الفهرس 
The excimer laserOnly 14 pages are availabe for public view
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Abstract
Purpose:
To compare visual acuity, refractive and topographic outcome between small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted in situ keratomileusis (WFG FS-LASIK) in patients with myopic astigmatism.
Design:
A prospective, non-randomized, comparative clinical study applied on patients with simple or compound myopic astigmatism.
Patients and methods:
The study included 60 eyes of patients with simple or compound myopic astigmatism presenting for refractive error correction. Femtosecond assisted LASIK group included 30 eyes and SMILE group included 30 eyes.
The following tests were done for all patients preoperatively and at 3 months postoperatively: full ophthalmological examination, manifest refraction, UDVA, CDVA, corneal topography using combined schimflug and placcido disc imaging namely Pentacam. (Oculus Inc.) and wavefront analysis using ATLAS 9000 (Carl Zeiss Meditec)
Main Outcome Measures:
Uncorrected distance visual acuity (UDVA), corrected disctance visual acuity (CDVA), manifest refraction, Efficacy, safety, predictability, corneal higher order aberrations.
Results:
The mean preoperative spherical equivalent was -4.83 ± 1.49 in SMILE group and -2.31 ± 1.22 in FS-LASIK group with a statistically significant difference between both groups (P < 0.05 ), the mean preoperative cylinder was -1.52 ± 0.91 in SMILE group and -1.48 ± 0.94 in FS-LASIK group with no statistically significant difference ( P = 0.940 ).
At 3 months, the mean MRSE in SMILE group was -0.33 ± 0.34 and the mean MRSE in FS- LASIK group was 0.23 ± 0.35 and there was a statistically significant difference between both groups (P < 0.05). mean postoperative cylinder was -0.56 ± 0.28 in SMILE group and -0.53 ± 0.38 in FS-LASIK with statistically significant difference ( P = 0.254 )
93% and 93% of eyes in the SMILE and FS-LASIK groups were within ± 0.5 D; 96.67% and 100% of eyes in the SMILE and FS-LASIK groups, respectively, were within ± 1 D.
There were 86.66% of treated eyes in the SMILE group, and 93.33% treated eyes in the FS-LASIK group that had 20/25 or better UDVA. There were 96.66% of treated eyes in the SMILE group, and 100% treated eyes in the FS-LASIK group, that had 20/30 or better UDVA with non-statistically significant difference of UDVA (P = 0. 554). Regarding safety, the CDVA in the SMILE group, 20 eyes (66.67%) showed no change, 8 eyes (27%) gained 1 line, 2 eyes (7%) lost 1 line, and no eyes lost more than 1 line. whereas in the FS-LASIK group, 27 eyes (90%) exhibited no change, 2 eyes (6.66%) gained 1 line, 1 eye (3.33%) lost 1 line, and no eyes lost more than 1 line and There was no statistically significant difference between both groups (P = 0. 554 ).
Regarding corneal asphericity, both procedures increased Q-value but there was no statistically significant difference between both groups in Δ Q value with FS-LASIK inducing more oblate anterior corneal shape (P = 0. 052). Regarding corneal higher order aberrations, both procedures significantly increased total conreanl aberrations but there was no statistically significant difference in the change in RMS of total corneal higher order aberration (P = 0.434) .but SMILE increased RMS of coma aberration significantly more than FS-LASIK (P = 0. 029).
Conclusion:
In this study, both SMILE and FS-LASIK procedures have shown excellent efficacy, safety, and predictability for the correction of myopia and myopic astigmatism. SMILE was closer to emmetropia regarding sphere and spherical equivalent, However, astigmatic undercorrection was noted after both surgeries with increased astigmatism. Both procedures increased the total corneal higher order aberrations with no statistically significant difference between both groups. A higher vertical coma was found in SMILE than WFG FS-LASIK. There was also no statistically significant difference in corneal asphericity change between both groups.
Limitation in our study: there was a significant difference in the preoperative manifest sphere and spherical equivalent in both groups. It is necessary to confirm these results with further studies with a larger numbers of eyes and a longer follow-up period. In addition, preoperative spherical and cylindrical diopter should be considered as a grouping
criterion in the patient population.