Acanthamoeba Keratitis

A. Acanthamoeba - free-living amoeba found in trophozoite or cyst form

B. Can be removed in either form by thorough cleaning; however, the cyst form may invade the lens.

C. To avoid Acanthamoeba:

- Practice proper lens care and hygiene!
- Adhere to prescribed wearing schedule
- Do not wear lenses while swimming, in hot tubs or spas
- Wash hands thoroughly before handling lens
- Never use tap water, distilled water or saliva on lenses
- Use sterile contact lens saline solution
- Avoid homemade saline
- Clean and disinfect lenses on removal according to the manufacturers' recommended instructions. Store for the recommended amount of time.
- Rinse lenses with sterile saline prior to insertion
- Use sterile saline to dissolve enzymatic tablets
- Never instill non-sterile saline directly in the eye
- Rinse case daily with sterile saline or disinfecting solution and allow to air dry

D. Acanthamoeba is killed by heat disinfection and 2 step hydrogen peroxide disinfection if left over 4 hours. If standard solution regimens are used according to manufacturer's instructions, they are effective.

E. Symptoms:

1. Severe pain (doesn’t correspond to early clinical findings)
2. Light sensitivity
3. Vision loss
4. Take a good case history to determine if they fall in one of the predisposing conditions (i.e., homemade saline use, trauma, etc.)

F. Signs:

1. Conjunctival injection
2. Radial neurokeratitis (radial infiltrates along the corneal nerves) Sometimes misdiagnosed as stromal herpes simplex
3. Ring infiltrate/ulcer of the stroma
4. Stromal keratitis

G. Lab tests

1. Calcofluor white (fluorescence), Corneal biopsy/scrapings

H. Treatment

Neomycin
Brolene 0.1% drops
Brolene ointment
Clotrimazole (broad spectrum anti-fungal)
Miconazole
Ketoconazole
Itraconazole

I. If unsuccessful; penetrating keratoplasty (Usually long-term prognosis)