Optical ray tracing-guided myopic laser in situ keratomileusis: 1-year clinical outcomes

Abstract

Purpose: To compare the safety, efficacy, and predictability of laser in situ keratomileusis treatments at 1 year postprocedure using a novel geometric ray tracing algorithm with outcomes of treatments using wavefront-optimized, wavefront-guided, and topography-guided ablation profiles of an excimer laser (WaveLight GmbH, Erlangen, Germany; Alcon Laboratories, Fort Worth, TX, USA).

Setting: Wellington Eye Clinic, Dublin, Ireland.

Design: Retrospective comparative case series.

Methods: Eyes having a preoperative myopic spherical equivalent refractive error >4.00 D and/or astigmatism between 2.00-6.00 D resulting in a spherical equivalent power greater than -4.00 D received laser in situ keratomileusis treatments using a ray tracing algorithm. Refractive outcomes were analyzed postoperatively at 6 and 12 months and were compared to outcomes of wavefront-optimized, wavefront-guided, and topography-guided treatments in eyes with the same pretreatment refractive range.

Results: Forty-seven eyes of 26 patients were treated using the ray tracing algorithm. At 12 months postprocedure, uncorrected visual acuity was better than the preoperative best-corrected visual acuity in this group. The percentage of eyes achieving an uncorrected visual acuity or best-corrected visual acuity ≥20/20 significantly exceeded the rates achieved in the wavefront-optimized and topography-guided groups. A greater percentage of eyes achieved an uncorrected visual acuity ≥20/20 and ≥20/16 in the wavefront-guided group, but no eyes in the wavefront-guided group had an uncorrected visual acuity ≥20/12.5 in comparison to 9.5% of eyes in the ray tracing group.

Conclusion: This study provides further evidence of the safety, efficacy, and predictability of laser in situ keratomileusis outcomes using an optical ray tracing algorithm to treat moderate to high myopic astigmatism and shows that good results are sustained through 1 year.

Keywords: Gullstrand eye model; LASIK; ablation profiles; optical ray tracing; topography-guided; wavefront-guided; wavefront-optimized.

Figure 1

Graph of efficacy data comparing the preoperative best-corrected visual acuity results to the 6-month postoperative uncorrected visual acuity results. Notes: At 6 months posttreatment, postoperative uncorrected visual acuity was very comparable to the preoperative best-corrected visual acuity in the ray tracing group. The red bars show preoperative best-corrected visual acuity and the blue bars show postoperative uncorrected visual acuity; the actual number of patients is represented by the percentages at the top of the bars.

Figure 2

Graph showing the magnitude of postoperative refractive astigmatism in the ray tracing group at 6 months posttreatment. Notes: At 6 months postprocedure, 91% of eyes had ≤0.50 D of cylinder. The red bars show preoperative astigmatism and the blue bars show postoperative astigmatism; the actual number of patients is represented by the percentages at the top of the bars. Abbreviation: D, diopter.

Figure 3

Graph of efficacy data for a subset of eyes in the ray tracing group having preoperative spherical equivalent refractive error in the lower range (−4.00 to −5.00 D) of eyes enrolled in the study. Notes: This graph compares the preoperative best-corrected visual acuity results to the 6-month postoperative uncorrected visual acuity results. At 6 months posttreatment, postoperative uncorrected visual acuity was superior to the preoperative best-corrected visual acuity in this subset of eyes in the ray tracing group. The red bars show preoperative best-corrected visual acuity and the blue bars show postoperative uncorrected visual acuity; the actual number of patients is represented by the percentages at the top of the bars. Abbreviation: D, diopter.

Figure 4

Graph of efficacy data comparing the preoperative best-corrected visual acuity results to the 12-month postoperative uncorrected visual acuity results in the ray tracing group. Notes: At 12 months posttreatment, postoperative uncorrected visual acuity was superior to the preoperative best-corrected visual acuity in the ray tracing group. The red bars show preoperative best-corrected visual acuity and the blue bars show postoperative uncorrected visual acuity; the actual number of patients is represented by the percentages at the top of the bars.

Figure 5

Graph showing the magnitude of postoperative refractive astigmatism in the ray tracing group at 12 months posttreatment. Notes: At 12 months posttreatment, 81% of eyes had <0.50 D of cylinder. The red bars show preoperative astigmatism and the blue bars show postoperative astigmatism; the actual number of patients is represented by the percentages at the top of the bars. Abbreviation: D, diopter.

Figure 6

Graph of spherical equivalent refractive error in the ray tracing group through 12 months of follow-up.

Figure 7

Graph showing the predictability of the spherical equivalent refraction in the ray tracing group at 12 months posttreatment. Notes: The green dots indicate a spherical equivalent refraction within 0.5 D of the target refraction; the red dot signifies an overcorrection in one eye (5%). The blue dots represent an undercorrection in three eyes (14%). Abbreviations: D, diopter; SE, spherical equivalent.