A contact‑lens wearer presents with new photophobia and watery eye discharge; what is the most likely diagnosis and immediate management?

Contact Lens-Related Microbial Keratitis

The most likely diagnosis is bacterial keratitis, and immediate management requires discontinuing contact lens wear immediately, performing fluorescein staining to assess for corneal involvement, and initiating broad-spectrum topical antibiotic therapy targeting Pseudomonas aeruginosa if any corneal epithelial defect is present. 1, 2

Most Likely Diagnosis

Bacterial keratitis is the primary concern in any contact lens wearer presenting with photophobia and watery discharge, as this represents the most serious sight-threatening complication of contact lens wear. 3

• Pseudomonas aeruginosa is the most commonly isolated organism in contact lens-associated infections and adheres readily to contact lens deposits. 3, 2, 4
• The combination of photophobia (indicating corneal involvement) and contact lens use creates high suspicion for infectious keratitis rather than simple conjunctivitis. 1, 5
• Overnight wear increases the risk of microbial keratitis 5-fold compared to daily wear (21 vs. 4 per 10,000 persons annually). 3, 2

Critical Red Flags to Assess

• Pain severity: Moderate to severe pain suggests bacterial keratitis or Acanthamoeba keratitis, particularly with water exposure history (swimming, showering, hot tubs while wearing contacts). 1, 6
• Unilateral vs bilateral presentation: Unilateral presentation with pain is more concerning for infectious keratitis than bilateral allergic or viral conjunctivitis. 1
• Visual acuity changes: Any decrease in vision elevates concern for corneal involvement. 5

Immediate Management Algorithm

Step 1: Remove Contact Lenses Immediately

• Discontinue all contact lens wear immediately and instruct the patient not to resume until complete resolution occurs. 1
• This is mandatory regardless of suspected etiology—failure to discontinue lens wear leads to prolonged infection and complications. 1

Step 2: Perform Slit Lamp Examination with Fluorescein Staining

• Examine the cornea carefully with fluorescein staining to identify any epithelial defects, infiltrates, or ulceration. 1, 5
• Missing keratitis by treating as simple conjunctivitis is a critical pitfall that can result in permanent vision loss. 1

Step 3: Initiate Topical Antibiotic Therapy

• All contact lens wearers with suspected bacterial involvement require topical antibiotic therapy, unlike non-contact lens wearers where observation may be appropriate, due to the increased risk of bacterial keratitis. 1
• Topical fluoroquinolones (ciprofloxacin) or aminoglycosides (gentamicin) are first-line agents, as isolated bacteria show highest sensitivity to these classes. 4
• Broad-spectrum coverage targeting Pseudomonas is essential given its predominance in contact lens-related infections. 3, 4

Step 4: Consider Acanthamoeba Keratitis

• Suspect Acanthamoeba if moderate or severe pain is present, especially with history of swimming, showering, or hot tub use while wearing contacts. 1, 6
• Acanthamoeba presents with dendriform epithelial patterns and requires specialized treatment—missing this diagnosis can cause permanent vision loss. 1, 6
• Tap water or distilled water use in contact lens care regimens is a major risk factor. 6

Differential Considerations

While bacterial keratitis is the primary concern, other contact lens-related conditions to consider include:

• Contact lens-related keratoconjunctivitis: Presents with diffuse conjunctival injection, superficial punctate keratopathy, and variable papillary hypertrophy, but typically has subacute onset without severe photophobia. 3
• Giant papillary conjunctivitis: Characterized by mucoid discharge and papillary hypertrophy of superior tarsal conjunctiva, with chronic gradual symptom onset rather than acute photophobia. 3

Follow-Up Management After Acute Phase

Once the acute infection resolves:

• Review contact lens practices comprehensively, including lens type, fit, wearing schedule, cleaning/disinfection regimen, and water exposure habits. 1
• Switch to daily disposable lenses to reduce infection risk from lens deposits and contaminated cases. 1
• Strongly discourage overnight wear, as it increases corneal infection risk fivefold even with FDA-approved extended-wear lenses. 3, 1
• Educate on water avoidance: Never swim, shower, use hot tubs, or wash hair while wearing contact lenses due to Acanthamoeba risk. 1, 7
• Replace contact lens cases at least every 3 months to prevent contamination. 1, 7
• Never rinse lenses or cases with tap water, bottled water, or homemade saline—this is a critical source of Acanthamoeba contamination. 1, 7

Common Pitfalls to Avoid

• Treating as simple conjunctivitis without corneal examination: Failing to perform fluorescein staining can miss sight-threatening keratitis. 1
• Allowing continued contact lens wear during treatment: This prolongs infection and increases complication risk. 1
• Resuming contact lens wear too early: Lenses should not be worn until complete resolution is confirmed by examination. 1
• Missing Acanthamoeba in patients with pain and water exposure: This requires different treatment than bacterial keratitis and has worse visual outcomes if delayed. 1, 6