The subjective quality (SQF) of Bausch and Lomb SoflensTM

The visual acutiy of a person is examined in terms of his response to a unique target. This target is a sequence of black bars on a white background, where the spacing of the bars and their width is governed by a log periodic function. The generation of these targets is performed by a PDP-8 computer connected to an X-Y plotter. There are six sets of bars which vary in contrast and frequency. In a clinical situation, an observer notates the position where he can no longer resolve the bar pattern. A recroding of these positions produces a Subjective Quality Function (SQF) curve for the individual. On fitting with soft contact lenses, a new SQF curve is generated. A comparison of the SQF for soft lenses with that for spectacle corrections is given.