Myopic Small Incision Lenticule Extraction Research Articles

VISUAL AND REFRACTIVE OUTCOME OF NEW GENERATION SMALL INCISION LENTICULE EXTRACTION (SMILE) IN MYOPIA AND MYOPIC ASTIGMATISM

Introduction: Two main options for the surgical correction of high myopia and myopic astigmatism are corneal refractive surgery and implantation of phakic intraocular lens (IOL). Small Incision Lenticule Extraction (SMILE) is becoming more popular technique which includes a minimally invasive flap-free procedure. The aim of this study is to evaluate the visual and refractive outcome of New Generation SMILE in myopia and myopic astigmatism. Methods: This is an observational retrospective study in patients who underwent SMILE using Visumax 800 Femtosecond laser procedure at Undaan Eye Hospital in period December 2022 to February 2023. Pre and post operative uncorrected visual acuity (UCVA), spherical equivalent (SE), astigmatism value, keratometry and intra ocular pressure (IOP) were evaluated at 1 day, 1 week and 1 month follow-up. Results: The study comprised 30 eyes of 15 patients age from 18 to 32 years old. The mean post operative UCVA was significantly improved to 0.03 ± 0.06 logMAR at 1-day, 0.02 ± 0.04 logMAR at 1-week and -0.01 ± 0.02 logMAR at 1-month follow-up compared to preoperative UCVA 1.35 ± 0.23 logMAR (p<0.001). The mean refractive spherical equivalent was significantly changed from -4.60 ± 1.47 D preoperatively to -0.57 ± 0.38 D at 1-month follow up (p < 0.001). The mean refractive astigmatism decreased from -1.02 ± 0.66 D preoperatively to -0.34 ± 0.25 D at 1- month follow up (p<0.001). Conclusion: New Generation of SMILE has shown good visual and refractive outcome for the correction of myopia and myopic astigmatic eyes since the early phase after surgery.

Impact of corrected refractive power on the corneal denervation and ocular surface in small-incision lenticule extraction and LASIK.

To evaluate the impact of corrected refractive power on the corneal denervation and ocular surface in small-incision lenticule extraction (SMILE) and laser in situ keratomileusis (LASIK). Singapore National Eye Center, Singapore. Prospective study. 88 eyes undergoing SMILE or LASIK were divided into low-moderate (manifest refractive spherical equivalent [MRSE] <-6.0 diopters [D]) and high myopic (MRSE ≥-6.0 D) groups. In vivo confocal microscopy and clinical assessments were performed preoperatively and at 1 month, 3 months, 6 months, and 12 months postoperatively. In SMILE, high myopic treatment presented with significantly greater reduction in the corneal nerve fiber area (CNFA) and nerve fiber fractal dimension (CFracDim) compared with low-moderate myopic treatment (both P < .05). There was a significant and negative correlation between the corrected MRSE and the reduction in corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length, CNFA, and CFracDim after SMILE (r = -0.38 to -0.66, all P < .05). In LASIK, a significant correlation between the MRSE and the changes in CNBD, corneal nerve fiber total branch density, CNFA (r = -0.37 to -0.41), and corneal nerve fiber width (r = 0.43) was observed (all P < .05). Compared with SMILE, LASIK had greater reduction in CNBD and CNFA for every diopter increase in the corrected MRSE. High myopic SMILE, compared with low-moderate myopic SMILE, resulted in significantly lower tear break-up time at 1 and 6 months (both P < .05). The changes in CNFA and CFracDim were significantly associated with Schirmer test values (both P < .001). Postoperative corneal denervation was related to corrected refractive power in both SMILE and LASIK. With the same refractive correction, LASIK led to more prominent corneal denervation.

Comparison of corneal power assessment methods after small incision lenticule extraction

Objective: To compare the accuracy of different corneal curvature parameters in assessing the corneal refractive status and tracking corneal power changes after small incision lenticule extraction (SMILE). Methods: This prospective cross-sectional study tracked and recorded total corneal curvature parameters measured by different instruments before and three months after SMILE for myopia. These parameters, including total keratometry (TK) from the IOLMaster 700, total corneal refractive power (TCRP) from the Pentacam AXL, real keratometry (RK) from the CASIA 2, and corrected parameters calculated using the Haigis, Shammas, and Maloney methods, were compared with data obtained using the clinical history method (CHM). Surgically induced changes in TK, TCRP, and RK were analyzed and compared with those in spherical equivalent on the corneal plane (ΔSEco). Results: The study included 40 eyes (40 participants). After SMILE, the difference was smallest between TK [(0.08±0.38) D] and CHM values (P>0.05). However, TCRP, RK, KHaigis, KShammas, and KMaloney were significantly different from CHM data (P<0.05). The width of the 95% limits of agreement of TK (1.49 D) was narrowest, followed by that of RK (1.57 D). Pearson analysis showed that each parameter had a good correlation with CHM data. The differences between the changes in TK, TCRP and RK caused by surgery and ΔSEco were (0.03±0.39) D, (0.17±0.43) D, and (-0.19±0.46) D, respectively. The width of the 95% limits of agreement of ΔTK (1.54 D) was narrowest, and the correlation coefficient of ΔTK (0.951) was highest. Conclusion: The parameter TK of the IOLMaster 700 can provide accurate and objective corneal power evaluation after SMILE.

Transient Light Sensitivity Syndrome (TLSS) Incidence Following Femtosecond LASIK for Myopic and Hyperopic Eyes and Femtosecond SMILE for Myopic Eyes.

To evaluate and compare the incidence of transient light sensitivity syndrome (TLSS) after myopic laser in situ keratomileusis (LASIK), hyperopic LASIK, and myopic small incision lenticule extraction (SMILE). A retrospective analysis was performed of consecutive LASIK and myopic SMILE cases, performed with the VisuMax femtosecond laser and MEL 80 or MEL 90 excimer laser (both Carl Zeiss Meditec AG) between January 2010 and February 2021 at London Vision Clinic, London, United Kingdom. A chart review was performed to find cases of clinically significant TLSS, identified as patients prescribed anti-inflammatory medications between 2 weeks and 6 months after surgery to manage photophobia. The incidence of TLSS was calculated for three groups: myopic SMILE, myopic LASIK, and hyperopic LASIK. The incidence of TLSS was then calculated for three subgroups within each treatment type based on spherical equivalent refraction treated. For myopic SMILE and myopic LASIK, it was 0.00 to -4.00 diopters (D) (low), -4.01 to -8.00 D (moderate), and -8.01 to -14.00 D (high). For hyperopic LASIK, it was 0.00 to +2.00 D (low), +2.01 to +4.00 D (moderate), and +4.01 to +6.50 D (high). The range of treatment for myopia was similar between the LASIK and SMILE groups. The incidence of TLSS was 1.2% for the myopic SMILE group, 5.3% for the myopic LASIK group, and 9.0% for the hyperopic LASIK group. The difference was statistically significant between all groups (P < .001). For myopic SMILE, the incidence of TLSS was independent of spherical equivalent refraction for low (1.4%), moderate (1.0%), and high (1.1%) myopia (P > .05). Similarly, for hyperopic LASIK, the incidence was similar for low (9.4%), moderate (8.7%), and high (8.7%) hyperopia (P > .05). In contrast, for myopic LASIK, the incidence of TLSS was "dose-dependent" on refractive error treated, with an incidence of 4.7% for low, 5.8% for moderate, and 8.1% for high myopia (P < .001). The incidence of TLSS was higher after myopic LASIK than after myopic SMILE, higher after hyperopic than myopic LASIK, and "dose-dependent" for myopic LASIK but did not vary by correction in myopic SMILE. This is the first report describing the phenomenon of late TLSS occurring between 8 weeks and 6 months after surgery, [J Refract Surg. 2023:39(6):366-373.].

Influencing Factors of Glare in Patients With Myopia After Small Incision Lenticule Extraction.

To investigate influencing factors of glare in patients with myopia after small incision lenticule extraction (SMILE). Thirty patients (60 eyes) aged 24.9 ± 4.5 years with spherical equivalent of -6.69 ± 1.10 diopters (D) and astigmatism of -1.25 ± 0.76 D who underwent SMILE were consecutively recruited in this prospective study. Visual acuity, subjective refraction, Pentacam corneal topography (Oculus Optikgeräte GmbH), pupillometry, and glare test (Monpack One; Metrovision) were measured preoperatively and postoperatively. All patients were followed up for 6 months. The generalized estimation equation was used to judge the determinants of glare after SMILE, and a P value less than .05 was statistically significant. Under mesopic conditions, the halo radii preoperatively and at 1, 3, and 6 months after SMILE were 207.72 ± 46.67, 216.17 ± 40.63, 200.67 ± 34.68, and 193.50 ± 40.75 minutes of arc (arcmin), respectively. Under photopic conditions, the glare radii were 79.10 ± 17.78, 87.00 ± 20.44, 78.00 ± 14.59, and 72.00 ± 15.27 arcmin, respectively. Compared with preoperative glare, no significant changes were detected in postoperative glare. However, glare at 6 months was statistically significantly improved compared to the values at 1 month (both P < .05). Under mesopic conditions, the main influencing factors of glare were sphere (P = .007), astigmatism (P = .032), uncorrected distance visual acuity (UDVA) (P < .001), and postoperative time (all P < .05). Under photopic conditions, the main influencing factors of glare were astigmatism, UDVA, and postoperative time (all P < .05). Glare improved with time during the early stages after SMILE for myopia. Less glare was found to be associated with better UDVA, and greater residual astigmatism and sphere translated to more obvious glare. [J Refract Surg. 2023;39(6):398-404.].

Postoperative efficacy, safety, predictability, and visual quality of implantable collamer lens implantation versus small incision lenticule extraction in myopic eyes: a Meta-analysis.

To compare the postoperative efficacy, safety, predictability, and visual quality of implantable collamer lens (ICL) implantation versus small incision lenticule extraction (SMILE) in myopia eyes. PubMed, EMBASE, Web of Science, Cochrane Library and several Chinese databases were searched at May 2021 to select relevant studies in comparison of clinical outcomes between ICL implantation and SMILE for myopia. The primary outcomes were efficacy, safety, and predictability. And the secondary outcomes were postoperative higher-order ocular aberrations (HOAs), modulation transfer function cutoff frequency (MTF), objective scatter index (OSI), contrast sensitivity and a quality of vision (QoV) questionnaire. A total of 1036 eyes from 10 studies, of which 503 eyes underwent ICL implantation and 533 eyes underwent SMILE, were enrolled in this Meta-analysis. Pooled results revealed that ICL group had a better safety index and post-corrected distance visual acuity (CDVA) (P=0.007, <0.00001, respectively), and a lower percentage of eyes with a postoperative CDVA lost 1 line (P=0.007) than the SMILE group. No significant differences were found in comparison of the other primary outcomes. In the long-term follow-up (>6mo), ICL group had a lower total HOA, coma, and spherical aberration than SMILE group (P=0.003, <0.00001, 0.04). Yet higher trefoil was found in ICL group at 6mo after surgery (P=0.003). Additionally, ICL group also had a higher MTF value (P=0.02), and a higher contrast sensitivity score for spatial frequencies of 1.5, 6, and 12 cpds (P=0.02, 0.005, 0.02, respectively). And it also had a lower score of bothersome in QoV questionnaire than SMILE group (P=0.003). ICL implantation and SMILE have similar and comparable outcomes in term of the efficacy and predictability for correcting high myopia. However, ICL group is relatively safer and also has better visual quality in comparison of SMILE group.

Anterior segment inflammation and its association with dry eye parameters following myopic SMILE and FS-LASIK

Purpose To evaluate dry eye and anterior segment inflammation after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and investigate their association. Methods This prospective and observational study included 96 eyes from 48 myopic patients. The evaluation was performed at baseline, postoperative day 1, week 1, month 1 and month 3. Outcome measures included anterior chamber flare, bulbar redness (BR), limbal redness (LR), ocular surface disease index (OSDI), tear meniscus height (TMH), the first and average noninvasive breakup time (NIBUT-1, NIBUT-a), fluorescein breakup time (FBUT), corneal fluorescein staining (CFS), and Schirmer I. Generalized estimating equations (GEEs) were applied to explore the correlation between flare and ocular surface parameters. Results Flare increased significantly in both groups at day 1 and week 1 and then returned to baseline at month 1. In both groups, BR decreased on day 1 and then gradually increased towards the baseline. In FS-LASIK, LR was lower than baseline at day 1 and month 3. An increase in OSDI was found in the SMILE group on day 1, and in the FS-LASIK group at day 1 to month 1. NIBUT-1 and NIBUT-a decreased significantly on day 1 in both groups. At month 3, NIBUT-a did not return to baseline in FS-LASIK. CFS increased significantly at week 1 in both groups. All parameters were comparable between SMILE and FS-LASIK except for OSDI and NIBUT-a. Time and spherical equivalent showed a correlation with flare. Conclusions Both SMILE and FS-LASIK induced elevated anterior chamber flare and dry eye. However, flare might not be considered a factor determining perioperative dry eye. Key Messages Dry eye disease is common after corneal refractive surgery. Signs and symptoms of dry eye disease persist longer after FS-LASIK compared with SMILE. Both FS-LASIK and SMILE transiently disrupted blood-aqueous barrier integrity, leading to anterior segment inflammation. Anterior chamber flare might not be considered a factor explaining perioperative dry eye, other biomarkers remain for future exploration.

Evaluating early-stage disk halo changes after small incision lenticule extraction.

To investigate early changes in the disk halo under different light conditions after myopic small incision lenticule extraction (SMILE). This prospective study included 70 eyes of 70 myopic patients aged 18-33 years, with a spherical equivalent (SE) of -5.87 ± 1.86 D, who underwent SMILE. The subjective refraction, higher-order aberrations (HOAs), pupillometry, and halo were measured preoperatively and postoperatively to analyse disk halo variations and correlated factors. At 5 cd/m2 and 1 cd/m2 luminance, the halo radius in the high myopia (HM) group reached a postoperative peak after 1 week (p = 0.000 and 0.019, respectively), and recovered to baseline after 3 months. In the low-to-moderate (LM) myopia group, the halo radius did not differ 1 week postoperatively compared to the preoperative level (p = 0.015), but significantly improved after 3 months (p = 0.000). The halo radius correlated with SE, uncorrected distance visual acuity (UDVA), ocular HOAs, coma, and the pupillary light reflex in the LM group at all time points, but there were no correlations in the HM group. Halo symptoms occurred early after SMILE, but recovered within 3 months. The recovery process was slower in the HM group than in the LM group, and the halo radius correlated with SE, UDVA, ocular HOAs, coma, and the pupillary light reflex.

Changes in Light Disturbance Analyzer Evaluation in SMILE for High Myopia and Astigmatism.

To study the objective change in light disturbance around a glare source using the Light Disturbance Analyzer (LDA) (Binarytarget Lda) and correlate this with the validated subjective quality of vision (QoV) questionnaire in small incision lenticule extraction (SMILE) for high compound myopic astigmatism. This was a prospective study recruiting 114 patients undergoing SMILE with attempted spherical equivalent refraction (SEQ) correction from -9.00 to -13.00 diopters (D), and cylinder up to 5.00 D. The LDA was used before and 3 and 12 months after surgery to evaluate the Light Disturbance Area, Light Disturbance Index, Best Fit Circle Radius, and Best Fit Circle Irregularity. Patients completed the Rasch-validated QoV questionnaire before and 12 months after surgery. Correlation analysis was performed between the LDA parameters and the QoV frequency, severity, and bothersomeness for halos and starbursts. At 12 months, there was a non-statistically signifcant change of 11.9% for Light Disturbance Area and Light Disturbance Index and 6.5% for Best Fit Circle Radius. There was an increase of 81.9% for Best Fit Circle Irregularity (P = .017). Light Disturbance Area, Light Disturbance Index, and Best Fit Circle Radius correlated with bothersomeness for QoV halos, and with frequency, severity and bothersomeness for QoV star-bursts (P < .05), albeit with a low correlation coefficient (R2 < 0.13). There was no correlation between increase in Best Fit Circle Irregularity and the halo and starburst scores from the QoV questionnaire. LDA Best Fit Circle Irregularity was found to increase following high myopic SMILE. Other LDA parameters appeared to increase, but a much larger sample would be required to find statistical significance. The change in LDA parameters was only weakly correlated with QoV halo and starburst metrics, representing the wide variation in inter-subject perception. [J Refract Surg. 2022;38(11):725-732.].

Comparison of Corneal Higher-Order Aberrations Following Topography-Guided LASIK and SMILE for Myopic Correction: A Propensity Score Matching Analysis.

Ocular aberrations, particularly corneal higher-order aberrations (HOAs), which impair visual quality, should be minimized or corrected during any laser vision correction. We compared changes in visual outcomes, including HOAs, in patients who underwent Topography-Guided laser-assisted in situ keratomileusis (TG-LASIK) or small-incision lenticule extraction (SMILE) after propensity score matching (PSM) to reduce selection bias. Of 2749 patients who underwent SMILE or TG-LASIK for myopia, 152 eyes underwent complete ophthalmic examination preoperatively and over six months postoperatively. Visual outcomes were comparatively analyzed after PSM. As a result, 45 eyes were included in each group after PSM. There was a comparable improvement in visual acuity (VA) and refractive parameters postoperatively, with no difference between the two PSM-groups. However, 6.6% in the SMILE PSM-group lost two or more lines of Snellen VA at the six-month follow-up, while none in the TG-LASIK PSM-group did. Specifically, the SMILE PSM-group showed a significant increase in corneal HOAs, including spherical aberration, coma, and total HOAs (0.0736 ± 0.162 μm; 0.181 ± 0.233 μm; and 0.151 ± 0.178 μm, respectively), whereas TG-LASIK PSM-group did not. Furthermore, SMILE PSM-group had greater postoperative corneal HOAs than those in TG-LASIK PSM-group. Collectively, TG-LASIK induces fewer corneal HOAs even after facilitating between-group comparability using PSM analysis. TG-LASIK provides better visual quality than SMILE for myopia.

Objective and Subjective Quality of Vision After SMILE for High Myopia and Astigmatism.

To report subjective and objective quality of vision (QoV) results for high myopic small incision lenticule extraction (SMILE) between -9.00 and -13.00 diopters (D). This was a prospective study recruiting 114 patients undergoing SMILE with attempted spherical equivalent refraction (SEQ) correction from -9.00 to -13.00 D, and cylinder up to 5.00 D. Patients were informed before surgery of the increased risk of QoV symptoms. Patients completed the Rasch validated QoV questionnaire. Objective QoV was assessed by corneal and whole eye aberrations, HD Analyzer Objective Scatter Index (OSI) (Keeler), and contrast sensitivity. Patient satisfaction was assessed on a scale from 0 (very dissatisfied) to 10 (very satisfied). Individual item and total Rasch-scaled scores for the three subscales (frequency, severity, and bothersomeness) of the QoV questionnaire were calculated before and 12 months after surgery. The mean patient satisfaction score was 9.27 ± 1.18 (range: 2 to 10), 8 or higher in 93%, and 7 or higher in 98% of patients. One patient with a satisfaction score of 2 had a simple refractive error re-treatment and then reported a satisfaction score of 10. The total mean ± standard deviation Rasch-scaled QoV score for the frequency, severity, and bothersomeness subscales before surgery was 24 ± 19, 20 ± 16, and 19 ± 18, respectively. Scores increased after surgery to 41 ± 18, 32 ± 16, and 30 ± 21, respectively (P < .001). Corneal aberrations (6 mm, OSI) increased on average by 0.39 µm for spherical aberration, 0.41 µm for coma, and 0.56 µm for higher order aberrations root mean square. OSI increased on average by 0.58. There was a small but statistically significant improvement in contrast sensitivity at 3, 6, 12, and 18 cycles per degree. There were no statistically significant correlations found between subjective scores for starbursts and objective measurements. Satisfaction was high following SMILE for high myopia. As expected, there was an increase in QoV symptoms, mainly glare and starbursts. The acceptance of QoV symptoms for high myopic SMILE was high, indicating that residual refractive error and visual acuity are the major drivers for patient satisfaction with appropriate preoperative informed consent. [J Refract Surg. 2022;38(7):404-413.].

Evaluation of Wide Corneal Epithelial Remodeling after Small Incision Lenticule Extraction (SMILE) with Wide-Field Optical Coherence Tomography.

Purpose This study aims to assess the corneal epithelial remodeling within a 9 mm diameter zone induced by small incision lenticule extraction (SMILE) and evaluate its relationship with the refractive outcomes. Methods A total of 64 eyes of 64 patients were included. Wide-field optical coherence tomography (OCT) was used to measure the epithelial thickness (ET) across a 9 mm diameter area, preoperatively, and after one day, one week, one month, three months, and six months postoperatively. The ET changes were compared among the different time points and analyzed zones. Results The ET increases from one week to three months and stabilized from three months to six months. Compared to the preoperative values, the mean ET changes at six months in central (2 mm), paracentral (2–5 mm), mid-peripheral (5–7 mm), and peripheral (7–9 mm) zones were 4.37, 4.36, 1.61, and −1.59 μm, respectively. The correlation between the epithelial thickening and the amount of myopia correction was positive in central (P = 0.001) and paracentral zones (P < 0.001) and negative in peripheral zone (P = 0.006). The intended diameter of the optical zone was negatively related to epithelial hyperplasia in the central (P = 0.020) and paracentral zone (P = 0.006), and the correlation was positive in the mid-peripheral zone (P = 0.001). The epithelial thickening of central zone (P = 0.012) and the difference of mean ET between central and paracentral zone (P = 0.020) were negatively related to the spherical equivalent at six months. Conclusion An asymmetric lenticule-like pattern of epithelial remodeling occurred in 9 mm diameter cornea at six months after myopic SMILE. The epithelial remodeling may affect the refractive outcomes of SMILE.

Toric Lenticule Implantation for Correction of Hyperopia and Astigmatism Following Small Incision Lenticule Intrastromal Keratoplasty With the Triple Marking Method.

To describe the first use of toric lenticule implantation with the triple marking method to correct hyperopia and hyperopic astigmatism following small incision lenticule intrastromal keratoplasty (SMI-LIKE). Five eyes of four patients with hyperopia (+5.25 to +9.50 diopters sphere) were included. Allogenic toric lenticules extracted using myopic small incision lenticule extraction were implanted and rotated into a femtosecond laser-created stromal pocket in hyperopic recipients with triple marking. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction, corneal topography, and Fourier-domain optical coherence tomography images were examined 6 months postoperatively. Six months after surgery, 4 eyes (80%) gained two or more lines of UDVA, and 1 eye (20%) had unchanged UDVA. No eyes lost any lines of CDVA. The spherical equivalent decreased from +6.23 ± 1.34 diopters (D) preoperatively to -0.35 ± 0.27 D postoperatively. The mean refractive astigmatism also decreased significantly from -2.15 ± 1.10 D preoperatively to -0.70 ± 0.21 D postoperatively. Of 5 treated eyes, 2 (40%) had postoperative astigmatism within ±0.50 diopters cylinder and 5 (100%) within ±1.00 diopters cylinder. Corneal topography showed a significant increase in the anterior surface keratometry value, whereas corneal astigmatism decreased from 2.62 ± 1.55 to 1.10 ± 0.44 D. Vector analyses suggested good predictability and efficacy for astigmatism correction. Implantation of toric lenticules following SMI-LIKE with the triple marking method is a feasible alternative for correcting hyperopia and hyperopic astigmatism, and the short-term results seem safe and stable. [J Refract Surg. 2022;38(2):82-88.].

Effect of preoperative keratometry on visual outcomes after small-incision lenticule extraction for myopia

PurposeTo investigate the relationship between preoperative keratometry (K) and postoperative refraction and compare the visual outcomes after small-incision lenticule extraction (SMILE) between preoperative flat and steep corneas.MethodsThis study involved 814 consecutive eyes of 409 patients who underwent SMILE. A month later, a linear regression analysis of the relationship between preoperative K and the residual spherical equivalent (SE) along with eyes divided by a single standard deviation between flat and steep corneas (< 41.85 D, > 44.57 D, respectively) was conducted. Eyes were distinguished based on the degree of myopia.ResultsOne month after surgery, no significant correlation existed between mean preoperative K and residual SE (P = 0.459). Linear regression analysis showed a weak negative correlation between flat corneas (r2 = 0.042, P = 0.025) rather than steep corneas (P = 0.908). Eyes with preoperative low myopia (< 3.00 D) (r2 = 0.233, P = 0.001) had a weak correlation compared with moderate and high myopia (P = 0.272, P = 0.257, respectively). Twelve months later, the predictability, safety, and efficacy did not vary between preoperative flat and steep corneas (P > 0.05).ConclusionsOne month after SMILE for myopia, the corneas were flatter in the preoperative flat corneas or all the low myopic corneas, and they were more overcorrected. However, preoperative corneal curvature does not influence visual outcomes at 1 year after SMILE.

Prophylactic corneal crosslinking in myopic small-incision lenticule extraction - Long-term visual and refractive outcomes.

Purpose:To analyze the efficacy, safety, predictability, and stability in myopic and astigmatic small-incision lenticule extraction (SMILE) with simultaneous prophylactic corneal crosslinking (CXL) in thin corneas.Methods:A total of 48 eyes from 24 patients who underwent myopic and astigmatism SMILE with simultaneous prophylactic CXL were included in this retrospective study. All patients had a 24-month follow-up. A femtosecond laser was performed with VisuMax (Carl Zeiss Meditec). CXL treatment was applied when the predicted stromal thickness was less than 330 μm.Results:The patients’ mean age was 31.58 ± 6.23 years. The previous mean spherical equivalent was − 6.85 ± 1.80 (−9.75 to − 2.00) D. The postoperative mean spherical equivalent was − 0.50 ± 0.26 (−1.00 to + 0.25) D; 60% of the eyes had 20/20 or better; 19% lost one line; 58% were within ± 0.50 D; and 8.3% of the eyes changed 0.50 D or more between 3 and 24 months.Conclusion:Prophylactic CXL with simultaneous SMILE for myopia and astigmatism femtosecond laser surgery technique appears to be partially effective, safe, predictable, and stable after 24 months of follow-up.

Visual Outcomes After Implantation of Allogenic Lenticule in a 100-µm Pocket for Moderate to High Hyperopia: 2-Year Results.

To investigate 2-year visual outcomes, stability, and predictability after allogenic lenticule implantation in a 100-µm pocket for moderate to high hyperopia correction. In this prospective case series, 14 eyes of 9 patients with moderate to high hyperopia ranging from +3.00 to +8.00 diopters sphere were included between March and September 2018. Allogenic lenticules extracted from myopic small incision lenticule extraction were implanted into a pocket created by femtosecond laser at a 100-µm depth in recipients with hyperopia. All patients were followed up for 2 years. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, corneal topography, Fourier-domain optical coherence tomography, and in vivo confocal microscopy were examined. At postoperative 2 years, 2 eyes (14.3%) gained one line of CDVA, 11 eyes (78.6%) had unchanged CDVA, and 1 eye (7.1%) lost one line of CDVA. No eyes lost two or more lines of CDVA. Twelve of the treated eyes (85.7%) had postoperative uncorrected near visual acuity equal to or better than pre-operative values. The spherical equivalent decreased from +5.53 ± 1.45 D preoperatively to -0.60 ± 1.20 D at postoperative year 2 (P < .001). The anterior mean keratometric readings increased from 42.41 ± 1.03 D preoperatively to 48.38 ± 1.98 D at postoperative year 2 (P < .001). Of 14 treated eyes, 10 eyes (71.4%) had spherical equivalent within ±1.00 D. The findings suggest that allogenic lenticule transplantation may be a promising option for the correction of moderate to high hyperopia. [J Refract Surg. 2021;37(11):734-740.].

Impact of extreme (flat and steep) keratometry on the safety and efficacy of small incision lenticule extraction (SMILE)

Little is known about the connection between preoperative keratometry and postoperative results of myopic small-incision lenticule extraction (SMILE). To determine the influence of extreme (flat and steep) corneal keratometry on the safety and efficacy of SMILE, the databases of the Department of Ophthalmology, Ludwig-Maximilians-University Munich, Germany, and SMILE Eyes Linz, Austria, were screened for patients with steep and flat keratometry who had undergone SMILE. In this cross-sectional matched comparative cohort study, eyes with markedly flat (< 42.0 diopters; D) or steep (≥ 47.0D) preoperative corneal keratometry were matched to a cohort of eyes with regular keratometry (42.0–46.9D) by preoperative manifest refractive spherical equivalent and cylinder, age, corrected distance visual acuity and surgical SMILE parameters. The standardized graphs and terms for refractive surgery results were applied to compare the three groups. Changes in higher order aberrations (HOAs) were evaluated on Scheimpflug imaging. In total, 63 eyes (21 each) of 54 patients with a mean refractive spherical equivalent of − 5.21 ± 1.59 D were followed up for a mean of 9.2 ± 6.1 (minimum ≥ 3) months. Mean baseline keratometry was 41.3 ± 0.7D (flat), 45.5 ± 1.0D (regular) and 47.7 ± 0.6D (steep) (p < 0.0001). Compared to the regular group, the flat and the steep cornea group resulted in a non-inferior percentage of eyes within ± 0.50 D of target refraction (p = 0.20), uncorrected distance visual acuity (p = 0.95) and corrected distance visual acuity (p = 0.20). Flat corneas however experienced a stronger induction of spherical aberration (SA) compared to the steep group (p = 0.0005). In conclusion, non-inferior outcomes of SMILE can also be expected in eyes with steep (≥ 47D) or flat (< 42D) preoperative keratometry, while SMILE however induces more SA in eyes with a flat keratometry.

Corneal Remodeling After Myopic SMILE Versus FS-LASIK: A Spatial Analysis of Short- and Mid-Term Corneal Thickness, Volume, and Shape Changes.

To evaluate the short- and mid-term changes of corneal thickness spatial profile (CTSP), corneal volume distribution (CVD), and corneal asphericity after small-incision lenticule extraction (SMILE) for correction of myopia and astigmatism and compare the results with femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Thirty eyes of 18 patients who underwent SMILE were compared with a group of 30 eyes of 16 patients who underwent FS-LASIK. The groups were matched for preoperative central corneal thickness and lenticule thickness/ablation depth. Scheimpflug corneal tomography was performed preoperatively and postoperatively at 2 months and 3 years. The CTSP was evaluated on 4 concentric rings (2, 4, 6, and 8 mm). The CVD was evaluated at 3 concentric zones (3, 5, and 7 mm). Changes in the anterior and posterior asphericity at a 6-mm zone were also evaluated. Between the 2-month and 3-year examination, the CTSP showed a similar increase for both groups at all measured points and rings ( P ≥ 0.168). The CVD also showed a similar increase for both groups at all measured zones ( P ≥ 0.278). The anterior corneal asphericity remained stable after SMILE (2-mo Q = 0.46 ± 0.27; 3-yr Q = 0.45 ± 0.27; P = 0.711) but decreased significantly after FS-LASIK (2-mo Q = 0.52 ± 0.47; 3-yr Q = 0.47 ± 0.44; P = 0.028). Similarly, the posterior corneal asphericity remained stable after SMILE (2-mo Q = -0.11 ± 0.15; 3-yr Q = -0.11 ± 0.13; P = 0.902) but decreased significantly after FS-LASIK (2-mo Q = -0.13 ± 0.14; 3-yr Q = -0.16 ± 0.15; P = 0.034). CTSP and CVD between the 2-month and 3-year examination showed a similar increase after SMILE and FS-LASIK. During the postoperative course, the anterior and posterior corneal asphericity remained more stable after SMILE compared with FS-LASIK.

Comparison of effective corneal refractive centration to the visual axis: LASIK vs SMILE, a contralateral eye digitized comparison of the postoperative result.

To define and compare the centration of the ablation effect in laser in situ keratomileusis (LASIK) with the corresponding effect in small-incision lenticule extraction (SMILE), in myopic laser vision correction to possibly explain the refractive performance differences noted between the two procedures in a contralateral eye study. Private ambulatory eye surgery unit. Prospective randomized contralateral eye study. In 22 consecutive patients (44 eyes), 1 eye was prospectively randomized to undergo myopic topography-guided LASIK treatment and the contralateral eye to undergo SMILE; digital image analysis of the achieved centration to the aimed corneal vertex was assessed for both procedures on perioperative Scheimpflug tangential curvature maps, using a proprietary digitized methodology. The radial displacement measured in micrometers in the above treated 44 eyes, between the attempted centration point on the corneal vertex vs the center of the measured effective anterior corneal curvature flattening was on average 130 ± 62 mm in the 22 eyes of LASIK group and 313 ± 144 mm in the 22 contralateral eyes of the SMILE group (P < .001). In this contralateral eye study, topography-guided myopic LASIK was found to achieve significantly better effective centration compared with myopic SMILE, in regard to digitally measured decentration of the effective refractive change achieved in the anterior corneal curvature from the corneal vertex. This may explain the previously reported superior visual outcomes in the LASIK group eyes when compared with the contralateral SMILE group eyes.

Corneal Epithelial Thickness Changes Following SMILE for Myopia With High Astigmatism.

To evaluate the corneal epithelial thickness (CET) profile changes after small incision lenticule extraction (SMILE) surgery for myopic astigmatism correction of greater than 2.00 diopters (D). This prospective observational study included 40 eyes (23 patients) treated with SMILE for myopia with cylinders of -2.25 to -4.50 D. Along with standard ophthalmic examinations, CET maps with a diameter of 9 mm were measured by high-resolution spectral-domain optical coherence tomography preoperatively and postoperatively. Correlations between the degree of residual astigmatism and the difference in CET values between preoperative flat and steep meridians were analyzed. The CET showed significant changes in the central (2 mm), paracentral (2 to 5 mm), midperipheral (5 to 7 mm), and peripheral (7 to 9 mm) zones 6 months after SMILE (P < .001). Among the regions, the CET in the paracentral zones displayed the largest increase (9.75%) with the highest average thickness (57.29 µm). Moreover, symmetrical regional epithelial thickening at the preoperative astigmatism axis was observed in the midperipheral zones. The difference in CET between preoperative flat and steep meridians in the mid-peripheral zones continuously increased from postoperative 1 day to 6 months. This difference was positively correlated with the residual cylinder errors at 6 months postoperatively (r = -0.334, P = .035). The 9-mm diameter CET in eyes with high astigmatism significantly increased 6 months after SMILE. Additionally, the difference in CET between preoperative flat and steep meridians in midperipheral zones may be related to astigmatic undercorrection in SMILE. [J Refract Surg. 2021;37(4):224-230.].