The production and fading of entoptic images

A new apparatus, suitable for obtaining reliable reports of entoptic images, was developed. Basically, this apparatus moved a small light across the S’s eyelid (transcleral illumination). While the light was moving, Ss reported the appearance of the three entoptic phenomena of interest-retinal blood vessels, foveal images, and background illumination. After initial training with this apparatus, 12 Ss were tested for the differential disappearance (fading) of the entoptic images after the light source stopped moving but continued its transcleral illumination of the retina. Results indicated that although the background image did fade to a dark field, this background fade time ( \(\bar X\) = 1.3 sec) is faster than that reported for externally stabilized images, which may take 2 to 4 sec to fade, and was significantly slower than the very rapid fade times for blood vessels and foveal images. Furthermore, there was no reappearance of these entoptic images.