The three-point Vernier alignment (or acuity) test was conducted on children from 5 to 9 years old. There is a significant difference between the 5-9 year old subjects and those in age groups 10 to 19 and 20 to 29 years in Vernier performance. These data were also compared with previously published data from older subjects (up to age 70). We conclude that Vernier function has not fully matured within the age range of 5 to 9 years; this finding is consistent with previous results reported in the literature.

No abstract

Probable transient changes in photoreceptor alignments, inferred from the measurements of the Stiles-Crawford effect of the first kind (SCE - I), were demonstrated in myopic eyes with elongated axial length (regardless of the magnitude of refractive error) at three retinal locations; the fovea (point of fixation), and 22 degrees and 27 degrees in the nasal retina. The changes were much bigger at 22 degrees and 27 degrees in the nasal retina (which are located beyond the optic nerve head) than at the fovea. These transient effects were revealed by repeatedly testing the same retinal locations over a period of time. Time intervals between the subsequent/repeated measurements ranged from less than an hour to several months. In some locations, the changes were recorded in less than an hour. Collectively, these were very meaningful changes. Generally bigger effects were recorded in the horizontal SCE - I than in the vertical SCE - I.

Properties of presumed mechanisms controlling photoreceptor alignments are partially defined. A phototropic mechanism normally dominates alignment, but do modest changes in orientations occur with dark patching? Here, new photopic Stiles-Crawford (SCE-I) determinations were made before patching (pre-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 temporal retina of both eyes. Ten eyes of adult subjects were tested. SCE-I peak positions and Stile's parameter 'rho' were assessed. Dark-patching effects were small. Observations revealed meaningful corrective alignment overshoots with recovery in the light. Results suggest (1) the presence of multiple weak mechanisms affecting receptor alignments in the dark; (2) the phototropic mechanism to be dominant in the light; (3) the need for multiple test loci to be sampled in such studies, and (4) small changes in the SCE-I in the pupil plane can reflect meaningful events occurring at the retina.