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Clinical Presentation
- Slow, often protracted course; frequently several week long history
- Typically associated with contact lenses (especially when swimming or cleaning under tap water)
- Dendritiform corneal lesions + contact lenses = Acanthamoeba until proven otherwise!
- Ring infiltrate + severe pain with missed/late diagnosis
- Epithelial pseudodendrites, perineural infiltrates
Work-up
- Large corneal abrasion for specimen collection with a hockey knife and tetracaine (few Acanthamoebas in the epithelium), also therapeutic effect by removing any Acanthamoebas + better penetration
- Consider sending in contact lens for culture
- Confocal microscopy (with Z-ring): Cysts?
Treatment
- Initiate therapy only after a confirmed diagnosis; no immediate therapy needed!
- Administer consistent therapy without interruption, if not possible logistically it is better to wait 1-2 days before starting
- Trophozoites can transform into cysts in about 48 hours (after starting therapy) – cysts are much more difficult to treat!
- Mandatory hospitalisation for therapy, including effective pain management! Outpatient treatment is usually not viable!
- Before starting therapy: consider repeating extensive abrasion for better drug penetration
- Therapy options:
- Combination of
- Brolene 0.1% gtt hourly, day and night, for 3 days
- PHMB 0.02% gtt hourly, day and night, for 3 days
- Alternatively to PHMB: Chlorhexidine gtt hourly
- Then reduce frequency to every 2 hours during the day and every 4 hours at night for an additional 4-7 days (different reduction scheme possible depending on clinical presentation)
- Then 3-4 times daily for a minimum of 4 months, usually 6-12 months
- Combination therapy is crucial: Brolene 0.1% topical acts only on trophozoites, PHMB/Chlorhexidine act on both trophozoites and cysts!
- Combination of
- consider cycloplegia (Atropine 1% gtt 2x/day depending on anterior chamber cell flare)
- consider Flagyl or Itraconazole or Ketoconazole p.o. for advanced stages
- Steroid therapy is controversial as it increases the virulence of Acanthamoeba!
- Pain management according to the WHO pain ladder
Follow-up
- Discharge after 3 days (no clinical improvement expected at this point!)
- Possible follow-up intervals:
- 1st follow-up 4-5 days after discharge (therapy adherence?)
- 2nd follow-up after 10-14 days
- Further check-ups every 2 weeks
- After 1 month: consider reducing medications
- Note: no significant improvement is expected in the first month
- Red eye in follow-ups:
- Side effects of drops (Brolene not well tolerated) or amoebic infection?
- Diffuse superficial punctate keratitis: a sign that the patient has administered the drops as prescribed
- If suspected resistance: increase treatment frequency or dosage
- If persistent irritation after 2 months: consider differential diagnosis of immune reaction against disintegrating Acanthamoebas
- Deep corneal stroma with vascular ingrowth?
- consider initiating steroid therapy, only if the patient is highly compliant!
- Duration of therapy: usually 4-6 months up to 1 year
- Avoid corneal transplantation if possible (often requiring multiple grafts)
- At final visit: take a photo and perform a confocal microscopy for documentation in case of potential recurrence in the future
Sources
- EyeWiki Acanthamoeba Keratitis
- The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease; Nika Bagheri MD, Brynn Wajda MD, et al; Lippincott Williams&Wilkins; 7th Edition (2016)
- Kanski’s Clinical Ophthalmology: A Systematic Approach; Jack J. Kanski MD, Brad Bowling MD; Saunders Ltd.; 8th Edition (2015)