In a 25‑year‑old man presenting with a red, swollen eye with crusty discharge, itching, and pain, what is the most likely diagnosis and recommended treatment?

Diagnosis and Treatment of Red, Swollen, Crusty, Itchy, Painful Eye in a 25-Year-Old Male

Most Likely Diagnosis

This presentation is most consistent with bacterial conjunctivitis, though blepharitis should also be strongly considered given the combination of crusting, swelling, and pain. 1, 2

The key distinguishing features pointing toward bacterial conjunctivitis include:

• Mucopurulent discharge with crusting (matted eyelids) is the hallmark of bacterial rather than viral conjunctivitis 1, 2, 3
• Pain is more commonly associated with bacterial infection, whereas viral conjunctivitis typically causes irritation without significant pain 1, 4
• Swelling can occur with bacterial conjunctivitis, particularly in moderate to severe cases 1
• Itching is less typical for pure bacterial conjunctivitis and raises the possibility of concurrent blepharitis or an allergic component 1

However, the combination of crusting, swelling, and itching strongly suggests anterior blepharitis, which commonly coexists with or mimics conjunctivitis. 1 Blepharitis is associated with the same ocular surface pathogens (coagulase-negative Staphylococcus, S. aureus, Streptococcus species) that cause bacterial conjunctivitis. 1

Critical Red Flags Requiring Immediate Ophthalmology Referral

Before initiating treatment, urgently refer to ophthalmology if any of the following are present: 1, 2

• Visual loss or decreased vision
• Moderate to severe pain not relieved by topical anesthetics
• Corneal involvement (opacity, infiltrate, or ulceration on slit-lamp examination)
• Severe purulent discharge (copious, suggesting gonococcal infection)
• History of herpes simplex virus eye disease
• Recent ocular surgery
• Immunocompromised state
• Lack of response to therapy after 3-4 days

In a sexually active 25-year-old male with severe purulent discharge, gonococcal conjunctivitis must be excluded, as it can cause corneal perforation and requires immediate systemic antibiotic therapy. 1, 2

Recommended Treatment Approach

For Bacterial Conjunctivitis (Mild to Moderate)

Prescribe a 5-7 day course of broad-spectrum topical antibiotic, choosing the most convenient or least expensive option, as no specific antibiotic has proven superiority: 1, 2

• Erythromycin 0.5% ointment applied to the eyelid margins 2-4 times daily, OR
• Polymyxin B/trimethoprim drops 1 drop 4 times daily, OR
• Fluoroquinolone drops (ofloxacin, ciprofloxacin, moxifloxacin) 1 drop 4 times daily 5

Note: While mild bacterial conjunctivitis is often self-limited (55.5% spontaneous resolution by days 4-9), antibiotics increase clinical cure by 26% and reduce persistent infection by 27%. 1, 6 Topical antibiotics provide earlier clinical and microbiological remission, particularly in days 2-5 of treatment. 1, 6

For Concurrent Blepharitis (Given Crusting and Itching)

The patient must understand that blepharitis cure is usually not possible, and treatment is aimed at symptom control. 1 Initiate the following regimen: 1

1. Warm compresses for several minutes to soften crusts and warm meibomian secretions—use a clean washcloth with hot tap water (not scalding) 1

2. Eyelid cleansing after warm compresses:

   • Gently massage the eyelid margins from side to side to remove crusting from eyelashes 1
   • Use diluted baby shampoo or commercially available eyelid cleaner (hypochlorous acid 0.01% has strong antimicrobial effect) on a cotton swab or clean fingertip 1
   • Perform this regimen once or twice daily, at a time convenient for the patient 1

3. Topical antibiotic ointment (bacitracin or erythromycin) applied to the eyelid margins once or more times daily 1

This eyelid hygiene regimen may be required long-term, as symptoms often recur when treatment is discontinued. 1

Differential Diagnosis Considerations

Viral Conjunctivitis (Less Likely)

Viral conjunctivitis typically presents with: 1, 2

• Watery discharge (not mucopurulent/crusty) 2, 3
• Follicular reaction on inferior tarsal conjunctiva 2
• Preauricular lymphadenopathy 1, 2
• Often preceded by upper respiratory infection 1, 2
• Usually starts unilateral, becomes sequentially bilateral 2

If viral conjunctivitis is suspected, do NOT prescribe antibiotics, as they provide no benefit and may cause unnecessary toxicity. 2 Treatment is supportive only: artificial tears, cold compresses, and topical antihistamines for symptomatic relief. 2

Allergic Conjunctivitis (Less Likely)

Allergic conjunctivitis is characterized by: 1, 2

• Itching as the predominant and most distinguishing symptom 2
• Bilateral presentation 2
• Watery discharge with mild mucous component 2
• History of atopy, asthma, or eczema 2
• Absence of matted eyelids 2

If allergic features dominate, treat with topical antihistamines with mast cell-stabilizing activity (olopatadine or ketotifen) as first-line therapy. 2

Follow-Up and Patient Education

• Instruct the patient to return in 3-4 days if no improvement 1
• Emphasize strict hand hygiene with soap and water to prevent transmission to the unaffected eye or others 2
• Avoid sharing towels, pillows, or personal items 2
• Discontinue contact lens wear during any infectious conjunctivitis 2
• For blepharitis, counsel that daily or several-times-weekly eyelid cleansing is often required long-term to control chronic symptoms 1

Common Pitfalls to Avoid

• Do not prescribe antibiotics indiscriminately for viral conjunctivitis, as this contributes to resistance and causes unnecessary side effects 2
• Do not use topical corticosteroids without ophthalmology consultation, as they can prolong adenoviral infections, worsen HSV infections, and cause increased intraocular pressure and cataracts 2
• Do not miss gonococcal conjunctivitis in sexually active adults—if severe purulent discharge is present, obtain conjunctival cultures and Gram stain, and initiate systemic antibiotic therapy immediately 1, 2
• In patients with advanced glaucoma, advise against aggressive eyelid pressure during warm compress treatment, as it may increase intraocular pressure 1
• Do not assume bacterial conjunctivitis if itching is the predominant symptom—this suggests allergic conjunctivitis, which will not respond to antibiotics 2