONITORING

Recheck shortly after beginning treatment (at 5–7 days); then recheck as needed.

PREVENTION/AVOIDANCE

Treat any underlying disease that may be exacerbating the ocular disease—allergic or immune-mediated skin disease; KCS.
Prevent reexposure to source of infection.
Minimize stress for patients with herpetic conjunctivitis.
Isolate patients with infectious conjunctivitis to prevent spread.
Vaccination against viral causes—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
Symblepharon
KCS

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 antibiotics; if an underlying disease is found (e.g., KCS), resolution may depend on appropriate treatment and resolution of the disease.
Immune-mediated diseases (e.g., eosinophilic)—control not cure; may require chronic treatment at the lowest level possible.

MISCELLANEOUS

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

Chlamydia psittaci—low

PREGNANCY/FERTILITY/BREEDING

Use systemic antibiotics and corticosteroids with caution, if at all, in pregnant animals.
Absorption of topically applied medications should be considered a possibility, and the benefits of treatment should be weighed against the possible complications