Intraoperative keratometry with the oval comparator (astigmometer) *

SUMMARY The Astigmometer is a simple accessory which is attached to a surgical microscope. It allows precise suturing of the cataract wound and reduced the amount of postoperative astigmatism at six weeks. This allowed rapid visual rehabilitation and more active patients. It obviated the removal of sutures in the postoperative period in most patients (90%). However, stable results after one year were obtained with selective suture cutting without the use of intraoperative keratometry. This was almost as good as in the astigmometer group, but the percentage of astigmatism less than 1 dioptre was reduced and that greater than 2 dioptres was increased. With the advent of the intraocular lens and extended wearing of contact lenses rapid return of good vision without spectacles is possible if minimal astigmatism has been induced by the surgeon. Many authors have reported attempts to minimise postoperative astigmatism by using modified surgical techniques or the use of measuring devices to determine the amount of astigmatism induced on the operating table by the sutures.'-3 The most detailed reports are those describing the use of the Terry keratometer.' However, the cost, complexity, and difficulty in using this system has prevented more universal acceptance. An attempt was made to develop a new type of instrument to determine intraoperative astigmatism and set up the wound so that the natural wound slippage would return the cornea to a near perfect shape. Theory and description of astigmometer The light source is a circular arrangement of high-intensity light-emitting diodes attached to the operat-ing microscope body. A self-illuminating ring in the focal plane of one eyepiece is rotated about its axis by means of a dial with a sterilisable cover. The oval produced is matched to that of the reflected light ring produced by the anterior corneal curvature. B