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 (doesnt 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)