How should I evaluate and manage a patient with red eye and a clear cornea?

Evaluation and Management of Red Eye with Clear Cornea

For a patient presenting with red eye and a clear cornea, the most likely diagnosis is conjunctivitis, and your primary task is to differentiate between viral, bacterial, and allergic etiologies based on discharge character, conjunctival reaction pattern, and associated symptoms—with viral cases requiring only supportive care while bacterial cases may benefit from topical antibiotics in moderate-to-severe presentations. 1

Initial Diagnostic Approach

Critical History Elements to Obtain

• Discharge character: Watery discharge suggests viral etiology, mucopurulent/purulent indicates bacterial, and minimal mucoid discharge with severe itching points to allergic conjunctivitis 1, 2
• Onset pattern: Abrupt onset with sequential bilateral involvement favors viral; unilateral or bilateral with matted eyelids suggests bacterial 1
• Associated symptoms: Itching as the predominant symptom is pathognomonic for allergic conjunctivitis; concurrent upper respiratory infection suggests viral etiology 1
• Contact lens history: Wearing schedule, overnight wear, tap-water exposure, and hygiene practices 3
• Sexual activity: In sexually active adults, consider gonococcal or chlamydial infection 1
• Systemic conditions: History of atopy, asthma, eczema (allergic); immunocompromise; autoimmune disease 1, 4

Physical Examination Findings That Differentiate Etiologies

• Follicular reaction on inferior tarsal conjunctiva with preauricular lymphadenopathy indicates viral conjunctivitis 1
• Papillary reaction with purulent discharge suggests bacterial conjunctivitis 1
• Chemosis and eyelid swelling can occur in severe viral cases, sometimes mimicking orbital cellulitis 1
• Subconjunctival hemorrhage is distinctive for viral conjunctivitis 1
• Absence of corneal involvement is key—if the cornea is clear, you are likely dealing with conjunctivitis rather than keratitis 3

Red Flags Requiring Immediate Ophthalmology Referral

Stop and refer urgently (within 24 hours) if any of the following are present: 1, 5

• Visual loss or decreased vision
• Moderate to severe ocular pain (not relieved by topical anesthetics)
• Photophobia
• Corneal involvement (opacity, haze, ulceration, or infiltrate)
• Severe purulent discharge suggesting gonococcal infection
• History of herpes simplex virus eye disease
• Immunocompromised state
• Conjunctival scarring
• Lack of response to appropriate therapy after 5-7 days
• Recurrent episodes

Management Algorithm by Etiology

Viral Conjunctivitis (Most Common)

Treatment is entirely supportive—antibiotics provide no benefit and should be avoided. 1

• Supportive care: Preservative-free artificial tears for symptomatic relief, cold compresses 1
• Topical antihistamines (olopatadine) may be used for symptomatic relief 1
• Patient education: Highly contagious for 10-14 days from symptom onset; strict hand hygiene with soap and water; avoid sharing towels/pillows; disinfect surfaces with EPA-registered disinfectant 1
• Natural course: Self-limited, typically resolves within 5-14 days 1
• Topical corticosteroids: Consider only for severe cases with marked chemosis, lid swelling, or subepithelial infiltrates causing visual symptoms—but this requires close ophthalmology follow-up for IOP monitoring and periodic pupillary dilation 1, 6

Common pitfall: Indiscriminate antibiotic use contributes to resistance and causes unnecessary toxicity without providing benefit 1

Bacterial Conjunctivitis

Mild cases are self-limited, but moderate-to-severe cases benefit from a 5-7 day course of broad-spectrum topical antibiotics. 1

• First-line options (no specific agent is superior—choose most convenient or least expensive): Erythromycin ointment, polymyxin B/trimethoprim drops, or fluoroquinolones 1
• No routine cultures needed for uncomplicated cases in otherwise healthy patients 1
• Obtain cultures in these high-risk situations: Neonatal conjunctivitis, suspected gonococcal infection, recurrent/severe/chronic purulent conjunctivitis, or failure to improve after initial 5-7 day course 1

Special considerations:

• Gonococcal conjunctivitis: Marked lid edema, severe purulent discharge, preauricular lymphadenopathy—requires systemic antibiotics (hospitalization for parenteral therapy), daily follow-up until resolution, and treatment of sexual contacts 1
• Chlamydial conjunctivitis: Follicular conjunctivitis with chemosis and mucopurulent discharge—requires systemic therapy (oral azithromycin 1g single dose or doxycycline 100mg BID for 7-14 days), evaluation of sexual partners, and screening for other STIs 1, 5

Allergic Conjunctivitis

Topical antihistamines with mast cell-stabilizing activity are first-line treatment. 1

• First-line agents: Olopatadine or ketotifen 1
• Environmental modifications: Wear sunglasses as barrier to airborne allergens, use cold compresses and refrigerated artificial tears, avoid eye rubbing 1
• Refractory cases: Short-term corticosteroids (1-2 week course with low side-effect profile) may be necessary 1
• Allergen-specific immunotherapy: Beneficial in reducing symptoms, particularly in children 1

Chronic/Refractory Cases

If bilateral redness and discharge persist despite appropriate treatment, stop all topical antibiotics immediately and reconsider the diagnosis. 5

• Prolonged topical antibiotic use promotes resistant organisms 5
• Consider alternative diagnoses: Chronic blepharitis/blepharokeratoconjunctivitis, chlamydial infection (requires systemic antibiotics), or underlying autoimmune/inflammatory condition 5, 4
• Chronic blepharitis management: Comprehensive eyelid hygiene with warm compresses, gentle lid margin cleansing, topical erythromycin or bacitracin ointment 5

Follow-Up Recommendations

• Viral conjunctivitis: Re-evaluate within 1 week if severe; return if symptoms persist beyond 2-3 weeks 1, 6
• Bacterial conjunctivitis: Return if no improvement after 5-7 days of appropriate antibiotics 1
• Patients on topical corticosteroids: Regular monitoring of IOP and periodic pupillary dilation required 1, 6
• Chronic blepharitis: Reassess in 2-4 weeks 5

Critical Pitfalls to Avoid

• Never use topical corticosteroids without ophthalmology follow-up—they can prolong adenoviral infections, worsen HSV infections, elevate IOP, and cause cataracts 1
• Do not confuse subepithelial infiltrates (occur 1+ weeks after adenoviral conjunctivitis) with HSV epithelial keratitis—corticosteroids are contraindicated in active HSV 6
• Avoid contact lens wear during any infectious conjunctivitis 1
• Do not miss gonococcal conjunctivitis—it can cause corneal perforation and requires immediate systemic treatment 1
• Chronic/recalcitrant conjunctivitis may indicate underlying malignancy (sebaceous or squamous cell carcinoma) and requires further evaluation 1