The measurement of soft lens radii by proximity gauging

Thirty hydrogel lenses with a water content of 60% were examined in the Kelvin Soft Lens Measurement Gauge in order to assess their back central optic radii (BCOR). The accuracy, repeatability and limitations of the equipment were considered. The proximity gauging principle avoids central touch of the lens by a probe at the time of measurement. This factor almost certainly contributed to the good measurement consistency obtained (a modal SD of 0.02 mm for four radius measurements).