A geometrical-optical technique is used to predict the changes in the slope of the eccentric-photorefraction intensity profiles as a function of refractive state. We investigate how the intensity profiles vary with refractive state for different light source configurations and monochromatic aberrations in the eye. The best possible light source configuration 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 intensity profile of the eccentric-photorefraction reflex is more linear for extended sources than for point light sources. It is also shown that the change in slope with refractive state is dependent on pupil size. Furthermore, when asymmetric aberrations are present, the change in intensity profile slope with refractive state is dependent on the circumferential position of the light source, but this dependence can be resolved by averaging slope values obtained by using two sources placed on opposite sides of the pupil. The importance of this study to existing eccentric-photorefractor designs is discussed, and recommendations for improved eccentric photorefractors are suggested.
© 1997 Optical Society of America
Original Manuscript: November 18, 1996
Revised Manuscript: May 13, 1997
Manuscript Accepted: May 13, 1997
Published: October 1, 1997
Austin Roorda, Melanie C. W. Campbell, and William R. Bobier, "Slope-based eccentric photorefraction: theoretical analysis of different light source configurations and effects of ocular aberrations," J. Opt. Soc. Am. A 14, 2547-2556 (1997)