What is the appropriate work‑up and management for a patient presenting with a bright red eye?

Bright Red Eye: Work-Up and Management

For a patient presenting with a bright red eye, immediately assess for vision loss, severe pain, corneal opacity, or severe purulent discharge—any of these red flags mandates same-day ophthalmology referral; otherwise, determine whether the presentation suggests subconjunctival hemorrhage (painless, well-demarcated blood without discharge) versus conjunctivitis (discharge, irritation, injection) and manage accordingly. 1, 2, 3

Immediate Red Flag Assessment

Perform a focused evaluation to identify sight-threatening conditions requiring urgent ophthalmology consultation within 24 hours:

• Visual loss or decreased visual acuity 1, 2, 3
• Moderate to severe ocular pain (beyond mild irritation) 1, 2, 3
• Corneal involvement (opacity, loss of transparency, visible infiltrate) 1, 2, 3
• Severe purulent discharge (especially if unilateral, suggesting gonococcal infection) 1, 2, 3
• History of herpes simplex virus eye disease 1, 2, 3
• Immunocompromised status 1, 2, 3
• Recent ocular surgery or trauma 2, 3
• Contact lens wear (raises concern for bacterial keratitis) 1, 2

Distinguish Subconjunctival Hemorrhage from Conjunctivitis

Subconjunctival Hemorrhage

• Painless, well-demarcated bright red blood beneath the conjunctiva without discharge 4, 5
• Vision remains normal, no photophobia 4, 5
• Typically benign and self-resolving within 1-2 weeks 4, 5
• Reassure the patient and recommend follow-up only if recurrent or associated with trauma 4, 5

Conjunctivitis (if discharge or diffuse injection present)

Proceed with detailed history and examination below.

Detailed History for Conjunctivitis

Discharge Characteristics

• Watery discharge suggests viral or allergic conjunctivitis 1, 3
• Mucopurulent or purulent discharge with matted eyelids indicates bacterial conjunctivitis 1, 3
• Absence of discharge makes bacterial conjunctivitis less likely 2

Symptom Pattern

• Itching as predominant symptom strongly suggests allergic conjunctivitis 1, 3
• Absence of itching favors infectious etiology 1
• Worsening in morning typical of blepharitis 6
• Worsening later in day typical of dry eye 6

Laterality and Onset

• Unilateral presentation should prompt consideration of herpes simplex virus, bacterial infection, or corneal pathology 2, 3
• Abrupt onset, initially unilateral but becoming sequentially bilateral is characteristic of viral conjunctivitis 1, 3
• Bilateral presentation more common in viral, allergic, or dry eye 3

Associated Features

• Concurrent upper respiratory infection favors viral conjunctivitis 1, 3
• Recent close contact with conjunctivitis suggests viral etiology 1
• Seasonal or environmental triggers suggest allergic conjunctivitis 2, 3
• History of atopy, asthma, or eczema supports allergic conjunctivitis 1, 3
• Recent sexual activity or genitourinary symptoms raises concern for gonococcal or chlamydial conjunctivitis 1

Physical Examination

External Inspection

• Preauricular lymphadenopathy suggests viral (especially adenoviral) conjunctivitis 1, 3
• Marked eyelid edema with copious purulent discharge indicates gonococcal conjunctivitis—a vision-threatening emergency 1, 3
• Vesicular rash or ulceration of eyelids suggests herpes simplex virus 1

Conjunctival Examination

• Follicular reaction (small dome-shaped elevations on inferior tarsal conjunctiva) indicates viral conjunctivitis 1, 3
• Papillary reaction suggests bacterial or allergic conjunctivitis 1, 3
• Conjunctival scarring or pseudomembrane are red flags requiring urgent referral 1, 3

Corneal Assessment

• Any corneal opacity, infiltrate, or ulceration constitutes an emergency requiring immediate ophthalmology referral 1, 3
• Clear cornea strongly suggests conjunctivitis rather than keratitis 1

Management by Etiology

Viral Conjunctivitis (Most Common)

Viral conjunctivitis is self-limited (resolving in 5-14 days) and does not respond to antibiotics; treatment is supportive only. 1, 2

• Avoid topical antibiotics—they provide no benefit and may cause unnecessary toxicity 1, 2, 3
• Prescribe preservative-free artificial tears 4 times daily for symptomatic relief 1, 2
• Recommend cold compresses to reduce swelling and discomfort 1
• Patient education is critical: emphasize hand hygiene (wash with soap and water), avoid sharing towels/pillows, and limit close contact for 10-14 days from symptom onset 1
• Do not prescribe topical corticosteroids without ophthalmology supervision—they can prolong adenoviral infection, worsen herpes simplex keratitis, and increase intraocular pressure 1, 3
• Re-evaluate if symptoms persist beyond 2-3 weeks or worsen 1

Bacterial Conjunctivitis

• Mild cases often resolve without treatment, but topical antibiotics may shorten duration and enable earlier return to work/school 1
• For moderate to severe cases, prescribe a 5-7 day course of broad-spectrum topical antibiotic 1, 7
• No single antibiotic is superior; choose the most convenient or cost-effective option 1:
  • Erythromycin ointment
  • Polymyxin B/trimethoprim drops
  • Fluoroquinolone (e.g., moxifloxacin 0.5% one drop three times daily for 7 days) 7
• Obtain cultures only in high-risk situations: neonatal conjunctivitis, suspected gonococcal infection, recurrent/severe/chronic purulent conjunctivitis, or failure to improve after 5-7 days 1

Gonococcal Conjunctivitis (Vision-Threatening Emergency)

Gonococcal conjunctivitis can cause corneal perforation within 24 hours if untreated; immediate systemic therapy is mandatory. 1, 3

• Administer ceftriaxone 250 mg intramuscularly (single dose) plus azithromycin 1 g orally (single dose) 1
• Add topical antibiotic therapy 1, 3
• Hospitalize for parenteral therapy and daily ophthalmology follow-up until resolution 1
• Treat sexual contacts and evaluate for other sexually transmitted infections 1

Chlamydial Conjunctivitis

• Requires systemic antibiotic therapy—topical treatment alone is insufficient 1, 2, 3
• Evaluate and treat sexual partners 1, 2, 3
• Confirm diagnosis with PCR or immunofluorescent antibody testing 1

Allergic Conjunctivitis

• First-line: topical antihistamines with mast cell-stabilizing activity (e.g., olopatadine or ketotifen, one drop twice daily) 1, 2
• Environmental modifications: wear sunglasses as allergen barrier, use cold compresses, apply refrigerated artificial tears, avoid eye rubbing 1
• For refractory cases, consider short-term (1-2 week) low-potency topical corticosteroid (e.g., loteprednol) with baseline and periodic intraocular pressure monitoring 1, 2

Follow-Up and Monitoring

• Bacterial conjunctivitis: re-evaluate if no improvement after 5-7 days of antibiotics 1
• Viral conjunctivitis: return if symptoms persist beyond 2-3 weeks or worsen 1
• Severe viral conjunctivitis with corneal involvement: re-evaluate within 1 week 1
• Patients on topical corticosteroids: regular intraocular pressure monitoring and periodic pupillary dilation 1, 2

Common Pitfalls to Avoid

• Do not prescribe antibiotics for viral conjunctivitis—this contributes to antimicrobial resistance and exposes patients to unnecessary adverse effects 1, 2, 3
• Do not miss gonococcal conjunctivitis—failure to recognize this emergency can lead to corneal perforation and permanent vision loss 1, 3
• Do not use topical corticosteroids without ophthalmology supervision—they can prolong adenoviral infections, exacerbate herpes simplex keratitis, elevate intraocular pressure, and accelerate cataract formation 1, 3
• Do not allow contact lens wear during any infectious conjunctivitis—this increases risk of bacterial keratitis 1
• Do not fail to counsel about contagiousness—inadequate patient education facilitates community spread 1