In vitro compatibility study of a new preservative‐free multidose 0.6% bilastine eye drop formulation containing sodium hyaluronate with soft and gas rigid permeable contact lenses

Aims/Purpose: Despite many patients with allergic conjunctivitis are contact lens wearers, research on the physical compatibility of antihistamine eye drops and contact lenses is lacking. The aim of this work was to evaluate the in vitro compatibility of a new preservative‐free bilastine eye drops with the main types of contact lenses. Methods: The physical compatibility of a new preservative‐free bilastine eye drops in comparison with an isotonic saline solution, was evaluated in three types of contact lenses: hydrogel, silicone hydrogel and gas rigid permeable. Physical properties evaluated: diameter of the lens, posterior vertex power, radius of curvature, physical appearance, and spectral transmittance were characterized. For initial characterization, the lenses ( n = 60) were equilibrated in a saline solution at 20–25°C for 24 h. After, 10 lenses of each type were separately immersed in either the saline solution or the bilastine formulation, both at 20–25°C, for 1 h, and then subjected to 30 wash cycles. The physical characterization was carried out after 1, 15 and 30 wash cycles, measurements performed in triplicate. Measurement methods and tolerance limits of the physical properties and general procedure and performance criteria for assessing the physical compatibility of contact lens were conducted in accordance with the guidelines (UNE‐EN ISO 18369‐3:2007; UNE‐EN ISO 18369‐2:2007; UNE‐EN ISO 11981:2013). Results: The incubation of contact lenses with the new preservative‐free bilastine eye drop formulation did not affect any of the physical properties of the lenses and the results were comparable to those exposed to the control saline solution. The physical properties of all the contact lenses tested in both conditions complied with the manufacturer's specifications and tolerance limits stablished. Conclusion: These results indicate that the new preservative‐free bilastine eye drop is physically compatible with soft and rigid gas permeable contact lens.