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 rot ated 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 cent re of curvature (mode 2), gave off-axis power measurements which were similar to those of conventional measurements. In addition, the Humphr ey Lens Analyzer in mode 1 gave prism measurements which were similar to conventional measurements. The Humphrey Lens Analyzer in mode 2 gav e prism measurements which were less than those of conventional measur ements, but the prism contours were similar and the differences were < 1 DELTA within 20 mm of the lens centre.