A comparison of induced astigmatism in conventional and wavefront-guided myopic LASIK using LADARVision4000 and VISX S4 platforms

PURPOSE: To evaluate and compare the surgically induced astigmatism in myopic eyes undergoing conventional and wavefront-guided LASIK. METHODS: A retrospective review was performed of the charts of 200 myopic eyes of 121 patients who underwent either custom or conventional treatments via the VISX S4 or LADARVision4000 platforms (50 consecutive eyes in each of the four groups). The primary outcome measure was manifest refraction, which was evaluated preoperatively and at 3 months postoperatively. The magnitude and axis of the unintended surgically induced astigmatism were calculated using vector analysis. The Student t test was used to compare the magnitudes of the surgically induced astigmatism and the absolute angle of error. RESULTS: The mean preoperative manifest cylinder was 0.66±0.38 diopters (D) for conventional VISX S4 and 0.68±0.39 D for VISX CustomVue (P=.795), and 0.76±0.56 D for LADARVision and 0.61±0.36 D for LADAR CustomCornea (P=. 114). The success index was 0.19±0.41 for VISX S4 and 0.49±0.49 for VISX CustomVue(P=.0013),and0.25±0.47for LADARVision and 0.20±0.39 for LADAR CustomCornea (P=.5721). The absolute mean angle of error was 4.4±13.9° for VISX S4 versus 14.9±23.9° for VISX CustomVue (P=.0085), and 6.1±12.3° for LADARVision versus 3.9±11.1° for LADAR CustomCornea (P=.3501). Of the VISX CustomVue eyes, 32% had an absolute angle of error >10°, as compared to 10% for both the VISX S4 and LADAR CustomCornea eyes (P=.013), and 16% for the LADARVision group (P=.056). CONCLUSIONS: Wavefront-guided ablation is associated with higher surgically induced astigmatism and larger astigmatic axis shift on the VISX platform as compared to the LADAR CustomCornea and the LADAR and VISX conventional platforms. Care should be emphasized mainly during registration/alignment to minimize surgically induced astigmatism in wavefront-guided LASIK.