SUMMARY
Purpose:
We have developed the first Brazilian Videokeratograph (or less accurately, Corneal Topographer).
Methods:
Placido discs painted on a conic pattern are reflected by the cornea. The images are magnified and focused on a CCD behind the cone. The CCD’s signal is sent to a frame grabber mounted on a compatible IBM PC. By means of digital image processing algorithms, border distances of the Placido discs are extracted from the digitized images. These values are put into an algorithm with mathematical models of the corneal curvature.
Results:
As in other topographers a color coded diopter plane map is plotted on the computer screen. For a set of 9 spheres of radius: 5.50, 5.75, 6.00, 6.25, 6.75, 7.00, 7.25, 7.50, 7.75 mm an error of 0.1 diopter for refractive power and 0.02 mm for curvature, was obtained. 5,760 points were analyzed for each sphere. Exams of 20 corneas were compared and an error of 0.2 diopters was obtained relative to an Eyesys topographer.
Conclusions:
We may affirm that with our instrument results very similar to those of the topographer used for comparison are obtained.
Keywords:
Corneal topography; Keratometry; Placido Discs