Stiles-Crawford effect of the first kind: assessment of photoreceptor alignments following dark patching

Properties of presumed mechanisms controlling photoreceptor alignments are partially defined. A phototropic mechanism normally dominates alignment, bu t do modest changes in orientations occur with dark patching? Here, new pho topic Stiles-Craw ford (SCE-I) determinations were made before patching (pr e-patch), just after 8-days of dark-patching (post-patch), and 3 days after patch removal (recovery test). We tested at 0, 11 and 22 degrees in the te mporal retina of both eyes. Ten eyes of adult subjects were tested. SCE-I p eak positions and Stile's parameter 'rho' were assessed. Dark-patching effe cts were small. Observations revealed meaningful corrective alignment overs hoots with recovery in the light. Results suggest (1) the presence of multi ple weak mechanisms affecting receptor alignments in the dark; (2) the phot otropic mechanism to be dominant in the light; (3) the need for multiple te st loci to be sampled in such studies, and (4) small changes in the SCE-I i n the pupil plane can reflect meaningful events occurring at the retina. (C ) 2000 Elsevier Science Ltd. All rights reserved.