Fast Photoelectric Estimation of Oxygen Transmissibility of Silicone Hydrogel Contact Lens

Nominal oxygen transmissibility (Dk/t) values on commercial product packages are usually of the lens material instead of the actual values of contact lenses (CLs) derived based on their power. To evaluate the Dk/t values of CLs of different powers, we developed a rapid photoelectric method. In the experiment, a photodiode was employed to detect variations in the light intensity passing through silicone hydrogel (Si-Hy) CLs over a period. Light intensity variations can indicate the water content (WC) and power of Si-Hy CLs and help calculate the Dk/t of Si-Hy CLs of different powers. Experimental results indicated that the WC and specific power of Si-Hy CLs were determined by the initial attenuation voltage, which ranged from 0.73 to 1.15 V for the lenses tested herein, whereas the WC varied from 38% to 56%. The Dk/t of Si-Hy CLs at -3.00 D was determined from the voltage variation over 3 min after reaching the peak voltage and the Dk/t corresponding to a specific power could be evaluated from the ratio of initial attenuation voltage of a lens having a specific power to that having -3.00 D. The results of this study can serve as reference information for quality control in factories.