Transverse incisions for mixed and myopic idiopathic astigmatism

Purpose: To determine the efficacy and safety of the Casebeer transverse nomogram for correcting idiopathic astigmatism using transverse incisions (T-incisions) with variable optical zones. Setting: Rancho Bernardo Eye Center, San Diego, California. Methods: This retrospective study comprised 173 eyes of 100 consecutive patients who had T-incisions according to the Casebeer transverse nomogram to correct mixed or myopic astigmatism. Preoperative cylinder ranged from 0.75 to 6.00 diopters (D). The nomogram was modified for eyes with preoperative cylinder from 1.75 to 6.00 D. Principal outcome measures were net residual astigmatism for all eyes and uncorrected visual acuity in eyes with the highest preoperative cylinder (3.25 to 6.00 D). Results: A comparison of preoperative astigmatism (mean 3.07 D +/- 1.53 [SD]) and net residual astigmatism showed significant reduction in all diopter categories. Enhancements were done in 16.2% of eyes, mostly those with high preoperative cylinder. Patient age did not seem to affect results. No patient, including those with smaller optical zones, lost two or more Snellen lines of best corrected visual acuity. Conclusion: Use of the Casebeer transverse nomogram with T-incisions and variable optical zones effectively and safely reduced most idiopathic astigmatism between 0.75 and 5.50 D. Modifications to the nomogram yielded similar results in eyes with a higher preoperative cylinder.