SLOPE-BASED ECCENTRIC PHOTOREFRACTION - THEORETICAL-ANALYSIS OF DIFFERENT LIGHT-SOURCE CONFIGURATIONS AND EFFECTS OF OCULAR ABERRATIONS

A geometrical-optical technique is used to predict the changes in the slope of the eccentric-photorefraction intensity profiles as a functio n of refractive state. We investigate how the intensity profiles vary with refractive state for different light source configurations and mo nochromatic aberrations in the eye. The best possible light source con figuration extends from zero eccentricity (to increase sensitivity and reduce the dead zone) to a high eccentricity (to increase the working range). An advantage of using the extended light source is that the i ntensity profile of the eccentric-photorefraction reflex is more linea r for extended sources than for point light sources. It is also shown that the change in slope with refractive state is dependent on pupil s ize. Furthermore, when asymmetric aberrations are present, the change in intensity profile slope with refractive state is dependent on the c ircumferential position of the light source, but this dependence can b e resolved by averaging slope values obtained by using two sources pla ced on opposite sides of the pupil. The importance of this study to ex isting eccentric-photorefractor designs is discussed, and recommendati ons for improved eccentric photorefractors are suggested. (C) 1997 Opt ical Society of America.