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Proceedings Paper

Automatic diagnostic system for measuring ocular refractive errors
Author(s): Liliane Ventura; Caio Chiaradia; Sidney Julio Faria de Sousa; Jarbas Caiado de Castro
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Paper Abstract

Ocular refractive errors (myopia, hyperopia and astigmatism) are automatic and objectively determined by projecting a light target onto the retina using an infra-red (850 nm) diode laser. The light vergence which emerges from the eye (light scattered from the retina) is evaluated in order to determine the corresponding ametropia. The system basically consists of projecting a target (ring) onto the retina and analyzing the scattered light with a CCD camera. The light scattered by the eye is divided into six portions (3 meridians) by using a mask and a set of six prisms. The distance between the two images provided by each of the meridians, leads to the refractive error of the referred meridian. Hence, it is possible to determine the refractive error at three different meridians, which gives the exact solution for the eye's refractive error (spherical and cylindrical components and the axis of the astigmatism). The computational basis used for the image analysis is a heuristic search, which provides satisfactory calculation times for our purposes. The peculiar shape of the target, a ring, provides a wider range of measurement and also saves parts of the retina from unnecessary laser irradiation. Measurements were done in artificial and in vivo eyes (using cicloplegics) and the results were in good agreement with the retinoscopic measurements.

Paper Details

Date Published: 17 May 1996
PDF: 9 pages
Proc. SPIE 2673, Ophthalmic Technologies VI, (17 May 1996); doi: 10.1117/12.240071
Show Author Affiliations
Liliane Ventura, Univ. de Sao Paulo (Brazil)
Caio Chiaradia, Univ. de Sao Paulo (Brazil)
Sidney Julio Faria de Sousa, Univ. de Sao Paulo (Brazil)
Jarbas Caiado de Castro, Univ. de Sao Paulo (Brazil)

Published in SPIE Proceedings Vol. 2673:
Ophthalmic Technologies VI
Jean-Marie A. Parel; Karen Margaret Joos; Pascal O. Rol, Editor(s)

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