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Proceedings Paper

Preliminary results of a computerized Placido disk surgical corneal topographer
Author(s): Luis A.V. Carvalho; S. A. Tonissi; Jarbas C. Castro
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Paper Abstract

We have developed a novel instrument for computerized corneal topography during surgery. The instrument measures a region of approximately 7 mm in diameter, providing the surgeon with precise values of power and astigmatism. The system is based on a Placido Disc projecting system, which is attached to the objective lens of the surgical microscope. The Placido Disc pattern is reflected by a 50% beam splitter attached to the body of the microscope. At the beam splitter we installed our home-made adaptor and a CCD monochromatic high resolution camera. A high quality frame grabber is installed on a PC and images are digitized at a 480x640 resolution. Algorithms based on image processing techniques were implemented for edge detection of pattern. Calibrating curves based on 4 spherical surfaces were generated and approximately 3600 points were calculated for each exam. Preliminary measurements on 10 healthy corneas were compared with the measurements made on an EyeSys Corneal Topographer. Mean deviation was 0.05 for radius of curvature, 0.24 D for power and 5 degrees for cylinder. This system, with some improvements, may be successfully used to diminish high post surgical astigmatisms in surgeries such as cataract and corneal transplant. This system could also be used to gather preoperative data in corneal topography assisted LASIK.

Paper Details

Date Published: 18 June 1999
PDF: 10 pages
Proc. SPIE 3591, Ophthalmic Technologies IX, (18 June 1999); doi: 10.1117/12.350608
Show Author Affiliations
Luis A.V. Carvalho, Univ. of California/Berkeley and Univ. de Sao Paulo (Brazil)
S. A. Tonissi, Univ. de Sao Paulo (Brazil)
Jarbas C. Castro, Univ. de Sao Paulo (Brazil)


Published in SPIE Proceedings Vol. 3591:
Ophthalmic Technologies IX
Bruce E. Stuck; Pascal O. Rol; Michael Belkin; Karen Margaret Joos; Fabrice Manns; Bruce E. Stuck; Michael Belkin, Editor(s)

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