Fungal isolation from disinfectant solutions of contact lens storage cases among asymptomatic users

To investigate the incidence of fungal contamination of store disinfectant solutions contained in contact lens storage cases belonging to asymptomatic contact lens users.

Asymptomatic contact lens users were asked to bring their storage cases, lenses included, without having opened the lid of the cup after placing lenses inside. The following information was recorded: age, sex, type of refractive error, contact lens material, schedule of wear, and brand of disinfectant solution. Included subjects had to comply with lens handling, cleaning, and replacement instructions given by the manufacturer or their attending optometrist. One sample per cup of contact lens case was collected using a sterile syringe. Samples were cultured on proper media for 96 hr at 35°C. Fungi were identified to species level by standard methodology.

A total of 216 samples were collected from 117 contact lens storage cases. All participants were using monthly disposable hydrogel lenses on a daily wear basis. Seven fungal species were isolated from 15 specimens (6.9%) collected from 12 storage cases (10.2%). These included one Fusarium solani, four Aspergillus niger, two Aspergillus fumigatus, five Candida parapsilosis, one Candida tropicalis, one Rhodotorula rubra, and one F. solani in combination with Candida guilliermondii. Disinfectant solutions containing hydrogen peroxide were found to be less effective than various alternative solutions in eliminating fungal species.

The results of this study show that even when contact lens users report compliance for handling, cleaning, and replacement according to the manufacturer's instructions, the potential risk of contact lens-related fungal keratitis still remains.