The use of computerized corneal topography in the assessment of astigmatism
Purpose. The keratometer has been the predominate device used to evaluate astigmatism. The introduction of computerized corneal topography offers an alternate means for measuring astigmatism. Our purpose was to evaluate 2 computerized corneal topography systems, EyeSys and PAR, in the assessment of astigmatism. Methods. Readings obtained from 12 astigmatic patients with otherwise normal eyes (21 eyes) using EyeSys and PAR were compared to data from the Topcon™ Auto-Keratometer, which was chosen as a reference. Eye Sys uses placido disc imaging, whereas PAR utilizes rasterstereography to determine corneal contour. We evaluated these 2 new methods and compared results with standard keratometry. Results. The cylindrical range is Topcon™: 0.12D to -5.37D; EyeSys 0.00D to -4.96D; PAR 0.35D to -4.61D. The standard error for all three instruments is ±0.25D. Both EyeSys and PAR differ from Topcon™ by +2° in the measurements of the principal meridians. Mean deviations from Topcon™ in refractive power at the flattest/steepest axis are 0.02D/0.46D for EyeSys and 0.71D/0.68D for PAR. T-tests confirm that data obtained from the 3 instruments are not statistically different from one another (p>0.05). Conclusions. In assessing astigmatic patients with normal eyes, both the EyeSys and PAR computerized corneal topography systems are consistent with measurements by autokeratometry.
Perez, V; Krashin-Bichler, I; Dunn, M; Schwartz, BA; Lee, C; Shu, DK; Asbell, PA
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