• Cornea/External Disease

    This experimental laboratory study evaluated in vitro the amoebicidal effects of riboflavin and ultraviolet A (UVA) collagen cross-linking on two strains of Acanthamoeba species. The authors report in the March issue of the American Journal of Ophthalmology that a single 30- or 60-minute cross-linking dose did not eradicate either environmental Acanthamoeba species 65 or pathogenic Acanthamoeba species 7376. However, they conclude that a single 60-minute dose may reduce Acanthamoeba growth and a longer exposure could achieve the desired effect.

    The two Acanthamoeba species were tested identically under four treatment conditions: 0.1% riboflavin and 30 minutes of UVA irradiation, 0.1% riboflavin and 60 minutes of UVA irradiation, no riboflavin and no UVA exposure, and 0.1% riboflavin and no UVA exposure.

    In all cases, cysts and trophozoites were detected 24 hours after treatment at a radial distance from the center of the seeding point of more than 5 mm, indicating that the amoebae were viable. All treated and untreated groups of amoebae from the two strains exhibited growth. The final morphologic features of the two strains of trophozoites that received treatment were similar to those of the initial seeding group and the untreated control group.

    The authors say while a single dose of 30- or 60-minute UVA exposure (3 mW/cm2, 370 nm) does not appear effective for eradication of Acanthamoeba, the observed degradation of some cysts suggests that reduction is possible. They note that while a longer treatment period may be effective at eradication, currently longer doses are not advisable because of their collateral effects.

    They conclude that since in vitro results may not indicate in vivo efficacy, future studies should test the validity of this treatment for Acanthamoeba keratitis.