Abstract:Almost 25% of the variation after small-incision lenticule extraction for myopic astigmatism might be explained by the size of the attempted cylinder correction and ATR/WTR astigmatism. Incorporating these parameters in preoperative planning might produce more consistent results in high cylinder corrections.
“…51 A recent study using vector analysis concluded that almost 25% of the variation after SMILE for myopic astigmatism might be explained by the size of the attempted correction and the axis of the astigmatism, where SMILE induced 0.35 D less undercorrection in against-the-rule (ATR) than in WTR astigmatism. 52 The study also suggested an intended overcorrection of up to 0.125 D per diopter of attempted cylinder correction and a constant 0.25 D undercorrection in ATR astigmatism, irrespective of the attempted cylinder correction. 52…”
Section: Factors Affecting Astigmatism Correction Using Smilementioning
confidence: 66%
“…52 The study also suggested an intended overcorrection of up to 0.125 D per diopter of attempted cylinder correction and a constant 0.25 D undercorrection in ATR astigmatism, irrespective of the attempted cylinder correction. 52…”
Section: Factors Affecting Astigmatism Correction Using Smilementioning
Small incision lenticule extraction (SMILE) was introduced in the recent decade for the treatment of myopia and myopic astigmatism. This flap-free technique has a high efficacy and safety profile and also carries potential advantages over laser in situ keratomileusis such as a better corneal biomechanical stability, reduction in dry eyes rate, and the avoidance of flap complications. However, there have been concerns regarding the precision of astigmatism correction that undercorrection has been reported to be apparent. Various factors that affect astigmatism correction have been identified in the literature. The purpose of this review is to discuss the factors that affect astigmatism correction in SMILE and several techniques to improve the refractive outcomes.
“…51 A recent study using vector analysis concluded that almost 25% of the variation after SMILE for myopic astigmatism might be explained by the size of the attempted correction and the axis of the astigmatism, where SMILE induced 0.35 D less undercorrection in against-the-rule (ATR) than in WTR astigmatism. 52 The study also suggested an intended overcorrection of up to 0.125 D per diopter of attempted cylinder correction and a constant 0.25 D undercorrection in ATR astigmatism, irrespective of the attempted cylinder correction. 52…”
Section: Factors Affecting Astigmatism Correction Using Smilementioning
confidence: 66%
“…52 The study also suggested an intended overcorrection of up to 0.125 D per diopter of attempted cylinder correction and a constant 0.25 D undercorrection in ATR astigmatism, irrespective of the attempted cylinder correction. 52…”
Section: Factors Affecting Astigmatism Correction Using Smilementioning
Small incision lenticule extraction (SMILE) was introduced in the recent decade for the treatment of myopia and myopic astigmatism. This flap-free technique has a high efficacy and safety profile and also carries potential advantages over laser in situ keratomileusis such as a better corneal biomechanical stability, reduction in dry eyes rate, and the avoidance of flap complications. However, there have been concerns regarding the precision of astigmatism correction that undercorrection has been reported to be apparent. Various factors that affect astigmatism correction have been identified in the literature. The purpose of this review is to discuss the factors that affect astigmatism correction in SMILE and several techniques to improve the refractive outcomes.
“…11 Undercorrection reported in previous studies ranges from around 10–15% which is in agreement with our study. 8 – 10 , 12 , 31 – 34 Figure 3 Comparison of vector analysis outcomes with other studies. …”
Section: Discussionmentioning
confidence: 98%
“…Iversen et al found a difference of around 0.35 D in postoperative cylinder between WTR and ATR correction, and suggested adding 0.125 D per diopter of WTR astigmatism and a constant 0.25 D undercorrection of ATR astigmatism. 31 …”
Purpose
To assess a single site’s initial experience with SMILE for the treatment of myopic astigmatism and compare outcomes and vector analysis results with the US Food and Drug Administration (FDA) results and published literature.
Patients and Methods
Forty-eight eyes (29 patients) with mean preoperative sphere of −5.11 ± 1.31 diopters (D) and cylinder of −1.12 ± 0.60 D underwent SMILE. Visual acuity, refractive, and vector analysis outcomes as well as subjective measures were reported at three and twelve months postoperatively and compared with FDA results and the published literature between 2014 and 2020 involving treatment of patients with mean cylinders of >−0.50 to ≤−3.00 D.
Results
At three and twelve months, 43 and 32 eyes were evaluated, respectively. At twelve months, mean cylinder power was reduced to −0.38 ± 0.38 D with 78.1% achieving ≤±0.50 D. Uncorrected distance visual acuity (UDVA) ≥20/20 was achieved in 77.4% of eyes by twelve months with 100% achieving ≥20/30 UDVA. No loss of corrected distance visual acuity was observed in eyes seen at twelve months. Correction index (CI) at twelve months was 0.90 indicating overall undercorrection of 10%. Twelve-month CI was 0.96, 0.90, and 0.83 in eyes with preoperative cylinders of <−1.00 D, ≥−1.00 to <−2.00 D, and ≥−2.00 D, respectively. Mean angle of error was −1.58 ± 11.61° ranging from −24.22° to 37.75°.
Conclusion
We found SMILE to be an effective and safe means of achieving spectacle independence and improving visual acuity in patients with myopic astigmatism. SMILE has the potential for improved clinical outcomes with better nomogram guidance and advancements in technique. However, surgeons must be aware of the potential for undercorrection in with-the-rule astigmatism and at higher preoperative cylinders and as well as the potential for overcorrection in against-the-rule and lower preoperative cylinder astigmatism.
“…19 Besides, there are other factors that may in uence astigmatic correction by SMILE, including ocular residual astigmatism, angle kappa, anterior corneal curvature, preoperative axis of astigmatism, and the technique of lenticule extraction. 13,[20][21][22][23] Several adjustments of current treatment nomograms have been suggested, leading to a 10% increment in the magnitude of astigmatism correction. 4,24 Currently, however, there are no standardized nomograms for astigmatism correction.…”
Background: To evaluate clinical outcomes after full-thickness astigmatic keratotomy (FTAK) combined with small-incision lenticule extraction (SMILE) in eyes with high astigmatism.Methods: This study comprised 75 eyes of 43 patients with over 4.0 diopters (D) of astigmatism who were treated with SMILE after FTAK. Visual acuities and refractive measurements were evaluated at 1 month after FTAK, and 1, 6, 12, and 24 months after SMILE. Vector analysis of the astigmatic changes was performed using the Alpins method.Results: Twenty-four months after the combined procedure, the average spherical equivalent was reduced from -6.56 ± 2.38 D to -0.36 ± 0.42 D (p < 0.001). The uncorrected and corrected distance visual acuities improved from 1.54 ± 5.53 to -0.02 ± 0.09 and from -0.03 ± 0.07 D to -0.07 ± 0.08 D (both p < 0.001), respectively. The preoperative mean astigmatism was -5.48 ± 1.17 D, which was reduced to -2.27 ± 0.97 D and -0.34 ± 0.26 D at 1 month after FTAK and 24 months after SMILE, respectively (p <0.001). The surgically-induced astigmatism after FTAK, SMILE, and FTAK and SMILE combined was 3.38 ± 1.18 D, 2.22 ± 0.84 D, and 5.39 ± 1.20 D, respectively. Furthermore, the correction index of FTAK, SMILE, and FTAK and SMILE combined was 0.63 ± 0.17, 0.90 ± 0.40, and 0.98 ± 0.06, respectively. There were no intraoperative or postoperative complications. Conclusion: Our surgical procedure combining FTAK and SMILE showed good and stable clinical outcomes during two-year follow-up for the treatment of high astigmatism.
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