[Measurement of the radius of corneal curvature with the Maloney surgical keratometer and an on-line keratometer imagery processing system].

A system for measuring the radius of the corneal curvature using the Maloney surgical keratometer (Keratoring), designed for prescribing contact lenses in cases in which it is not possible to measure the radius of the corneal curvature by conventional methods, was tested, and its precision and practicality were evaluated. The subjects were 67 eyes in 34 healthy adults and steel globes for photokeratometer calibration with radii of curvature of 6.73 mm, 7.91 mm and 9.07 mm. The Placido ring projected by the Keratoring was first transmitted to video image processing board via a video unit, and the image was analyzed using a program developed by the authors. Measurements of the globes were possible within a range of error of +/- 0.05 mm, enabling extremely precise analysis. Furthermore, when the average radius of the corneal curvature of human corneas was measured, deviation from the ophthalmometer reading was within 0.2 mm in 87% of cases. When minor meridians were compared, it was found to be possible to measure to within 0.3 mm in 90% of cases. It therefore appears appropriate to apply this method as an index for prescribing contact lenses, especially in cases where conventional methods cannot be performed.