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Proceedings Paper

Digital photorefraction
Author(s): Manuel F. M. Costa; Jorge M. Jorge
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Paper Abstract

The early evaluation of the visual status of human infants is of a critical importance. It is of utmost importance to the development of the child's visual system that she perceives clear, focused, retinal images. Furthermore if the refractive problems are not corrected in due time amblyopia may occur. Photorefraction is a non-invasive clinical tool rather convenient for application to this kind of population. A qualitative or semi-quantitative information about refractive errors, accommodation, strabismus, amblyogenic factors and some pathologies (cataracts) can the easily obtained. The photorefraction experimental setup we established using new technological breakthroughs on the fields of imaging devices, image processing and fiber optics, allows the implementation of both the isotropic and eccentric photorefraction approaches. Essentially both methods consist on delivering a light beam into the eyes. It is refracted by the ocular media, strikes the retina, focusing or not, reflects off and is collected by a camera. The system is formed by one CCD color camera and a light source. A beam splitter in front of the camera's objective allows coaxial illumination and observation. An optomechanical system also allows eccentric illumination. The light source is a flash type one and is synchronized with the camera's image acquisition. The camera's image is digitized displayed in real time. Image processing routines are applied for image's enhancement and feature extraction.

Paper Details

Date Published: 1 January 1998
PDF: 9 pages
Proc. SPIE 3199, Biomedical Systems and Technologies II, (1 January 1998); doi: 10.1117/12.301102
Show Author Affiliations
Manuel F. M. Costa, Univ. do Minho (Portugal)
Jorge M. Jorge, Univ. do Minho (Portugal)


Published in SPIE Proceedings Vol. 3199:
Biomedical Systems and Technologies II
Francesco Baldini; Nathan I. Croitoru; Mark Russell Dickinson; Martin Frenz; Mitsunobu Miyagi; Riccardo Pratesi; Stefan Seeger, Editor(s)

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