Optical quality comparison among different Boston contact lens materials

BackgroundThe aim was to assess the optical quality of four Boston contact lens materials with an optical device based on Schlieren interferometry. MethodsThe NIMO TR1504 (Lambda-X, Nivelles, Belgium) was used to measure higher-order aberrations and their corresponding root mean square values of four different rigid gas permeable contact lenses made from four different Boston materials: EO, ES, XO and XO2. For each lens, 30 measurements were performed with two optical apertures: 3.0 mm and 6.0 mm. The modulation transfer function, point spread function, Strehl ratio and a simulation of the image provided by the lens were computed from the Zernike coefficients measured up to the fourth order. ResultsThe root mean square error of higher-order aberrations varied significantly with material type for both optical apertures (p < 0.01). The largest difference was obtained between the Boston EO and the Boston ES materials (for a 6.0 mm aperture), the mean difference being (8.3 0.2) x 10(-2) mu m. The modulation transfer functions, point spread functions and Strehl ratio values were similar among all Boston materials at the smaller optical aperture; however, differences between each material were more apparent for the 6.0 mm aperture, with the Boston ES material exhibiting the best optical quality. ConclusionsIn terms of all metrics analysed, all Boston materials examined showed comparable optical quality for a 3.0 mm aperture but the Boston ES material displayed the best optical quality for a 6.0 mm optical aperture.