Abstract
Purpose: :
Contact lens care solutions are known to have toxic effects for the ocular surface. The evaluation of in vitro toxicity of contact lens care solutions is required because of its predictive value for ocular irritation in humans. ISO 10993-5 standard assesses medical devices (such as contact lens care solutions) biocompatibility through the evaluation of necrosis but needs some adjustments to better discriminate multipurpose solutions. The aim of our study was double: first, to run an interlaboratory study with French medical agency to propose adapted tools to study contact lens care solutions cytotoxicity, and second to evaluate the interest of adding a rinse step in contact lens cleaning procedure as a protection against contact lens care solutions cytotoxicity.
Methods: :
In the first place, conjunctival cells (human WKD cell line) were exposed for 30 minutes and 1 hour to neat contact lens care solutions (Optifree, Alcon; Boston Simplus, Bausch-Lomb; Renu, Bausch-Lomb; and Menicare Plus, Menicon). Cell viability was assessed using the neutral red and the alamar blue tests, and benzalkonium chloride was used as a positive control. In the second place, corneal cells (human HCE cell line) were exposed for 24 hours to contact lenses (Acuvue Advance, Johnson&Johnson and Proclear, Cooper Vision) previously soaked in 100mL contact lens care solutions (Optifree, Alcon; Biotrue, Bausch-Lomb; and Renu, Bausch-Lomb) for 96 hours according to 1994 FDA Premarket Notification 510(k) Guidance Document for Daily Wear Contact Lenses and rinsed with a marine ionic solution (Lacrymer, Yslab, France).
Results: :
Optifree and Menicare Plus induced a loss of cell viability: 26% of living cells according to neutral red assay and 49% of living cells according to alamar blue assay for Optifree, 42% of living cells according to neutral red assay and 76% of living cells according to alamar blue assay for Menicare Plus. Optifree, the most cytotoxic multipurpose solution, was also adsorbed on both Acuvue Advance and Proclear contact lenses and released on corneal cells. This release from Acuvue Advance and Proclear induced a decrease in cell viability of 55% and 36%, respectively. Optifree cytotoxicity was totally abolished when a rinse step with Lacrymer was added to the cleaning procedure.
Conclusions: :
ISO 10993-5 standard could be improved for the evaluation of contact lens care solutions: the cell line, the incubation time and the solutions dilution have to be adapted to the ocular surface field to better discriminate contact lens care solutions. Among the four contact lens care solutions tested, two were highly cytotoxic. This cytotoxicity could be avoided by a rinse step with unpreserved marine ionic solution.
Keywords: contact lens • cornea: epithelium • apoptosis/cell death