[The annular scotoma and jack-in-the-box phenomenon in aphakia corrected with eyeglasses. Experimental approach]

An experimental study of "annular scotoma" was conducted. Variations in prismatic effects at the boundary of the lens with respect to incidence were evaluated with the aid of a laser beam. The use of an arc-perimeter and an artificial aphakic eye allowed reconstruction of light beam paths from the outside to the inside of the eye. The results obtained enabled a more rigorous analysis of this optical phenomenon. A straightforward formula obtained from the experiment (tan theta = b/a) provided better understanding of the variations generated by certain parameters. This same formula can be applied to the mechanism of the "Jack-in-the-box" phenomenon.