Static cyclotorsion measurements using the Schwind Amaris laser

Abstract

Purpose: To assess the reliability and reproducibility of static cyclotorsion correction (SCC) measurements made using the Schwind Amaris Excimer laser in patients undergoing LASIK or PRK, and compare the outcomes of treating astigmatism with and without SCC.

Methods: Eighty eyes of 40 patients were included in this study. All eyes underwent 2 or 3 sets of five measurements: before and after speculum placement, and after flap-lift (in LASIK cases). We assessed the reproducibility, accuracy, and the percentage of “no catch” measurements. The astigmatism was calculated pre-and 3-months-postoperatively by vector analysis.

Results: The mean age of the patients was 23.67 ・} 4.19 years. Preoperative spherical equivalent and astigmatism were -2.56 ・} 2.86 D and +1.36 ・} 0.98 D, respectively. The mean measurement time was 15.1 seconds per measurement. The percentages of “no catch” were: 63.8%, 14.9%, and 26.9%; pre-speculum, post-speculum, and post flap-lift, respectively. Cyclotorsion of ≥}2° was seen in 41.25% and 66% of the cases before and after the flap-lift, respectively. Significant cyclotorsion (≥}5°) was seen in 12.50% and 18% of the eyes pre and post flap-lift. The mean astigmatism dropped from +1.53 D@1° to +0.34D@3° when SCC was used and from +1.86D@1° to +0.23D@7° when SCC was not used. No statistical difference was noticed between the groups (p>0.05) in the postoperative residual astigmatism. A postoperative astigmatism of ≥ D was seen in 10% and 20% of eyes with and without SCC, respectively (p<0.01).

Conclusion: Although not always feasible, the SCC measurement is a simple and useful tool. Postoperative astigmatism showed less variability when SCC was used.