Effect of wavelength and the Stiles–Crawford effect on the Nonius horopter

Abstract

This study examines the effect of wavelength on the Nonius horopter. We have investigated whether the observed change in directionality is due to chromostereopsis and the Stiles–Crawford effect (SCE). The Nonius horopter was measured foveally in five subjects as a function of four different wavelengths. Illumination and pupil condition were varied. Chromostereopsis was also recorded. The result for the different luminance conditions reveals that SCE modifies the curves under photopic conditions, and the direction of the horopter corresponds to the direction of chromostereopsis. We conclude that the changes in the horopter curves are due to both optical and neural factors.

Keywords:

• Nonius horopter
• fovea, chromostereopsis
• Stiles–Crawford effect
• chromatic aberration
• wavelength

Acknowledgements

We thank Drs Jerry Christensen and Sonia Bahar for their valuable comments and help. We also thank the subjects who participated in this study.