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Abstract: Cantor rings are rotational symmetric pupils that are generated from a Cantor set of a given level of growth. These pupils have certain fractal properties. For example, it is known that when illuminated by a general spherical wavefront they provide self-similar patterns at transverse planes in the Fraunhofer region. In this paper, we study the response of Cantor rings when illuminated by a Bessel light beam conforming what we call fractal axicons. It is shown that, with this kind of illumination a close replica of the radial profile of the pupil is obtained along the optical axis, i.e., we show that the axial behaviour of these pupils has self-similarity properties that can be correlated to those of the diffracting aperture. The influence of several construction parameters is numerically investigated. [Copyright &y& Elsevier]

Children in mainstream schools compared text on white paper with identical text covered in turn by each of ten differently-coloured plastic overlays. More than 50% reported improved perception with one or more colours, and were given the best colour to use. About half used the overlays for more than three months and their reading speed increased when the overlays were used. In Study I children were examined twice using different methods and examiners. 47% chose the same colour on both occasions, and showed the greatest improvement in reading fluency, reliable at retest. In Study II children were issued with a random colour, and the greatest improvements in reading speed occurred when the random colour was the same as that previously chosen. Phonological reading strategies were not related to visual symptoms, or the benefit from overlays. Across individuals, reading speed varied by a factor of more than three, for good and poor readers. Study III provided estimates of the prevalence of improvements based on a sample of 426 children from 12 schools: 5% of children read more than 25% faster with a coloured overlay. [ABSTRACT FROM AUTHOR]