How should I treat bacterial, viral, and allergic conjunctivitis?

Treatment of Conjunctivitis

For bacterial conjunctivitis, prescribe a 5-7 day course of broad-spectrum topical antibiotic (moxifloxacin 0.5% or polymyxin B/trimethoprim) three to four times daily; for viral conjunctivitis, provide only supportive care with artificial tears and cold compresses; and for allergic conjunctivitis, use topical antihistamines with mast cell-stabilizing activity such as olopatadine or ketotifen as first-line treatment. 1

Diagnostic Approach: Distinguishing the Three Types

Before treating, you must differentiate between bacterial, viral, and allergic etiologies based on specific clinical features:

Bacterial Conjunctivitis

• Discharge character: Mucopurulent or purulent discharge with eyelids matted shut on waking is the hallmark 1, 2
• Conjunctival reaction: Papillary rather than follicular reaction on tarsal conjunctiva 1
• Laterality: Can be unilateral or bilateral 1
• Associated features: May have concurrent otitis media, sinusitis, or pharyngitis, especially in children 1
• Preauricular lymphadenopathy: Less common unless caused by hypervirulent organisms 1

Viral Conjunctivitis

• Discharge character: Watery discharge, not purulent 1, 2
• Conjunctival reaction: Follicular reaction on inferior tarsal conjunctiva 1, 2
• Onset and laterality: Abrupt onset, often starts unilateral but becomes sequentially bilateral within days 1, 2
• Associated features: Concurrent upper respiratory infection, preauricular lymphadenopathy (especially adenovirus), subconjunctival hemorrhages, chemosis, eyelid swelling 1
• Duration: Self-limited, typically resolves within 5-14 days 1

Allergic Conjunctivitis

• Distinguishing symptom: Itching is the most consistent and distinguishing feature 1, 2
• Discharge: Watery with mild mucous component 1
• Laterality: Always bilateral 1
• Associated features: History of atopy, asthma, or eczema; concurrent allergic rhinitis; eyelid edema; periorbital hyperpigmentation 1, 2
• Preauricular lymphadenopathy: Absent 1

Treatment Algorithm by Etiology

Bacterial Conjunctivitis Treatment

Mild to Moderate Cases:

• Prescribe a 5-7 day course of broad-spectrum topical antibiotic 1, 3
• No single antibiotic is superior, so choose based on convenience and cost 1, 3
• First-line options: Moxifloxacin 0.5% three times daily, polymyxin B/trimethoprim four times daily, or erythromycin ointment 1, 3
• Fourth-generation fluoroquinolones (moxifloxacin) provide superior gram-positive coverage including some MRSA strains 3
• Topical antibiotics provide earlier clinical remission (68.2% cure vs 55.5% placebo by days 4-9) and allow faster return to work or school 1, 3

Important caveat: Mild bacterial conjunctivitis is self-limited in immunocompetent adults, with 64% resolving spontaneously by days 6-10 without treatment 1, 3

Severe Cases or Treatment Failure:

• Obtain conjunctival cultures and Gram staining before initiating treatment 1, 3
• Consider MRSA if patient is from nursing home or has community-acquired infection 3
• MRSA isolates are generally resistant to fluoroquinolones but susceptible to vancomycin; may require compounded topical vancomycin 3
• If no improvement after 48-72 hours, obtain cultures and consider resistant organisms 3

Special High-Risk Bacterial Forms Requiring Systemic Treatment:

Gonococcal Conjunctivitis:

• Clinical presentation: Marked eyelid edema, severe hyperpurulent discharge, rapid progression, risk of corneal perforation 1, 2
• Treatment: Ceftriaxone 250 mg IM single dose PLUS azithromycin 1 g oral single dose 3
• Additional measures: Topical antibiotics, saline lavage, daily monitoring until resolution 1, 3
• Critical: Obtain cultures and Gram stain before treatment; evaluate and treat sexual partners 1, 3

Chlamydial Conjunctivitis:

• Treatment: Azithromycin 1 g oral single dose OR doxycycline 100 mg oral twice daily for 7 days 3
• Rationale: Topical therapy alone is inadequate; more than 50% of infants have concurrent infection at other sites 1, 3
• Critical: Evaluate and treat sexual partners; re-evaluate after treatment completion 1, 3

Neonatal Conjunctivitis:

• Gonococcal: Ceftriaxone 25-50 mg/kg IV or IM single dose (max 125 mg) 3
• Chlamydial: Erythromycin base or ethylsuccinate 50 mg/kg/day oral divided into 4 doses for 14 days 3
• Critical: Requires hospitalization, daily ophthalmology follow-up, and evaluation for sexual abuse in older children 1, 3

Viral Conjunctivitis Treatment

Standard Management (Adenovirus):

• Do NOT prescribe antibiotics – they provide no benefit and may cause toxicity 1, 3
• Supportive care only: Refrigerated preservative-free artificial tears four times daily, cold compresses, topical antihistamines for symptomatic relief 1, 3
• Patient education: Highly contagious; minimize contact with others for 10-14 days from symptom onset 1
• Infection control: Strict hand hygiene with soap and water, avoid sharing towels/pillows, disinfect surfaces 1

Severe Adenoviral Cases (with marked chemosis, severe lid swelling, epithelial sloughing, or membranous conjunctivitis):

• Consider topical corticosteroids (fluorometholone, rimexolone, or loteprednol) with extreme caution 1, 3
• Mandatory monitoring: Regular IOP measurement and pupillary dilation to evaluate for cataract 1, 3
• Re-evaluate within 1 week for severe cases 1
• Caution: Corticosteroids may prolong viral shedding and worsen HSV infections 1, 3

Herpes Simplex Virus (HSV) Conjunctivitis:

• Topical antivirals: Ganciclovir 0.15% gel three to five times daily OR trifluridine 1% solution five to eight times daily 3
• Add oral antivirals: Acyclovir, valacyclovir, or famciclovir 3
• NEVER use topical corticosteroids without antiviral coverage – they potentiate HSV infection and can cause corneal perforation 1, 3
• Distinguishing features: Usually unilateral, vesicular rash or ulceration of eyelids, dendritic epithelial keratitis 1

Allergic Conjunctivitis Treatment

First-Line Treatment:

• Topical antihistamines with mast cell-stabilizing activity: Olopatadine or ketotifen 1, 3
• Environmental modifications: Wear sunglasses as allergen barrier, use cold compresses, refrigerated artificial tears, avoid eye rubbing 1

Adjunctive Measures:

• Allergen avoidance strategies 1
• Oral antihistamines (less effective than topical for ocular symptoms) 1

Refractory Cases:

• Short-term topical corticosteroids: Brief 1-2 week course with low side-effect profile (fluorometholone, rimexolone, or loteprednol) 1, 3
• Monitor: IOP and cataract formation with periodic pupillary dilation 1
• Alternative: Cyclosporine drops 0.05% to 1% 3

Severe Cases:

• Allergen-specific immunotherapy, more beneficial in children than adults 1
• Multidisciplinary approach with allergists 1

Critical Red Flags Requiring Immediate Ophthalmology Referral

Refer urgently if ANY of the following are present: 1, 3

• Visual loss or decreased vision
• Moderate or severe pain (beyond mild irritation)
• Severe purulent discharge (possible gonococcal infection)
• Corneal involvement (opacity, infiltrate, ulcer, or fluorescein uptake)
• Conjunctival scarring
• Lack of response to therapy after 3-4 days
• Recurrent episodes
• History of HSV eye disease
• Immunocompromised state
• Recent ocular surgery
• Vesicular rash on eyelids or nose
• Neonatal conjunctivitis (any age <28 days)

Common Pitfalls to Avoid

• Never use antibiotics indiscriminately for viral conjunctivitis – contributes to resistance and causes unnecessary toxicity 1, 3
• Never use combination antibiotic-steroid drops (e.g., Tobradex) without definitively excluding viral etiology – steroids can exacerbate viral infections and prolong viral shedding 3
• Never use topical corticosteroids in HSV conjunctivitis without antiviral coverage – potentiates infection 1, 3
• Never prescribe oral antibiotics (e.g., Augmentin) for routine bacterial conjunctivitis – topical antibiotics achieve high tissue concentrations directly at infection site; oral antibiotics cannot reach therapeutic levels in conjunctiva 3
• Avoid chronic use of topical vasoconstrictors – causes rebound vasodilation 3
• Do not miss gonococcal or chlamydial conjunctivitis – requires systemic treatment and can cause corneal perforation or systemic spread 1, 3
• Consider sexual abuse in preadolescent children with gonococcal or chlamydial conjunctivitis 3
• Avoid contact lens wear during any form of infectious conjunctivitis 1

Follow-Up Recommendations

• Bacterial conjunctivitis: Return if no improvement in 3-4 days 3
• Viral conjunctivitis (severe cases): Re-evaluate within 1 week 1
• Gonococcal conjunctivitis: Daily visits until resolution 1, 3
• Chlamydial conjunctivitis: Re-evaluate after treatment completion 1, 3
• Patients on topical corticosteroids: Regular IOP monitoring and periodic pupillary dilation 1, 3