Attachment to and penetration of conventional and silicone hydrogel contact lenses by Fusarium solani and Ulocladium sp. in vitro

Abstract

Purpose: To analyze the relative capacities of Fusarium solani and Ulocladium sp. to attach to and penetrate silicone hydrogel soft contact lenses.

Methods: Representative silicone hydrogel (SH, siloxy complexes) and conventional [hydroxyethylmethylacrylate (HEMA)] soft contact lenses were exposed to suspensions of F. solani and Ulocladium sp. in vitro (10 conidia/mL in phosphate-buffered saline). The lenses were incubated with shaking at ambient temperatures and examined after rinsing in a multipurpose contact lens solution (MPS) by light and scanning electron microscopy.

Results: Isolates of both genera firmly attached to and penetrated both lens types, but Ulocladium sp. did so in greater density and more rapidly than F. solani. The extent of firm attachment and time needed for penetration into the lenses varied with strain and substratum, particularly with the isolates of F. solani. Morphologic characteristics (eg, penetration pegs, microcycle conidiation, and chlamydospores) of F. solani in the SH and HEMA lenses were similar to those observed in several lenses from patients with ReNu with MoistureLoc (RML)-associated Fusarium keratitis.

Conclusions: To our knowledge, this is the first report that F. solani produces coiled penetration pegs in the matrices of SH hydrophilic soft contact lenses similar in morphology to those found in HEMA lenses. F. solani attaches firmly to SH lenses and rarely penetrates the lens matrix, but viable fungal propagules may remain on the lens after vigorous rinsing with MPS. Failure to use a manual cleaning-disinfection procedure may help to explain the increased incidence of Fusarium keratitis associated with contact lens wear.