Fungal contamination of contact lens cases can occur despite patient compliance with proper lens handling, cleaning and replacement instructions, reports a study in the March 2015 Eye & Contact Lens.1
Researchers in Greece collected 216 samples of contact lens solution from 117 lens cases of asymptomatic lens wearers; 194 were collected from two-cup storage cases (TCSC) filled with non-hydrogen peroxide-containing solutions, four from TCSCs with a hydrogen peroxide solution and 36 from single-cup storage cases (SCSC) containing hydrogen peroxide solutions. All subjects were using monthly disposable hydrogel, low water content soft lenses on a daily wear basis and were required to comply with lens cleaning, handling and replacement instructions given by the manufacturer or attending optometrist in order to participate in the study.
After culturing the collected lens solution samples, researchers identified the presence of fungi from 15 cultures obtained from 12 storage cases. Seven molds (one Fusarium solani, four Aspergillus niger and two Aspergillus fumigatus), seven yeasts (five Candida parapsilosis, one Candida tropicalis and one Rhodotorula rubra) and one a mold in combination with a yeast (F. solani with Candida guilliermondii) were discovered. Interestingly, the peroxide group had a higher rate of fungal isolation compared with the multipurpose solution group, likely due to quick neutralization, selection of naturally resistant microbes adapted to survive repeated peroxide use and biofilm release of catalase that neutralizes peroxide.
These results are concerning, say the researchers, because “even when contact lens users report compliance with instructions of contact lens handling cleaning and replacement, it is still possible to have microbial contamination of the stock solutions that may lead to corneal infection.” They say that further improvement of contact lens disinfectant solutions and lens hygiene education is needed.
Another study suggests topical amphotericin B (AMB) and natamycin may be particularly effective against certain fungi—specifically, the Candida species.2 Researchers exposed samples of 68 Candida isolates (37 albicans and 31 non-albicans) to AMB 0.2%, natamycin 5%, voriconazole 1% and fluconazole 0.2%, examined for growth after 48 hours and found 100% of the Candida isolate samples mixed with AMB 0.2% and natamycin 5% demonstrated growth inhibition, suggesting that both AMB and natamycin have been shown in this study to be more effective than the other agents tested.
1. Mela EK, Anastassiou ED, Gartaganis SP, Christofidou M. Fungal isolation from disinfectant solutions of contact lens storage cases among asymptomatic users. Eye & Contact Lens. 2015 Mar;41(2):87-90.
2. Spierer O, Dugar J, Miller D, O’Brien TP. Comparative antifungal susceptibility analysis of candida albicans versus non-albicans candida corneal isolates. Cornea. 2015 May;34(5):576-579.