IT HAS BEEN APPROXIMATED that 99% of individuals who wear contact lenses report at least one contact lens hygiene risk behavior (Jones et al, 2023). The most serious complication for individuals who wear contact lenses is microbial keratitis, with an infection rate of 4 to 6 per 10,000 (Hsiao et al, 2018). When all modalities of contact lenses are included, the risk of vision loss due to microbial keratitis related to contact lens wear is between 0.3 and 0.9 per 10,000 wearers (Hsiao et al, 2018).
The contact lens storage case is often associated with microbial contamination. In fact, contamination is present in up to 80% of cases (Mendonca et al, 2023). The most common organisms of contamination are gram-positive bacteria, followed by gram-negative bacteria and then fungi (Mendonca et al, 2023). Contact lens case contamination due to infrequent cleaning and case replacement has been recognized as one of the primary risk factors for microbial keratitis (Jones et al, 2023; Mendonca et al, 2023).
Other unsafe practices that can lead to microbial keratitis are sleeping in lenses, topping off solutions, and exposure to tap water. Annually, 1 million visits occur in the U.S. for keratitis or other contact lens-related complications, with an annual estimated cost of $175 million (Jones et al, 2023).
The type of contact lens disinfection solution a patient uses can modify the profile and frequency of microbes found in a contact lens storage case (Mendonca et al, 2023). There are various potential sources of ocular contamination, including the adhesion and colonization of bacteria and fungi microorganisms on contact lenses, storage cases, and ancillary devices, such as application and removal devices for rigid GP contact lenses.
Microorganisms form a biofilm on a colonized surface and appear as adhesion to the surface and/or adhesion among the microorganisms themselves. A biofilm may be a risk factor to develop a corneal infection related to contact lens wear.
A study tested 14 different multipurpose contact lens solutions on mature biofilms comprising Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens, and Candida albicans (Mendonca et al, 2023). The biofilms were created in the contact lens cases and solutions were added 24 hours later. The minimum disinfection times were used, as suggested by the manufacturers.
The activity against planktonic and sessile cells was assessed and quantified as colony-forming units per milliliter. Biofilm eradication was defined as a 99.9% reduction in viable cells. The majority of solutions demonstrated activity against planktonic cells. A significant reduction in the S. marcescens biofilm was exhibited in 5 of the 14 solutions. The minimal eradication biofilm concentration was only attained for S. marcescens. None of the solutions successfully eradicated the minimal biofilm extinction of S. aureus, P. aeruginosa, or C. albicans.
An important aspect of multipurpose contact lens solution activity is the exposure time to the solution. In a different study, multipurpose contact lens solutions were tested against P. aeruginosa, S. aureus, and C. albicans (Dosler et al, 2020). Biofilms were evaluated at various time points during multipurpose contact lens solution exposure. Only one brand demonstrated a 3-log unit reduction for contact lens biofilm after six hours. Thus, an exposure time of less than six hours is insufficient to eradicate a biofilm of bacteria or fungi from contact lenses.
These studies emphasize the importance of educating our patients on the proper care of contact lenses, contact lens cases, and ancillary supplies. CLS
REFERENCES
1. Jones L, Efron N, Bandamwar K, et al. TFOS Lifestyle: Impact of contact lenses on the ocular surface. Ocul Surf. 2023 Jul;29:175-219.
2. Hsiao YT, Fang PC, Chen JL, et al. Molecular bioburden of the lens storage case for contact lens-related keratitis. Cornea. 2018;37:1542-1550.
3. Mendonca JR, Dantas LR, Tuon FF. Activity of multipurpose contact lens solutions against Staphylococcus aureus, Pseudomonas aeruginosa, Serratia marcescens and Candida albicans biofilms. Ophthalmic Physiol Opt. 2023 Sep;43:1092-1099.
4. Dosler S, Hacioglu M, Yilmaz FN, Oyardi O. Biofilm modelling on the contact lenses and comparison of the in vitro activities of multipurpose lens solutions and antibiotics. PeerJ. 2020 Jun 24;8:e9419.
