The Stiles-Crawford effect of the first kind (SCE I): studies of SCE I in an aniridic observer

The Stiles-Crawford effect of the first kind (SCE I), discovered in 1933, represented a major breakthrough in our understanding of retinal physiology and the modern beginning of the science of photoreceptor optics. The current status of knowledge in this area is briefly reviewed. A study is presented of a white adult female observer with aniridia, clear media, only traces of nystagmus, rather good visual acuity, and good fixation. It is shown that this individual exhibits approximate alignment of her photoreceptors with the center of the retinal sphere, clear evidence of side lobes on functions, and surprisingly steep SCE I functions. The implications of these findings are considered.