Ring infiltrate in a contact lens wearer who cannot attend daily
A 29-year-old man who wears monthly soft contact lenses, occasionally sleeping in them, presents with a 3-day history of a painful red left eye and photophobia. He has been using chloramphenicol ointment from a friend with no improvement. Left eye: visual acuity 6/36, IOP 14 mmHg, a 4 mm epithelial defect with a dense ring-shaped stromal infiltrate, central stromal haze, a 1 mm hypopyon and marked conjunctival injection. The contact lens was removed 2 days ago and has been discarded. Right eye is normal. He works as a lifeguard and cannot attend daily appointments easily.
1. Outline your immediate management, including investigation and empirical treatment.
Read the worked answer
Treat as sight-threatening microbial keratitis until proven otherwise.
- Take a corneal scrape at the slit lamp from the leading edge and base of the infiltrate for Gram stain, Giemsa, calcofluor white, and cultures (blood agar, chocolate agar, Sabouraud agar, and non-nutrient agar with E. coli for Acanthamoeba).
- Start empirical hourly fortified antibiotics: cefazolin 5% and tobramycin 1.5% alternating every 30 minutes, or moxifloxacin 0.5% hourly if fortified drops are unavailable.
- Add a cycloplegic (cyclopentolate 1%) for pain and to prevent synechiae; no topical steroid at this stage.
- Review daily until the epithelium is healing and the infiltrate is shrinking.
- Given his job and travel difficulty, admission is reasonable, or arrange daily review at a nearby unit with a named contact and a written plan.
2. What features would make Acanthamoeba keratitis more likely, and how would that change your treatment?
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Features suggesting Acanthamoeba:
- Pain out of proportion to signs, radial keratoneuritis, a ring infiltrate, poor response to antibacterial therapy, and a history of contact lens wear with tap water or swimming.
Investigation:
- Confocal microscopy, calcofluor white staining, and culture on non-nutrient agar.
Change in management:
- Stop or reduce antibacterials and start biguanide and diamidine therapy: polyhexamethylene biguanide 0.02% and chlorhexidine 0.02% hourly, alternating, plus propamidine 0.1% if available.
- Continue for weeks to months and taper slowly.
- Avoid steroids unless inflammation is severe and treatment is under cover.
- If medical therapy fails, consider therapeutic keratoplasty, but only after the cornea is sterilised.
3. How would you modify the plan given his job and difficulty attending daily?
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Compliance is the main determinant of outcome here.
- Admit him, or arrange supported care, because hourly drops for the first 48-72 hours are critical and he cannot attend daily from work.
- Teach and check his drop technique and involve a family member.
- Avoid fluoroquinolone monotherapy if compliance is doubtful, because inadequate dosing promotes resistance and treatment failure; fortified antibiotics with a clear written schedule are preferable.
- Give written instructions with a 24-hour contact number and a clear review plan; if he cannot comply, admission is the safer option.