Femtosecond Laser-assisted Laser In Situ Keratomileusis Group Research Articles

Comparison of early visual outcomes after low-energy SMILE, high-energy SMILE, and LASIK for myopia and myopic astigmatism in the United States.

To compare uncorrected distance visual acuities (UDVAs) and induced higher-order aberrations (HOAs) in the early postoperative period between low-energy (LE) small-incision lenticule extraction (SMILE), high-energy (HE) SMILE, and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) procedures. University based refractive surgery center. Retrospective cohort study. Records of patients who underwent SMILE or FS-LASIK were retrospectively reviewed. SMILE patients were separated into 2 groups: HE settings (125 nJ, 3.0 μm spot spacing) and LE settings (125-130 nJ, 4.5 μm spot spacing). UDVA was measured at postoperative day (POD) 1. Corneal HOAs and UDVA were measured at postoperative month (POM) 1. Induced spherical aberration, vertical coma, horizontal coma, total coma, and total HOAs were calculated. The study included 147 eyes of 106 patients, 49 in each group. For SMILE patients, the difference in mean UDVA at POD1 was highly statistically significant in favor of the LE group (-0.003 vs 0.141, P < .0001). No significant difference in mean UDVA at POD1 was noted between the LE group and FS-LASIK group (-0.003 vs -0.011, P = .498). Induced change in spherical aberration was less in LE SMILE than that in FS-LASIK (0.136 vs 0.186 μm, P = .02) at POM1. No significant differences in POM1 mean UDVA (-0.033 vs -0.036) or induced change in all other HOAs were noted between LE SMILE and FS-LASIK. LE settings were associated with significantly improved POD1 UDVA. POD1 and POM1 UDVA were comparable with those of FS-LASIK. Spherical aberration induction was less with LE SMILE than that with FS-LASIK, whereas all other induced HOAs were comparable with FS-LASIK.

Comparison of clinical results between trans-PRK and femtosecond LASIK for correction of high myopia

BackgroundTo compare the clinical outcomes of transepithelial photorefractive keratectomy (TPRK) with femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for correction of high myopia.MethodsIn this prospective, non-randomised, cohort study, 85 eyes of 46 patients treated with TPRK and 80 eyes of 42 patients treated with FS-LASIK were included. All eyes were highly myopic (spherical equivalent refraction <− 6.00 diopters). Both TPRK and FS-LASIK were performed by Schwind Amaris 750S excimer laser. Visual acuity, refraction, corneal high order aberration (HOA) and other variables were analyzed before and at 1, 3, 6, 12 months after surgery.ResultsAt 12 months after surgery, uncorrected logMAR distance visual acuity (UDVA) in the TPRK and FS-LASIK groups was − 0.04 ± 0.04 and − 0.01 ± 0.08, respectively (P = 0.039). Corrected logMAR distance visual acuity (CDVA) was − 0.06 ± 0.05 and − 0.04 ± 0.05 in both groups (P = 0.621). For UDVA, 86% of eyes in the TPRK group and 80% in the FS-LASIK group remained unchanged or improved one or more logMAR lines (P = 0.314), compared to preoperative CDVA. For CDVA, 97% of eyes in the TPRK group and 90% in the FS-LASIK group remained unchanged or improved one or more lines (P = 0.096), compared to preoperative CDVA. Spherical equivalent refraction was − 0.05 ± 0.39 and − 0.26 ± 0.47 in both groups (P = 0.030). 87% of eyes in the TPRK group and 73% in the FS-LASIK group achieved ±0.50 D target refraction (P = 0.019). All 85 eyes (100%) in the TPRK group and 75 eyes (92%) in the FS-LASIK group were within ±1.00 D of target (P = 0.003). Root mean square (RMS) of corneal total HOA and vertical coma in the TPRK group were lower compared with the FS-LASIK group (P < 0.001 for both variables).ConclusionsTPRK and FS-LASIK showed good safety, efficacy and predictability for correction of high myopia. Clinical outcomes of TPRK were slightly better than FS-LASIK.

Changes in Corneal Volume at Different Areas and Its Correlation with Corneal Biomechanics after SMILE and FS-LASIK Surgery.

Purpose To investigate the variations of corneal volume (CV) after small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and analyze the influences of biomechanical properties on the changes of refraction and CV. Methods Ninety-seven eyes of 97 patients undergoing SMILE and FS-LASIK were included in this retrospective study. CV was measured with Scheimpflug-based corneal topography at preoperatively and at day 1, week 1, and months 1 and 3 postoperatively. CV measured within 5 mm diameter was defined as central region volume (CV5) and between 5 mm and 10 mm diameter was defined as peripheral region volume (CV5-10). An Ocular Response Analyzer (ORA) was used to assess corneal biomechanical properties including corneal hysteresis (CH) and corneal resistant factor (CRF). The reduction of study parameters (△) were calculated by subtracting the preoperative value at various time points from the postoperative values. Results CV had significant reduction after the SMILE and FS-LASIK procedure (P < 0.05). CV5 increased significantly from postoperative day 1 to month 3 (P < 0.001) in SMILE, while both CV5 and CV5-10 increased significantly in FS-LASIK (P < 0.001). The increase in CV5 after SMILE was 0.11 ± 0.16 mm3，which was significantly different from FS-LASIK (0.20 ± 0.13 mm3, P=0.004). In the SMILE group, △CV5 correlated with △CRF (r = 0.498, P < 0.001) and △CH (r = 0.374, P=0.007). In the FS-LASIK group, △CV5 and △CRF had a significant correlation (r = 0.363, P=0.012), but not with △CH. Conclusions Dynamic changes in corneal volume were found after SMILE and FS-LASIK surgery. The central region significantly increased after SMILE, while both central and peripheral regions increased following FS-LASIK in the early postoperative period. SMILE was associated with less change in biomechanical properties per unit of reduction in CV compared with FS-LASIK.

Visual Outcomes after Small Incision Lenticule Extraction and Femtosecond Laser-Assisted LASIK for High Myopia

Purpose: The aim of this study was to compare visual outcomes after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for high myopia. Methods: In this prospective, comparative study, a total of 52 eyes of 34 consecutive highly myopic patients with spherical equivalent within the range of –8.00 to –10.00 diopters were recruited. Twenty-three eyes of 16 patients were in the FS-LASIK group and 29 eyes of 18 patients were in the SMILE group. Visual outcomes and wavefront aberrations were analyzed preoperatively and 6 months postoperatively. Results: At the postoperative 6-month visit, 96.6% in the SMILE group and 91.3% in the FS-LASIK group achieved unchanged or better corrected distance visual acuity (CDVA). As for uncorrected distance visual acuity (UDVA), 96.6% in the SMILE group and 95.7% in the FS-LASIK group achieved UDVA of 20/20 or better. As for wavefront aberrations, high-order aberrations (HOAs) and spherical aberrations increased significantly after surgery in both groups relative to corresponding preoperative values (p < 0.001), and vertical coma increased after SMILE (p < 0.001). No statistically significant differences in changes of HOAs (p =0.90), spherical aberrations (p = 0.07), horizontal coma (p = 0.56), coma (p =0.08), horizontal trefoil (p =0.19), vertical trefoil (p = 0.90), and trefoil (p = 0.45) were detected between the 2 groups, except for vertical coma (p < 0.01). Conclusions: SMILE is as effective as FS-LASIK in correcting high myopia, but attention should be paid to the induction of vertical coma in highly myopic patients following a SMILE procedure.

Visual and optical quality outcomes of SMILE and FS-LASIK for myopia in the very early phase after surgery

BackgroundSmall incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) are frequently used to treat myopia. However, little is known about the impact on recovery of these approaches in the very early postsurgical phase (within 24 h).MethodsTo compare the efficacy of these two procedures for the treatment of myopia in the early phase after surgery, differences in visual acuity, OSI (objective scattering index), cutoff for modulation transfer function (MTF), and SR (Strehl ratio) between SMILE and FS-LASIK were evaluated at 0, 2, 4 and 24 h postoperatively using two-way analysis of variance (ANOVA).ResultsNo significant differences between SMILE and FS-LASIK in the MTF cutoff and SR were found (p > 0.05). However, at 2 h and 4 h after surgery, OSI values in the SMILE group were significantly higher than those in the FS-LASIK group, and visual acuity scores in the SMILE group were significantly poorer than those in the FS-LASIK group (p < 0.05). Regarding subjective symptoms, the number of patients complaining of eye dryness, blurred vision, foreign body sensation and eye soreness in the SMILE group were lower than the number in the FS-LASIK group.ConclusionsIn conclusion, visual and optical quality outcomes of FS-LASIK for myopia were better than those of SMILE in the very early phase after surgery, a difference that is attributable to the formation of interface haze.Trial registrationChiCTR1900021451.

Early changes in posterior corneal elevation and related factors after femtosecond laser assisted LASIK and SBK

Objective To compare the early change of posterior corneal elevation with femtosecond laser assisted laser in situ keratomileusis (FS-LASIK) and sub-Bowman keratomileusis (SBK) by Oculyzer and analyze the related factors after FS-LASIK. Methods A longitudinal observational study was designed.Ninety-one eyes of 46 patients with myopia or myopic astigmatism in the First Affiliated Hospital of Anhui Medical University from January to April in 2016 were divided into FS-LASIK group (53 eyes of 27 patients), SBK group (38 eyes of 19 patients) according to the patients' wishes and each part of corneal elevation change values were explored after FS-LASIK and SBK surgeries.The posterior corneal elevation was measured at twenty-seven measuring points along the central, paracentral, midperipheral and peripheral zone (vertex and 1, 2 and 3 mm radius) using Oculyzer preoperatively, l day, 7 days and 1 month postoperatively, respectively.Written informed consent was obtained from each patient before the surgery. Results In the FS-LASIK group, the posterior corneal elevation difference values in the central zone were (-0.924±1.859), (-1.151±1.586) and (-0.940±1.994)μm 1 day, 7 days and 1 month postoperatively, respectively.In the periphery zone, the elevation difference values were (1.046±1.667), (1.172±1.566) and (1.023±1.622)μm.In the paracentral and midperipheral zone, the cornea displayed slightly backward or forward shift.In SBK group, the posterior corneal elevation difference values of the vertex were (-0.684±1.454), (-1.053±1.723) and (-0.553±1.572)μm 1 day, 7 days and 1 month after operation, respectively.In the paracentral and midperipheral zone displayed the same trend with FS-LASIK group, and in the periphery, the values were (1.207±1.317), (1.327±1.529) and (1.208±1.415)μm.There were no statistically significant differences in posterior corneal elevation between the two surgery modes among the three time points (all at P>0.05). At 1 month postoperatively, only two independent variables, which were spherical equivalent (SE) and ablation depth (AD) entered the regression in the central and paracentral zones.Independent variables, such as central thinnest corneal thickness (TCT), SE, AD, residual bed thickness (RBT) and the ratio of AD and TCT (AD/TCT) did not enter the regression in other two areas. Conclusions The posterior corneal elevation in the central 6 mm area shows tiny change in the early stage and the variation is larger 7 days after operation in the two groups, but it does not result in keratectasia.With the increase of SE and AD, the posterior corneal elevation is more likely to be affected. Key words: Myopia; Femtosecond laser assisted laser in situ keratomileusis; Sub-Bowman keratomileusis; Posterior corneal elevation; Oculyzer

Corneal densitometry and topography after femtosecond laser-assisted laser in-situ keratomileusis compared with small-incision lenticule extraction

Purpose The aim of this study was to compare between femtosecond laser-assisted laser in-situ keratomileusis (FS-LASIK) and small-incision lenticule extraction (SMILE) regarding corneal densitometry (CD) and corneal topography. Setting The study was conducted at Department of Ophthalmology, Faculty of Medicine, University of Alexandria, Alexandria, Egypt. Patients and methods The study included 60 eyes of 30 patients divided into two equal groups: 30 eyes were treated using FS-LASIK and 30 eyes were treated using SMILE surgery for myopia and myopic astigmatism to evaluate CD and topography before and after 1 week and 2 months postoperatively using Pentacam HR. Results There was an insignificant difference between the two groups in CD preoperatively (P=0.154), 1 week postoperatively (P=0.180), and 2 months postoperatively (P=0.138). In FS-LASIK group, there was a significant flattening in keratometric values (K1 and K2) of anterior corneal surface as the mean of K1 was 36.33±1.45 and 36.24±1.43 D and the mean of K2 was 37.09±1.55 and 37.00±1.52 D in comparison between 1-week postoperative and 2-month postoperative follow-up visits, respectively. There was an insignificant difference between the two groups in K1 and K2 of the posterior surface preoperatively, 1 week postoperatively, and 2 months postoperatively. Conclusion There was an insignificant difference between the two groups in CD. In the anterior surface, FS-LASIK exhibited more flattening in K1 and K2 than SMILE. Regarding the posterior surface, there was an insignificant difference between FS-LASIK and SMILE.

Comparison of effective optical zone after small-incision lenticule extraction and femtosecond laser–assisted laser in situ keratomileusis for myopia

To compare the effective optical zone (EOZ) after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted laser insitu keratomileusis (FS-LASIK). Jinan Mingshui Eye Hospital, Jinan, China. Retrospective case series. Myopic patients who had small-incision lenticule extraction or FS-LASIK were enrolled in this retrospective study. Effective OZs were measured at 1week, 1month, and 3months postoperatively, using the tangential curvature difference map of the Scheimpflug tomography system. Correlations between the changes in the EOZ and relevant parameters were analyzed 3months postoperatively. The study comprised 76 patients (76 eyes). The mean EOZs at 1week, 1month, and 3months postoperatively were 5.39±0.27 mm, 5.33±0.30mm, and 5.34±0.23mm in the small-incision lenticule extraction group and 5.06±0.36mm, 4.98±0.39mm, and 5.01±0.31mm in the FS-LASIK group, when the programmed OZ was 6.5mm. The magnitude of decreases in EOZ was significantly smaller in the small-incision lenticule extraction group than in the FS-LASIK group at all timepoints after surgery (P<.01). There were significant correlations between changes in EOZ and corneal asphericity (P<.01). Epithelial thickening was positively correlated with EOZ reduction in the small-incision lenticule extraction group (r=0.479, P<.01); however, no correlation was found between epithelial thickening and EOZ reduction in the FS-LASIK group (r=.324, P>.05). Both small-incision lenticule extraction and FS-LASIK resulted in EOZ reduction during correction of myopia. However, small-incision lenticule extraction resulted in less reduction than FS-LASIK and was associated with corneal asphericity changes and epithelial thickening.

Three-year outcomes of small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for myopia and myopic astigmatism

AimsTo compare long-term clinical outcomes following small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for myopia and myopic astigmatism correction.MethodsIn this retrospective study, we enrolled a total of 101 patients (101 eyes) who underwent SMILE or FS-LASIK 3 years prior. Measured parameters included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction and corneal wavefront aberrations.ResultsNo significant differences in patient characteristics were found between the two groups. At the 3-year follow-up, UDVA was better than or equal to 20/20 in 90% and 85% (p=0.540) of the eyes; the efficacy indexes were 1.05±0.19 and 1.01±0.21 in the SMILE and FS-LASIK groups, respectively (p=0.352). Safety indexes were 1.19±0.17 and 1.15±0.20 in the SMILE and FS-LASIK groups, respectively (p=0.307). Eighty per cent and 65% of eyes were within ±0.50 D of the attempted spherical equivalent correction after SMILE and FS-LASIK, respectively (p=0.164). Vector analysis revealed no significant differences in astigmatic correction between the two groups (p>0.05). Surgically induced spherical aberration was higher in the FS-LASIK group than in the SMILE group (p<0.001).ConclusionLong-term follow-up analysis suggested that both SMILE and FS-LASIK were safe and equally effective for myopic and astigmatic correction.

Retinal nerve fiber layer thickness after laser-assisted subepithelial keratomileusis and femtosecond LASIK: a prospective observational cohort study.

PurposeBased on the assumption that high levels of intraocular pressure (IOP) during femtosecond laser-assisted in situ keratomileusis (FS-LASIK) may compromise the retinal nerve fiber layer (RNFL), newer femtosecond platforms that operate without causing significant IOP elevation have been developed in recent years. However, this assumption has not been adequately tested. The aim of the current study was to evaluate possible changes in RFNL thickness in nonglaucomatous myopic patients undergoing FS-LASIK using the 60 KHz IntraLase® device that significantly elevates the IOP for an appreciable period of time vs an advanced surface ablation technique (laser-assisted subepithelial keratomileusis, LASEK) that does not induce any IOP elevation.MethodsThis was a prospective, observational, controlled cohort study. One randomly selected eye of 114 consecutive eligible patients was analyzed. Inclusion criteria were myopia up to -6.00 diopters and astigmatism up to -2.00 diopters. As clinically indicated, 50 patients underwent LASEK and 64 underwent FS-LASIK. The RNFL thickness was determined with a spectral-domain optical coherence tomography device preoperatively and 3 months postoperatively by the same masked observer.ResultsThere was no significant difference in preoperative refractive error, age, or sex between the groups. Preoperatively, central corneal thickness was significantly lower in the LASEK group (529.1±36.1 vs 562.4±31.6 µm, P=0.001). For the LASEK group, there was no significant difference between preoperative and postoperative RNFL thickness in the studied sectors (superior-temporal, temporal, inferior-temporal, average). For the FS-LASIK group, compared to preoperative RNFL measures, statistically significant thicker postoperative values were found for the average RNFL (mean difference: 0.67 µm, 0.7% increase, P=0.008) and the inferior-temporal sector (mean difference: 0.92 µm, 0.6% increase, P=0.02).ConclusionLASIK with a femtosecond platform that induces high intraoperative IOP did not cause RNFL thinning. The observed differences between preoperative and postoperative values are below the axial resolution limit of optical coherence tomography devices.

Vector analysis of high (≥3 diopters) astigmatism correction using small-incision lenticule extraction and laser in situ keratomileusis

To compare the astigmatic correction in high myopic astigmatism between small-incision lenticule extraction and laser insitu keratomileusis (LASIK) using vector analysis. Hong Kong Laser Eye Center, Hong Kong. Retrospective case series. Patients who had correction of myopic astigmatism of 3.0 diopters (D) or more and had either small-incision lenticule extraction or femtosecond laser-assisted LASIK were included. Only the left eye was included for analysis. Visual and refractive results were presented and compared between groups. The study comprised 105 patients (40 eyes in the small-incision lenticule extraction group and 65 eyes in the femtosecond laser-assisted LASIK group.) The mean preoperative manifest cylinder was -3.42 D±0.55 (SD) in the small-incision lenticule extraction group and -3.47±0.49 D in the LASIK group (P=.655). At 3months, there was no significant between-group difference in uncorrected distance visual acuity (P=.915) and manifest spherical equivalent (P=.145). Ninety percent and 95.4% of eyes were within ± 0.5 D of the attempted cylindrical correction for the small-incision lenticule extraction and LASIK group, respectively (P=.423). Vector analysis showed comparable target-induced astigmatism (P=.709), surgically induced astigmatism vector (P=.449), difference vector (P=.335), and magnitude of error (P=.413) between groups. The absolute angle of error was 1.88±2.25 degrees in the small-incision lenticule extraction group and 1.37±1.58 degrees in the LASIK group (P=.217). Small-incision lenticule extraction offered astigmatic correction comparable to LASIK in eyes with high myopic astigmatism.

Three-year results of small incision lenticule extraction and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis for correction of high myopia and myopic astigmatism.

To compare and calculate the 3-year refractive results, higher-order aberrations (HOAs), contrast sensitivity (CS) and dry eye parameters after small incision lenticule extraction (SMILE) and wavefront-guided femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for correction of high myopia and myopic astigmatism. In this prospective, non-randomized comparative study, 78 eyes with spherical equivalent (SE) of -8.11±1.09 diopters (D) received a SMILE surgery, and 65 eyes with SE of -8.05±1.12 D received a wavefront-guided FS-LASIK surgery with the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) for flap cutting. Visual acuity, manifest refraction, CS, HOAs, ocular surface disease index (OSDI) and tear break-up time (TBUT) were evaluated during a 3-year follow-up. The difference of uncorrected distance visual acuity (UDVA) postoperatively was achieved at 1mo and at 3mo, whereas the difference of the mean UDVA between two groups at 3y were not statistically significant (t=-1.59, P=0.13). The postoperative change of SE was 0.89 D in the FS-LASIK group (t=5.76, P=0.00), and 0.14 D in the SMILE group (t=0.54, P=0.59) from 1mo to 3y after surgery. At 3-year postoperatively, both HOAs and spherical aberrations in the SMILE group were obviously less than those in the FS-LASIK group (P=0.00), but the coma root mean square (RMS) was higher in the SMILE group (0.59±0.26) than in the FS-LASIK group (0.29±0.14, P=0.00). The mesopic CS values between two groups were not statistically significant at 3y postoperatively. Compared with the FS-LASIK group, lower OSDI scores and longer TBUT values were found in the SMILE group at 1mo and 3mo postoperatively. With regard to safety, no eye lost any line of CDVA in both groups at 3y after surgery. Both SMILE and wavefront-guided FS-LASIK procedures provide good visual outcomes. Both procedures are effective and safe, but SMILE surgery achieve more stable long-term refractive outcome and better control of early postoperative dry eye as compared to FS-LASIK.

Comparison of changes in refractive error and corneal curvature following small-incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis surgery.

Purpose:To compare visual acuity, refractive error, corneal curvature, and the stability of these parameters during the early postoperative period following small-incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) surgery.Methods:One hundred and five eyes and 110 eyes were enrolled in SMILE and FS-LASIK group, respectively. Uncorrected and best-corrected distance visual acuity (UCVA and BCVA), manifest refraction, corneal curvature, intraocular pressure, and slit-lamp examinations were performed preoperatively, 1 day, 1 week, 1 month, and 3 months postoperatively.Results:No significant differences in postoperative UCVA or BCVA were observed between the SMILE and FS-LASIK groups at any time point. SMILE group had significant better postoperative spherical equivalent (SE) values than FS-LASIK group at 1 day, 1 week, and 1-month follow-up. However, there was no significant difference in postoperative SE values at 3-month follow-up. Significant differences in mean postoperative corneal curvature were observed during all follow-up examinations.Conclusion:SMILE surgery was associated with more accurate postoperative refractive correction up to 1 month following surgery. SMILE surgery also resulted in less significant corneal curvature changes than FS-LASIK. Furthermore, FS-LASIK was associated with decreased stability of postoperative refractive error and corneal curvature relative to SMILE.

Comparison of corneal ablation depth predictability between small incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis for myopia

Background Recently, small incision lenticule extraction (SMILE) procedure is used to correct myopia.The clinical safety and efficiency of SMILE have been approved, but its predictability to corneal ablation depth is brought into focus. Objective This study was to compare the predictability of ablation depth in central cornea between SMILE and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for myopia. Methods A non-randomized controlled clinical study was performed.Two hundred and seventy eyes of 135 myopic patients who were going to receive corneal refractive surgery were included in Beijing Tongren Hospital from October 2015 to May 2016.SMILE and FS-LASIK were performed on 138 eyes of 69 patients and 132 eyes of 66 patients matched in demography respectively under the informed consent.Central corneal thickness was measured by RTVue FD-OCT before and 1 week after surgery.The refractive power, actual ablation depth (difference of central corneal thickness before and after surgery) and central corneal cutting error (difference between theoretically expected ablation depth and real ablation depth) were intergrouply compared, and the correlation of real ablation depth with theoretically expected ablation depth was assessed. Results No significant difference was found in spherical power, astigmatic power and spherical equivalent after surgery between SMILE group and FS-LASIK group (t=-1.826, -1.405, -1.420, all at P>0.05). The actual ablation depth was (76.96±15.27)μm in the SMILE group, which was significant lower than (96.76±16.52)μm of theoretically expected ablation depth (t=-23.016, P<0.01); however, there was no significant difference in the FS-LASIK group between actual and expected ablation depth([77.92±18.69] μm versus [77.42±15.60] μm) (t=-0.604, P=0.547). The central corneal cutting error was (20.55±8.51)μm in the SMILE group and (7.17±5.97)μm in the FS-LASIK group, showing a significant difference between them (t=14.950, P<0.01). The positive linear correlations were seen between actual and expected ablation depth in both SMILE group and FS-LASIK group (r=0.799, 0.867, both at P<0.01). The actual ablation depth was increased over expected ablation depth, with the regression equations of Y=3.892+ 0.749X in the SMILE group and Y=3.443+ 0.957X in the FS-LASIK group. Conclusions The actual corneal ablation depth is less than expected corneal ablation depth in SMILE procedure, while in FS-LASIK procedure, the actual corneal ablation depth appears to be consistent with the expected one, inferring a good predictability in corneal ablation depth in FS-LASIK surgery. Key words: Myopia/surgery; Corneal stroma/surgery; Lasers, excimer/therapeutic use; Central corneal thickness; Ablated depth; Predictability; Comparative study

Dry eye and corneal sensitivity after small incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis: a Meta-analysis.

To assess the corneal sensitivity and the incidences of dry eye after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK). The Meta-analysis was performed using RevMan 5.3. We searched on PubMed from inception to March 2016. Summary weighted mean difference (WMD) and 95% confidence intervals (CIs) were used to analyze the datum. Random-effects or fixed-effects models were chosen up to between-study heterogeneity. The main outcomes were composed of the Ocular Surface Disease Index (OSDI) scores, tear film break-up time (TBUT), Schirmer Test and corneal sensitivity. Eight eligible studies including 772 eyes (386 in SMILE group and 386 in FS-LASIK group) were identified. The parameters have no significiant difference heterogeneity between SMILE and FS-LASIK group preoperatively. There were significant differences between the two groups in OSDI scores at one and three months postoperatively, in TBUT at one and three months postoperatively, in corneal sensitivity at one week, about one month and three months postoperatively. However, there was no significant difference observed in Schirmer Test at the follow-up periods. Compare to FS-LASIK, dry eye and the corneal sensitivity recover better in the SMILE group, in first three months after the surgery.

Dry Eye After Small Incision Lenticule Extraction and Femtosecond Laser-Assisted LASIK: Meta-Analysis.

To compare postoperative ocular surface integrity and innervation between small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). The Cochrane Central Register of Controlled Trials, PubMED, and EMBASE were searched for prospective comparative studies. Trials meeting the selection criteria were quality appraised, and the data were extracted by 2 independent authors. The weighted mean differences (WMDs) and 95% confidence intervals (CIs) were used to compare dry eye examinations and corneal subbasal nerve density (SMILE-FS-LASIK). The study covered 5 trials. No significant difference was found in the Schirmer test score between both groups (WMD = -1.91 and 0.27; 95% CI, -5.02 to 1.20 and -0.99 to 1.54; P = 0.23 and 0.67 at 1- and 6-month follow-ups, respectively). Tear breakup time in the SMILE group significantly exceeded that in the FS-LASIK group (WMD = 0.65 and 1.14; 95% CI, 0.20-1.10 and 0.18-2.10; P = 0.004 and 0.02, at 1- and 6-month follow-ups, respectively). Ocular surface disease index scores were significantly better in the SMILE group 6 months postoperatively (WMD = -10.12, 95% CI, -16.07 to -4.18, P = 0.0008). No significant difference was found in tear osmolarity between both groups (WMD = -5.19 and -6.37; 95% CI, -17.15 to 6.76 and -22.74 to 10.00; P = 0.39 and 0.45 at 1- and 6-month follow-ups, respectively). Higher corneal sensitivity was observed in the SMILE group 1 and 6 months postoperatively (WMD = 11.35 and 3.49; 95% CI, 7.29-15.40 and 1.76-5.21; P < 0.00001 and <0.0001, at 1- and 6-month follow-ups, respectively). Corneal subbasal nerve density was also significantly higher in SMILE-treated eyes than it was in FS-LASIK-treated eyes 1 month postoperatively (WMD = 4.72, 95% CI, 1.10-8.34, P = 0.01). According to this meta-analysis, the SMILE procedure has fewer negative impacts on the ocular surface and corneal innervation than does FS-LASIK. Furthermore, SMILE shows superiority over FS-LASIK by a exhibiting a lower risk of postoperative dry eye.

Vector analysis and comprison of small incision lenticule extraction versus laser in-situ keratomileusis for low to moderate myopic astigmatism

Background Small incision lenticule extraction (SMILE) is lack of eye-tracking system and there is controversy in the treatment of astigmatism.It is very important to understand its correction effctiveness for myopic astigmatism. Objective This study was to evaluate the clinical outcomes in the correction of myopic astigmatism between SMILE and femtosecond laser assisted laser in situ keratomileusis (FS-LASIK). Methods In this retrospective study, 95 eyes of 51 patients and 69 eyes of 40 patients with myopic astigmatism underwent the SMILE surgery and FS-LASIK surgery respectively in Tianjin Eye Hospital from December 2013 to July 2014 under the informed consent.No significant differences were found in spherical power, astigmatic power and spherical equivalent (SE) between the SMILE group and FS-LASIK group before surgery (all at P>0.05). The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest refraction, slit-lamp microscopy, intraocular pressure and corneal topography were measured before surgery and 1 day, 1 week, 1 month, 3 months after surgery.Vector analysis was used to calculate the components of astigmatism before and after surgery.Correction index (CI), index of success (IOS), angle of error (AofE) and flattening index (FI) were used to evaluate the correction effectiveness of astigmatism.Safety index and efficacy index were used to evaluate the recovery status of visual acuity.The corrected effectiveness was compared between the two groups, and the correlations of kappa angle with measured parameter were assessed by Spearman rank correlation analysis. Results The mean spherical power, astigmatic power and SE were (0.003±0.106), (-0.063 ± 0.126) and (-0.029 ± 0.101)D in the SMILE group, which were significantly lower than (0.112 ± 0.212), (-0.091 ± 0.142) and (0.067 ± 0.198)D in the FS-LASIK group (Z=-4.328, -3.197, both at P 0.05). Negative correlations were found between safety index or efficacy index and preoperative kappa angle in the SMILE group (r=-0.258, -0.257, both at P<0.05). Conclusions Both SMILE and FS-LASIK surgeries are effective and safe in correcting myopic astigmatism with good postoperative visual acuity.SMILE surgery shows less axis rotation and higher accuracy than FS-LASIK because of small incision and flapless procedure.The correction of cylinder can adjust based on experience of surgeon. Key words: Cornea/surgery; Femtosecond laser; Myopia; Astigmatism; Vector analysis; Small incision lenticule extraction

Comparison of Corneal Biological Healing After Femtosecond LASIK and Small Incision Lenticule Extraction Procedure

ABSTRACTPurpose: To assess and compare the dry-eye-associated parameters and corneal biomechanical status after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK).Methods: Sixty-five patients’ (128 eyes) were collected between November 2012 and April 2013. Thirty-five (69 eyes) underwent SMILE and thirty (59 eyes) underwent FS-LASIK. Visual acuity, manifest refraction, tear break-up time (TBUT), Schirmer’s test (ST), corneal sensitivity, Ocular Surface Disease Index (OSDI), corneal hysteresis (CH) and corneal resistance factor (CRF) were evaluated preoperatively and 1 day, 1 week, 1 month, 3 and 6 months postoperatively.Results: There was no significant difference in visual outcomes of SMILE and FS-LASIK (p = 0.208). TBUT, ST, CH and CRF decreased significantly after surgery in both groups (all p < 0.05); however, the decrease of TBUT, ST and CRF in the SMILE group was not as significant as that in the FS-LASIK group (all p < 0.05) and the change of CH value was comparable in both groups (p = 0.052).Corneal sensitivity was significantly decreased in the FS-LASIK group postoperatively (p < 0.05), but not significantly changed in the SMILE group (p > 0.05). OSDI scores were significantly increased after surgery for the two groups (all p < 0.05), and the scores were much higher in the FS-LASIK group than in the SMILE group (p = 0.000).Conclusion: The corneal biological healing of SMILE surgery was superior to FS-LASIK in the early period.

Early changes in ocular surface and tear inflammatory mediators after small-incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis.

PurposeTo characterize the early ocular-surface changes or tear inflammatory-mediators levels following small-incision lenticule extraction (ReLEx smile) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).MethodsForty-seven myopic subjects were recruited for this prospective study. Fifteen underwent ReLEx smile and thirty-two underwent FS-LASIK. Corneal fluorescein (FL) staining, tear break-up time (TBUT), Schirmer I test (SIT), ocular surface disease index (OSDI) and central corneal sensitivity were evaluated in all participants. Tears were collected and analyzed for interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nerve growth factor (NGF) and intercellular adhesion molecule-1 (ICAM-1) levels using multiplex magnetic beads. All measurements were preformed preoperatively and 1 day, 1 week, 1 month and 3 months postoperatively.ResultsFL scores in ReLEx smile group were lower than those of FS-LASIK group 1 week postoperatively (P = 0.010). Compared to the FS-LASIK group, longer TBUT were observed in ReLEx smile group 1 month (P = 0.029) and 3 months (P = 0.045) postoperatively. No significant differences were found in tear secretion for the two groups (P>0.05). OSDI scores were higher in FS-LASIK group 1 month after surgery (P = 0.020). Higher central corneal sensitivity was observed in ReLEx smile group 1 week, 1 month and 3 months (P<0.05) postoperatively. Compared to FS-LASIK group, lower and faster recovery of IL-6 and NGF levels in tears was observed in ReLEx smile group postoperatively (P<0.05). Tears TNF-α and ICAM-1 concentrations were not significantly different between the two groups at any follow-up time (P>0.05). Moreover, IL-6 and NGF levels correlated with ocular surface changes after ReLEx smile or FS-LASIK.ConclusionsIn the early postoperative period, ReLEx smile results in milder ocular surface changes than FS-LASIK. Furthermore, the tear inflammatory mediators IL-6 and NGF may play a crucial role in the ocular surface healing process following ReLEx smile and FS-LASIK.