Comparison of cross cylinder ablation using the optimized ablation transition zone and the torsion error detector for...

To compare the safety and efficacy of laser in situ keratomileusis (LASIK) in correcting high myopic astigmatism using two different ablation profiles using the Nidek EC-5000 CX II laser).

Fifteen patients (25 eyes) had LASIK for compound myopic astigmatism, using the Optimized Ablation Transition Zone (OATz) ablation profile and activated torsion error detection (TED). Results were compared with those obtained with a cross cylinder ablation profile for myopic astigmatism.

For eyes treated with TED, on postoperative day 7, 76% had visual acuity equal to or better than baseline best spectacle-corrected visual acuity (BSCVA) and 56% of eyes had overcorrected astigmatism. On postoperative day 20, none of the eyes had residual astigmatism more than 1.00 D and 72% eyes were within +/-0.50 D cylinder; 92% of eyes had residual astigmatism within 30 degrees of the preoperative axis and 12% remained astigmatically overcorrected at 20 days. Eighty-eight percent of eyes were either fully corrected or had mild myopic astigmatism. Comparison of results with cross cylinder ablation showed that 24% had overcorrection and 60% of patients with high astigmatism were overcorrected up to 1.75 D and developed hyperopic astigmatism in the opposite axis. Results with the cross cylinder ablation profile were good up to 2.00 D of myopic astigmatism.

Correction of astigmatism using the OATz profile and TED with the Nidek EC-5000 CX II laser produced good results in high as well as pure astigmatism treatments, compared to the cross cylinder ablation profile. Ablation depth was greater in OATz with TED-based corrections. Overcorrections were less with OATz with TED, and residual astigmatism was at the same baseline axis, thereby increasing patient satisfaction.