Has the introduction of multi-purpose solutions contributed to a reduced incidence of Acanthamoeba keratitis in contact lens wearers? A review.

This review paper considers hypotheses for the apparent reduction in incidence of Acanthamoeba keratitis over the last 2 years. Investigating such a reduction has been facilitated by the performance of an accurate measurement of the incidence of this infection amongst contact lens wearers in the West of Scotland at 1:6750 soft lens wearers annually in 1994 and 1995, the infection did not occur in wearers of rigid or gas permeable lenses nor in those avoiding wear of a contact lens. The reduction in frequency of presentation of this infection anecdotally in Scotland in 1996 and 1997 is supported by a retrospective survey in England, although this method of assessing incidence historically is open to error. A new survey by the Royal College of Ophthalmologists should, in due course, present another accurate incidence figure for 1997/98. The reason for the apparent decline in incidence of Acanthamoeba keratitis is believed to be due to the introduction by industry over the last 3 years of sterile multipurpose (cleaning and disinfecting) solutions (MPS) containing polyhexamethylene biguanide to achieve their current popularity. This situation is mirrored by that in the United States when the introduction of MPS is thought to have reduced their incidence rate of Acanthamoeba keratitis following the outlawing of contact lens storage in home made saline, using water contaminated with Acanthamoeba.