Transverse keratotomy for correction of low astigmatism: evaluation of a simplified nomogram

ABSTRACT

To evaluate a simplified nomogram for the correction of low amounts of astigmatism by transverse keratotomy. Methods Transverse keratotomy for correction of astigmatism was performed on 109 eyes of 71 myopic astigmatic patients [age range, 21 to 45 years; mean 33 years] in whom refractive astigmatism ranged from 1.0 to 3.0 diopters [D] [mean, 1.68D]. The number of transverse incisions and the size of the optical zone were selected on the basis of a simple nomogram modified from the nomograms developed by Thornton and Casebeer. All procedures were performed by the same surgeon and were combined with radial keratotomy for correction of myopia. The results were evaluated using simple analysis and vector analysis. The follow up period ranged from 6 months to 2 years [mean, 13.2 months]. At the final postoperative visit, the mean residual astigmatism was 0.54D [SD = 0.48; range, 0 to 2.25D]. The width of the 90% confidence interval for the residual astigmatism was 1.25D [range, 0 to 1.25D]. The mean decrease in astigmatism was 1.14D. Surgically induced astigmatism in the desired axis within 0.50D of preoperative astigmatism was achieved in 81 eyes [74.3%]. The axis of the surgically induced astigmatism deviated by less than 100 from the desired axis in 71.6% of eyes. Astigmatism can be effectively corrected by transverse keratotomy. The nomogram evaluated here is simple and reliable for correction of astigmatism up to 3.0D