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With- or against-the-rule astigmatism, does it matter in SMILE surgery?

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Session Details

Session Title: Presented Poster Session: Keratorefractive Results II

Venue: Poster Village: Pod 2

First Author: : A.Ivarsen DENMARK

Co Author(s): :    J. Hjortdal              

Abstract Details


To determine the influence of cylinder axis on the postoperative outcome after small incision lenticule extraction (SMILE) for myopic astigmatism.


University Eye Clinic.


Seven hundred sixty-six eyes of 401 patients (249 female, 152 male, median age 34 years) were treated with SMILE for myopia with a cylinder of 0.75 diopters (D) or more. SMILE was performed with a Visumax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Patients were evaluated before and three months after surgery. Subjective refraction was converted to polar values and the achieved cylinder correction was calculated.


Preoperative cylinder averaged -1.5D (-0.75 to -5.75D). With-the-rule astigmatism (WTR) was observed in 71% and against-the-rule astigmatism (ATR) in 16%, irrespective of the cylinder magnitude. SMILE caused an average undercorrection of 0.22D, increasing with higher attempted correction. Average undercorrection was 0.31D in WTR, whereas ATR overcorrected 0.04D (p<0.001). Higher variance was observed in WTR than ATR (p<0.001). Undercorrection of 0.5D or more was observed in 28% (WTR) and 6% (ATR) (p<0.001). Overcorrection of 0.5D or more was seen in 3% (WTR) and 8% (ATR) (p=0.02). Differences between WTR and ATR were similar for low or high cylinders.


SMILE for myopic astigmatism shows higher variation and more undercorrection in WTR than in ATR astigmatism. The magnitude of the preoperative cylinder does not influence the observed differences between WTR and ATR. However, as previously demonstrated, increasing undercorrection is observed with higher attempted cylinder correction.

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