Measurement of the refractive indices of hydrogel materials by interferometry.

The purpose of this study was to measure the refractive indices of hydrophilic hydrogel materials of different equilibrium water content. The need to measure the refractive indices precisely has been an important factor in the design of soft hydrophilic lenses. The inaccuracy of measuring the refractive index of hydrogel materials using an Abbé refractometer led to the use of a Linnik micro-interferometer. The experimental results showed a close agreement to the theoretical data.