Marked accommodation, retinal stretch, monocular space perception and retinal receptor orientation.

In recent years we have come to recognize that retinal receptors are probably aligned with the center of the exit pupil of the eye. It becomes crucial to define those factors influencing and determining photoreceptor alignment. Here, the effect of retinal stretch associated with marked accommodation has been considered. Assuming that a sense of direction is associated with a given retinal locus, we have used a classical monocular bisection test technique in order to see if marked accommodation altered bisection settings. Substantial changes in bisection settings were found when testing in the region of the posterior pole. These could be localized most probably in the retina and choroid. In separate studies, the effect of anterior retinal stretch upon cone receptor orientation in the region of the fovea was evaluated. Marked accommodation caused a transient nasal displacement of the peak of the Stiles-Crawford directional sensitivity function. These studies suggest that the posterior pole of the eye is routinely subject to stresses and strains. This point is of clinical significance. Our studies suggest that the presence of the blind spot influences the magnitude of change of measured parameters. We have only begun the important task of evaluating the nature of recovery processes following marked accommodation. Lastly, in order to obtain the necessary responses, we have had to train our young observers to voluntarily utilize nearly their entire accommodative capability.