Photoreceptor orientation. A graded disturbance bordering a region of choroidal atrophy

Retinal photoreceptor orientation was found to be disturbed in the region bordering an area of choroidal atrophy in the eye of a human observer. This disturbance was inferred from the locations of the peaks of psychophysical Stiles-Crawford functions. These peak locations progressively shifted from a normal location near the center of the pupil to well beyond the nasal pupillary margin as the retinal test location approached the visible lesion. We conclude that this disturbance of photoreceptor orientation reflects the operation of tractional forces that interfere with the reorientation of the receptors toward the pupil in a sizable area of the retina surrounding the traction-inducing lesion.