Unwanted Astigmatism and High-order Aberrations One Year after Excimer and Femtosecond Corneal Surgery

Abstract

SIGNIFICANCE Small incision lenticule extraction (SMILE) is advanced as the most minimally invasive and least traumatic corneal procedure for correcting refractive errors using a single laser. Although SMILE obtains similar results to femtosecond laser in situ keratomileusis (LASIK) with spherical myopia, it has deficiencies in astigmatism correction. PURPOSE The purpose of this study was to compare refractive outcomes and high-order aberrations (HOAs) between SMILE and femtosecond LASIK corneal procedures at 1 year post-operative. METHODS Ninety-two patients (181 eyes) with myopia/myopic astigmatism underwent either SMILE (group 1) or femtosecond LASIK (group 2). The refractive target was to achieve emmetropia in all cases. Data were analyzed to determine significance of change in refraction and HOAs. Furthermore, astigmatism was subjected to vector analysis using the Thibos (calculation of change, Δ, in J 0 and J 45 values) and Alpins (calculation of difference, ΔC, between target-induced astigmatism [TIA] and surgically induced astigmatism) methods. RESULTS Forty-five patients (89 eyes) from group 1 and 47 patients (92 eyes) from group 2 completed the study. The main significant (P ≤ .001) findings were as follows: (a) residual astigmatism was greater in group 1; (b) group 1, ΔJ 0 = 1.015J 0 + 0.040 (R = 0.861), ΔJ 45 = 1.082J 45 + 0.019 (R = 0.792), ΔC = 0.401TIA + 0.323 (R = 0.489), and mean spherical aberration increased from −0.003 (SD, ±0.059; 95% confidence interval [CI], −0.015 to 0.009) to 0.028 μm (SD, ±0.041; 95% CI, −0.037 to −0.020); and (c) group 2, ΔJ 0 = 0.952J 0 − 0.005 (R = 0.921), ΔJ 45 = 0.962J 45 − 0.002 (R = 0.923), ΔC = 0.187TIA + 0.101 (R = 0.272), mean coma reduced from 0.114 (SD, ±0.087; 95% CI, 0.096 to 0.132) to 0.077 μm (SD, ±0.059; 95% CI, 0.065 to 0.089), and trefoil from 0.089 (SD, ±0.049; 95% CI, 0.079 to 0.0990) to 0.056 μm (SD, ±0.047; 95% CI, 0.046 to 0.066). CONCLUSIONS In comparison with SMILE, femtosecond LASIK offered better precision in the overall control of astigmatism and HOAs.

Excimer Laser Corneal Refractive Surgery in the Clinic: A Systematic Review and Meta-analysis

“…Excimer laser, which originated in early 1970, is an excited dimer laser, which is a combination of compressed inert gas and halogen gas and excited by external energy to form an extremely unstable compound dimer excimer laser [ 24 ]. In the past ten years, laser in situ keratomileusis (LASIK), laser epithelial keratomileusis (LASEK), epipolis laser in situ keratomileusis (Epi-LASIK) and intra-laser assisted laser in situ keratomileusis (Intra-LASIK) have appeared successively in excimer laser in situ keratomileusis and then returned to the corneal surface to form the development pattern of the coexistence of deep corneal refractive surgery represented by LASIK and surface corneal refractive surgery represented by Epi-LASIK in the next few years [ 25 , 26 ].…”

“…In the early stage of the development of excimer laser corneal refractive surgery technology, the excimer laser therapeutic instruments produced by most manufacturers adopted the wide-band cutting method of large light spot [ 26 ]. This large light spot technology often leads to the following problems: central island effect, corneal opacity, and large light spot treatment, which determines in principle that there are certain limitations when treating hyperopia and astigmatism.…”

Effect of Postoperative Ocular Residual Astigmatism (ORA) on Treatment Outcome After Myopic Laser in situ Keratomileusis (LASIK)

“…3 Although there exist alternative options like small incision lenticule extraction (SMILE), 4 with a similar refractive outcome 5 also in the long term, 6 LASIK still remains an often-used reliable option. 7 Particularly focusing on the treatment outcome of myopic astigmatism patients, LASIK was comparatively to SMILE investigated to be superior to the control of astigmatism and HOAs (high-order aberrations). 7 …”

“… 7 Particularly focusing on the treatment outcome of myopic astigmatism patients, LASIK was comparatively to SMILE investigated to be superior to the control of astigmatism and HOAs (high-order aberrations). 7 …”

Corneal morphological changes after small incision lenticule extraction for myopic anisometropia

“…Changed corneal morphology and higher-order aberrations (HOAs) after SMILE have been reported (17)(18)(19). However, it was rarely reported whether the corneal morphological changes after SMILE are characteristic in the two eyes of a patient with anisometropia.…”