[Computerized videokeratoscopy. Indications for postoperative suture removal].

Twenty-three patients who had a high degree of postoperative astigmatism (3 D) after extracapsular cataract extraction were examined in a prospective study with a computerized videokeratoscope. Sutures were removed within the first 3 months postoperatively, and an examination with the videokeratoscope was performed at the same time. In addition, corneal power was measured with a keratometer for comparison. A comparative map demonstrating the change in corneal shape can be obtained by simple subtraction of the pre- and postoperative keratographs (color-coded topographical maps). Immediately after suture removal the corneal curvature was flattened in the steepest meridian (3 mm and 5 mm zone), resulting in an average net change in cylindrical refraction of -1.3 (+/- 1.7)D. The steepest meridian moved slightly in a counterclockwise direction (-5.79 +/- 29.4 degrees). The topographical analysis of all cases showed that suture removal along the steepest meridian reduced astigmatism by flattening the steepest meridian and steepening the flattest meridian. As the peripheral cornea becomes steeper, the central cornea flattens in a meridian. Morphologically, three different patterns were found. In 52% the reduction in astigmatism was "symmetric", in 21% it was "round", and in 26% it was "irregular". As a result of the study, a topographical model of the cornea will be given, showing the average net change in diopters power at various locations on the surface of the cornea. These results cannot be described by the use of ordinary keratometers.