v gauge

v gauge 

A device used to measure the total diameter of a rigid contact lens. It consists of a channel cut into a long rectangle of plastic or metal. The channel increases in width from 6.0 to 12.50 mm and a scale is printed beside it. The lens is placed with its concave surface down at the widest end of the channel and that end of the gauge is raised so that the lens slides down the channel until it stops. The diameter is then read from the scale where the lens touches the side of the channel. Syn. v-channel gauge.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann