An apparent failure of the photoreceptor alignment mechanism in a human observer

Using the psychophysical Stiles-Crawford function, the orientation of the retinal photoreceptors was shown to be directed toward a region near the center of the eye rather than the pupil in one eye of a human observer. Since an observable pathologic condition was not present, this eye was concluded to represent the first demonstrated instance of a primary global disturbance of the normal receptor alignment mechanism. The examination of this unique observer permits the visual importance of normal receptor orientation to be assessed and allows potential photoreceptor alignment mechanisms to be evaluated.