3114 Optical zone centration of excimer laser photo-refractive keratectomy for myopia relative to the pupil with and without the use of an active eye tracking system

THE EXCENTRIC ASTIGMATISM PRK, A PHOTOREFRACTIVE METHOD TO CORRECT CORNEAL ASTIGMATISM USING TEE 193-NM EXCIMERLASER HUETZ,W.W., EOFFMANN,P.C., ECKHARDTJ3.B. Pumore: The Excentric Astigmatism PRK is a method to correct comeal astigmatism with two peripheral ablations which are performed outside an untreated central zone. Method% Two peripheral ablations of 3.4 mm diameter are performed outside an untreated central zoae 3.0 mm in size in the flatter meridian of the cornea following the usual algorithm of the myopia PRK The amount of the correcting minus cylinder determines the height of the excentric ablations. A total of 17 patients were operated on from October 1993 to November 1994 using this method. Rerult~ In the first group of 5 patients, the astigmatism was reduced by an average of 3.5 dpt (1.75 dpt to 5.0 dpt) to a residual astigmatism of 0.48 dpt, i.e. by 86%. In the second group of 12 patients, a correction of the myopia was carried out with a cetttral6.0 mm PRK at the same time as the correction of astigmatism. In this group, the astigmatism could be reduced from an average of 2.92 dpt (1.25 dpt to 5.0 dpt) to a remaining astigmatism of 0.36 dpt, i.e. by 88%. In the patients with followup observation for eight to 13 months, regression could not be observed in the specified period. Celrclurioar: The Excentric Astigmatism PRK creates a new external radius in the flatter meridian of the cornea. The advantage of this method is, that there is no risk of corned haze in the optical zone