Key points are not available for this paper at this time.
Department of Ophthalmic Optics, The University of Manchester Institute of Science and Technology, Manchester, U.K. Received March 25, 1982 * Ph.D. AUTHOR'S ADDRESS: W. N. Charman The Univesity of Manchester Institute of Science and Technology Department of Ophthalmic Optics P.O. Box 88, Sackville Street Manchester M60 1QD, U.K.
Charman et al. (1982) studied this question.