Slippage of Contact Lenses and other Artefacts in Relation to Fading and Regeneration of Supposedly Stable Retinal Images

After-image experiments reveal that scleral-fitting contact lenses slip through several minutes of arc. Experiments in which they have been used to procure “stabilized” retinal images must therefore be reinterpreted. Light-weight, suck-on, limbal-seating cups are much better, but complete stabilization cannot be relied upon. Other possible artefacts in stabilized image work are described and are thought to be responsible for certain features of previous accounts of the appearance of stabilized images. Discounting features caused by artefacts, the image appears to blur, losing detail, and fade, losing contrast, within the first few seconds. Contrast and detail are not regained, but the milky, textureless image that remains fluctuates in appearance for a minute or so. Finally the fluctuations die out and a very blurred, cloudy version of the original scene persists.