What are the causes and treatments for red eyes?

Red Eyes: Causes and Treatment

Red eye is most commonly caused by conjunctivitis (viral, bacterial, or allergic), but requires systematic evaluation to identify sight-threatening conditions including keratitis, iritis, acute glaucoma, and corneal ulceration that demand urgent ophthalmology referral. 1, 2

Immediate Red Flags Requiring Emergency Ophthalmology Referral (<24 hours)

Use the RAPID acronym to identify emergencies 1:

• Redness with any other red flag feature
• Acuity loss (decreased vision)
• Pain (moderate to severe, not just irritation)
• Intolerance to light (photophobia)
• Damage to cornea (fluorescein uptake, ulceration, haze, opacity, purulent discharge)

Additional urgent referral criteria include 2, 3:

• Corneal involvement or infiltrates
• History of herpes simplex virus eye disease
• Immunocompromised status
• Lack of response to appropriate therapy
• Recurrent episodes
• Conjunctival scarring

Common Causes by Clinical Presentation

Viral Conjunctivitis

Clinical features 2, 3:

• Watery discharge (not purulent)
• Follicular reaction on inferior tarsal conjunctiva
• Preauricular lymphadenopathy
• Often starts unilateral, becomes sequentially bilateral
• Concurrent upper respiratory infection common
• Self-limited, resolves in 5-14 days

Treatment 3:

• No antibiotics (provide no benefit and may cause toxicity)
• Artificial tears and cold compresses for symptomatic relief
• Topical antihistamines for symptom control
• Patient education: highly contagious for 10-14 days; strict hand hygiene, avoid sharing towels/pillows
• Topical corticosteroids only for severe cases (marked chemosis, membranous conjunctivitis) with close ophthalmology follow-up for IOP monitoring

Bacterial Conjunctivitis

Clinical features 2:

• Mucopurulent discharge with matted eyelids
• Papillary (not follicular) reaction
• May be unilateral or bilateral
• Preauricular lymphadenopathy less common unless hypervirulent organisms

Treatment 2, 4:

• Mild cases: often self-limited, may resolve without treatment
• Moderate to severe: 5-7 day course of broad-spectrum topical antibiotic (e.g., moxifloxacin 0.5% one drop three times daily for 7 days)
• No specific antibiotic superior; choose based on convenience and cost
• MRSA increasingly isolated but fluoroquinolones remain effective

Special considerations 2:

• Gonococcal conjunctivitis: requires systemic treatment plus topical therapy; can cause corneal perforation
• Chlamydial conjunctivitis: requires systemic treatment and evaluation of sexual partners

Allergic Conjunctivitis

Clinical features 2:

• Itching is the most consistent distinguishing feature
• Bilateral presentation
• Watery discharge
• No preauricular lymphadenopathy
• Seasonal or perennial pattern

Treatment 1, 2:

• Environmental modifications: sunglasses as allergen barrier, cold compresses, refrigerated artificial tears, avoid eye rubbing
• First-line: topical antihistamines with mast cell-stabilizing activity
• Avoid chronic vasoconstrictor use (causes rebound vasodilation)
• Refractory cases: brief 1-2 week course of low side-effect profile topical corticosteroids
• Severe cases: consider topical cyclosporine or tacrolimus 1

Critical Management Principles

Avoid indiscriminate use of medications 1, 2:

• Topical antibiotics cause toxicity in viral conjunctivitis without benefit
• Corticosteroids prolong adenoviral infections and worsen HSV infections
• Corticosteroids can increase intraocular pressure and cause cataracts

Contact lens considerations 2:

• Avoid contact lens wear during any infectious conjunctivitis
• Giant papillary conjunctivitis in lens wearers requires appropriate lens care and frequent replacement

Unilateral vs bilateral redness 1:

• Bilateral redness typical in most conjunctivitis
• Unilateral redness should prompt consideration of other serious causes (keratitis, iritis, acute glaucoma, foreign body)

Infection Control for Viral Conjunctivitis

Patient instructions 3:

• Minimize contact with others for 10-14 days
• Strict hand hygiene with soap and water
• Avoid sharing towels, pillows, personal items
• Disinfect surfaces with EPA-registered hospital disinfectant

Healthcare setting 1:

• Consider triaging to dedicated "red-eye room" during epidemics
• Defer IOP measurement unless absolutely necessary
• Disinfect tonometer tips with 1:10 sodium hypochlorite solution
• Use disposable tonometer tips or coverlets when available

Follow-Up Recommendations

Viral conjunctivitis 3:

• Severe cases: re-evaluate within 1 week
• Patients not on corticosteroids: return if symptoms persist beyond 2-3 weeks
• Patients on corticosteroids: regular IOP monitoring and pupillary dilation

Bacterial conjunctivitis 2:

• Return if no improvement after 5-7 days of antibiotics
• Consider culture and alternative antibiotic if treatment failure

Common Pitfalls to Avoid

• Prescribing antibiotics for viral conjunctivitis 2, 3
• Using topical corticosteroids without ophthalmology supervision 1, 2
• Missing sight-threatening conditions by not checking for red flags 1, 2
• Inadequate patient education about viral contagiousness 3
• Allowing contact lens wear during infectious conjunctivitis 2
• Failing to recognize chronic/recalcitrant conjunctivitis may indicate underlying malignancy (sebaceous or squamous cell carcinoma) 2