Off-axis measurements of a plano distance power progressive addition lens

To test that the Humphrey Lens Analyzer can be used validly to measure off-axis powers of progressive addition lenses of low distance power, we made measurements of a plano distance progressive power lens with both a conventional focimeter and the Humphrey Lens Analyzer. The use of the Humphrey Lens Analyzer in two modes, one in which the lens rotated about a point corresponding to the centre-of-rotation of the eye (mode 1) and one in which the lens rotated about its back surface centre of curvature (mode 2), gave off-axis power measurements which were similar to those of conventional measurements. In addition, the Humphrey Lens Analyzer in mode 1 gave prism measurements which were similar to conventional measurements. The Humphrey Lens Analyzer in mode 2 gave prism measurements which were less than those of conventional measurements, but the prism contours were similar and the differences were < 1 delta within 20 mm of the lens centre.