Sequential Ablation Approach to the Correction of Mixed Astigmatism

Abstract

PURPOSE: To evaluate the safety, efficacy, and stability of LASIK, using positive cylinder and negative sphere nomograms in sequence (sequential ablation) to correct mixed astigmatism. METHODS: This prospective study included 40 eyes of 20 patients with mixed astigmatism. Patients underwent bilateral sequential ablation LASIK using the Technolas 217 excimer laser (Bausch & Lomb Surgical, Rochester, NY). The main outcome measures, uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), were evaluated 3 and 12 months after surgery. RESULTS: Preoperative astigmatism ranged from + 1.75 to +6.00 diopters (D) and negative sphere from -0.50 to -3.00 D. The postoperative refraction at 3 months remained unchanged at 1 year postoperative in all patients. A total of 32 (80%) eyes showed no significant residual astigmatism (<0.50 D); the remaining 8 (20%) eyes had 0.50 to 1.00 D of residual astigmatism. Residual negative sphere was present in 2 eyes of 2 patients with a planned monovision target. In the remaining 38 (95%) eyes, no significant residual negative sphere was present. Sixteen (40%) eyes had one line of improvement in BSCVA. No eye lost lines of visual acuity. The efficacy index shows that uncorrected vision after surgery is equal or better than corrected vision before surgery. Less corneal tissue is removed and fewer laser spots are required compared to other techniques for the correction of mixed astigmatism. CONCLUSIONS: The sequential ablation approach to the correction of mixed astigmatism was efficacious, safe, and stable 1 year after surgery. [J Refract Surg. 2006;22:787-794.]

Treatment of mixed astigmatism: early clinical outcomes withWaveLight and Technolas excimer lasers

“…All eyes had a mean spherical equivalent refraction within ±0.50 D of the intended correction and the residual astigmatism was ≤0.50 D in all eyes treated with the WaveLight Allegretto Wave 400 Hz in the study by Stonecipher et al (1). Pinelli et al (2) reported that 80% of patients (n = 32) treated with the Technolas 217 excimer laser had no residual astigmatism (≤0.50 D) and the remaining 20% (n = 8) had residual astigmatism between 0.50 D and 1.00 D. We found that at postoperative month 3, one eye in the WaveLight group and 3 eyes in the Technolas group had no residual astigmatism (P = 0.213). Spherical equivalent values were -0.38 ± 0.73 D in the WaveLight group and -0.33 ± 0.20 D in the Technolas group (P = 0.562).…”

“…Different approaches have been reported: negative-cylinder nomogram, positivecylinder nomogram, cross-cylinder technique, bitoric ablation, and sequential ablation. The common goal in the treatment of mixed astigmatism is to remove the minimum amount of tissue while achieving good visual results (1,2).…”

“…At postoperative month 3, the mean efficacy was ≥1.00 for both the WaveLight and the Technolas groups. Pinelli et al (2) reported that the efficacy was ≥1.00 in all eyes with the Technolas 217 excimer laser.…”

“…Stonecipher et al (1) reported that at 3 months postoperatively, no eyes lost any lines of CDVA and 3 eyes (12%) gained 1 line with the WaveLight Allegretto Wave 400 Hz excimer laser. Pinelli et al (2) reported that there was no loss of lines of CDVA and 16 (40%) eyes gained 1 line in CDVA at postoperative 1 year with the Technolas 217 excimer laser.…”

“…In the sequential ablation technique, the positive cylinder is treated first and full astigmatism is corrected. A purely myopic eye is obtained and then the negative sphere is treated (2). Different laser systems use these techniques aiming at less tissue ablation with better postoperative visual and refractive results.…”