Vector Analysis of Compound Myopic Astigmatism Using 2 Wavefront-Guided Excimer Platforms
Narrative Responses:
Purpose
To compare the astigmatic outcomes of laser in situ keratomileusis (LASIK) with two wavefront-guided (WFG) excimer lasers.
Methods
One hundred eyes of 50 patients underwent WFG-LASIK for compound myopic astigmatism. One eye underwent WFG-LASIK with the Alcon Wavelight Allegretto Eye-Q 400 laser platform, and the contralateral eye underwent WFG-LASIK with the AMO VISX Star S4IR platform. Preoperative and postoperative assessments were performed and included manifest refraction, vector analysis, topographic analysis, and wavefront aberrometry analysis. Eyes were stratified for subgroup analysis based on preoperative manifest astigmatism: 0.25-1, 1.25-2.25, and 2.5-3.5 diopters. Statistics were calculated using t-tests.
Results
Preoperatively, mean spherical equivalent (SE) was -3.9±1.7 vs -4.2±1.8 diopters (D) (p=0.03), and mean cylindrical error(CE) was 0.8±0.7 vs 0.8±0.8D (p=0.49) in the Alcon-WFG and VISX-WFG groups, respectively. At postoperative month 12, mean SE was -0.2 ±0.2 vs -0.2±0.3D (p=0.78), and mean CE was 0.2±0.2 vs 0.1±0.2D (p=0.57), respectively.
Alpins vector analysis for the Alcon-WFG and VISX-WFG groups, respectively, was: surgically-induced-astigmatism (0.9±0.8 vs 0.8±0.7D, p=0.22), error-magnitude (0.1±0.2 vs 0.1±0.2D, p=0.96), error-angle (12±36 vs 12±32°, p=1), correction-index (1.1±0.2 vs 1±0.4, p=0.9), success-index (0.2±0.3 vs 0.3±0.5, p=0.85), and flattening-index (1±0.7 vs 0.9±0.8, p=0.58).
Subgroup analysis by preoperative astigmatism showed no significant differences.
Conclusion
Minimal difference in outcomes between Alcon-WFG and VISX-WFG platforms based on objective Alpins analysis of astigmatism.