Refractive Index Measurement System for Contact Lens in a Natural Hydrated State

A collaboration between Lumetrics and Johnson & Johnson

Accurate refractive index of the contact lenses is one of the most important parameters needed to properly evaluate the lens performance. Measurements of the refractive power and other optical properties of the lenses are typically conducted in solution, and converted to in-air performance. Such an approach is very sensitive to errors in the refractive indices of both the lens and the solution.

We have conducted measurements of the group refractive index (GRI) of hydrogel contact lenses at different wavelengths, from 530 to 670 nm, using time-domain low-coherence interferometer (LCI), based on the super-continuum light source (SCLS). We show that the proposed measurement equipment and technique will allow material phase RI characterization at visible wavelengths with high accuracy of 0.003 or better.