Long-term visual quality after small incision lenticule extraction (SMILE) and laser assisted subepithelial keratomileusis (LASEK) for low myopia.

BACKGROUND: Few studies have reported the visual outcomes of small-incision lenticule extraction (SMILE) and laser-assisted subepithelial keratomileusis (LASEK) for myopia correction. This study aims to compare the visual quality and corneal wavefront aberrations after SMILE and LASEK for low-myopia correction. METHODS: In this prospective study, we included 29 eyes of 29 patients who received SMILE and 23 eyes of 23 patients who received LASEK between June 2018 and January 2019. The following measurements were assessed: uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, corneal wavefront aberrations, and subjective visual quality. All patients were followed up for two years. RESULTS: All procedures were uneventful. An efficacy index of 1.19 ± 0.17 was established in the SMILE group and 1.23 ± 0.20 in the LASEK group. No eyes lost more than two lines of CDVA. We found that 93% (27/29) of the treated eyes in the SMILE group and 91% (21/23) in the LASEK group had spherical equivalent (SE) within ± 0.25D. The increases in the total corneal spherical aberration and the corneal front spherical aberration were lower in the SMILE group than in the LASEK group (P < 0.01). In contrast, the increases in the total corneal vertical coma and the corneal front vertical coma in the SMILE group were greater than those in the LASEK group (P < 0.01). CONCLUSION: Both SMILE and LASEK have good safety, stability, and patient-reported satisfaction for low myopia. SMILE induced less corneal spherical aberration but greater vertical coma than LASEK.

Laser-based refractive surgery techniques to treat myopia in adults. An overview of systematic reviews and meta-analyses.

Systematic reviews (SRs) and meta-analyses (MAs) are of great importance for basing clinical decisions. However, misleading interpretations may result when informed decisions rest on biased review papers with methodological issues. To evaluate which treatment is optimal, an overview was made of SRs and MAs to establish the quality and certainty of meta-evidence published on the efficacy of laser-based refractive surgery techniques for treating myopia in adults. A search was made in five databases and was updated using Really Simple Syndication (RSS) feed appliances up to April 2021; SRs with or without MAs were included. Methodological quality was appraised using the AMSTAR-2 tool. The best available reviews were summarized using the GRADE approach. The corrected covered area (CCA) was used to determine the degree of over-representation of publications. The risk of bias of the primary studies was disclosed visually. Thirty-six studies published between 2003 and 2021 were included. Twenty SRs (56%) were conducted in China. The most studied comparisons were SMILE versus FS-LASIK (19%) and FS-LASIK versus MM-LASIK (11%). Of the 251 overlapping index publications, 165 were unique (CCA = 0.015%), representing a negligible risk of skewed reporting. The AMSTAR-2 tool showed most SRs to have critically low or low quality. Nine reviews presented moderate quality. The GRADE approach of the 41 a priori outcomes evidenced critically low and low certainty of evidence. Only the spherical equivalent refraction changes at 12 months between LASEK and PRK showed moderate certainty of evidence, favouring PRK (mean difference 0.06, 95%CI [-0.02 to 0.14], I2 = 0%; p ≥ 0.05). Index trials among less biased reviews are prone to selection, performance and reporting bias. The appraised techniques exhibit comparable results in terms of efficacy. There is moderate certainty of evidence in favour of the use of PRK over LASEK in terms of the spherical equivalent refraction error changes at 1 year of follow-up. Most appraised SRs presented methodological flaws in critical domains, resulting in a low to critically low certainty of evidence after GRADE appraisal. Therefore, investigators need to study and compare the different laser-based refractive techniques to provide better evidence-based medicine. Further well-designed, high-quality clinical trials and SRs are needed to reappraise the current findings.

The Effectiveness of Corneal Epithelial Debridement Performed with an Alcohol-Impregnated Sponge.

OBJECTIVE: To evaluate the clinical outcomes of patients who underwent corneal surgery with debridement of epithelium by localised application of an alcohol-impregnated sponge instead of the usual alcohol reservoir method. DESIGN: This study retrospectively included 52 eyes of 27 patients who underwent LASEK (laser-assisted subepithelial keratectomy) and CXL (cross-linking) surgery after application of this alcohol-assisted debridement method between January 2019 and April 2019. PARTICIPANTS: Twenty-four patients who underwent LASEK and three patients who underwent CXL surgery were included in this study, which comprised a total of 52 eye operations. METHODS: Epithelial debridement was performed after placing a 20% ethanol-impregnated sponge on the cornea for 20 seconds. RESULTS: The mean pachymetry value was 509.40 ± 30.37 µm, the mean preoperative spherical equivalent was - 2.14 ± 1.02 dioptres, and the highest myopia and astigmatism values were - 4.25 dioptres and - 2.75 dioptres, respectively. It was seen that the corneal epithelium was completely and easily debrided in a size identical to that of the applied sponge. CONCLUSIONS: Complete debridement of the corneal epithelium can be performed quickly, safely, and easily with this specially prepared sponge.

Effect of Laser-assisted Subepithelial Keratectomy with Mitomycin C on Corneal Optical Density Measured with Confocal Microscopy.

SIGNIFICANCE: The development of confocal microscopy allows one to obtain high-resolution corneal images like its optical density. Some studies have evaluated the optical density with Scheimpflug cameras in the early post-operative period after photorefractive keratectomy, but no studies have evaluated the long-term evolution of optical density after surface ablation when mitomycin C is used. PURPOSE: This work aimed to study the changes in corneal optical density measured with confocal microscopy in eyes treated with laser-assisted subepithelial keratectomy (LASEK) and intraoperative mitomycin C (MMC) to correct myopia. METHODS: A study of 24 consecutive myopic eyes that underwent LASEK with 0.02% MMC and a control group of 24 healthy nontreated eyes was performed. Optical density was measured using the images by the confocal microscopy of the Heidelberg Retina Tomograph II with the Rostock Cornea Module. An analysis of confocal microscopy images was performed using the ImageJ software to obtain the optical density, in gray-scale units (GSU). The optical density of the stromal bed was evaluated 3 months, 15 months, and 3 years after surgery and was compared with the optical density at the equivalent depth of the stroma in controls. RESULTS: The mean values of optical density for the LASEK group were 81.7 ± 9.7, 78.6 ± 11.7, and 73.6 ± 18.7 GSU at 3 months, 15 months, and 3 years, respectively, and it was 61.8 ± 8.2 GSU for the control group. A statistically higher optical density 3 and 15 months after LASEK with MMC was found compared with controls (P < .001). No significant difference was found in optical density at 3 years post-operatively. CONCLUSIONS: Our study suggests that, after LASEK with MMC, the anterior corneal stroma has a higher optical density at 3 and 15 months post-operatively, which gradually returns to normal values 3 years after surgery.

Wavefront excimer laser refractive surgery for adults with refractive errors.

BACKGROUND: Refractive errors (conditions in which the eye fails to focus objects accurately on the retina due to defects in the refractive system), are the most common cause of visual impairment. Myopia, hyperopia, and astigmatism are low-order aberrations, usually corrected with spectacles, contact lenses, or conventional refractive surgery. Higher-order aberrations (HOAs) can be quantified with wavefront aberration instruments and corrected using wavefront-guided or wavefront-optimized laser surgery. Wavefront-guided ablations are based on preoperative measurements of HOAs; wavefront-optimized ablations are designed to minimize induction of new HOAs while preserving naturally occurring aberrations. Two wavefront procedures are expected to produce better visual acuity than conventional procedures. OBJECTIVES: The primary objective was to compare effectiveness and safety of wavefront procedures, laser-assisted in-situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) or laser epithelial keratomileusis (LASEK) versus corresponding conventional procedures, for correcting refractive errors in adults for postoperative uncorrected visual acuity, residual refractive errors, and residual HOAs. The secondary objective was to compare two wavefront procedures. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL, which contains the Cochrane Eyes and Vision Trials Register; 2019, Issue 8); Ovid MEDLINE; Ovid Embase; Latin American and Caribbean Health Sciences (LILACS); the ISRCTN registry; ClinicalTrials.gov and the WHO ICTRP. The date of the search was 6 August 2019. We imposed no restrictions by language or year of publication. We used the Science Citation Index (September 2013) and searched the reference lists of included trials to identify additional relevant trials. SELECTION CRITERIA: We included randomized controlled trials (RCTs) comparing either wavefront modified with conventional refractive surgery or wavefront-optimized with wavefront-guided refractive surgery in participants aged ⪰ 18 years with refractive errors. DATA COLLECTION AND ANALYSIS: We used standard Cochrane methodology. MAIN RESULTS: We identified 33 RCTs conducted in Asia, Europe and United States, totaling 1499 participants (2797 eyes). Participants had refractive errors ranging from high myopia to low hyperopia. Studies reported at least one of the following review-specific outcomes based on proportions of eyes: with uncorrected visual acuity (UCVA) of 20/20 or better, without loss of one or more lines of best spectacle-corrected visual acuity (BSCVA), within ± 0.50 diopters (D) of target refraction, with HOAs and adverse events. Study characteristics and risk of bias Participants were mostly women, mean age 29 and 53 years, and without previous refractive surgery, ocular pathology or systemic comorbidity. We could not judge risks of bias for most domains of most studies. Most studies in which both eyes of a participant were analyzed failed to account for correlations between two eyes in the analysis and reporting of outcomes. Findings For the primary comparison between wavefront (PRK or LASIK or LASEK) and corresponding conventional procedures, 12-month outcome data were available from only one study of PRK with 70 participants. No evidence of more favorable outcomes of wavefront PRK on proportion of eyes: with UCVA of 20/20 or better (risk ratio [RR] 1.03, 95% confidence interval (CI) 0.86 to 1.24); without loss of one or more lines of BSCVA (RR 0.94, 95% CI 0.81 to 1.09); within ± 0.5 D of target refraction (RR 1.03, 95% CI 0.86 to 1.24); and mean spherical equivalent (mean difference [MD] 0.04, 95% CI -0.11 to 0.18). The evidence for each effect estimate was of low certainty. No study reported HOAs at 12 months. At six months, the findings of two to eight studies showed that overall effect estimates and estimates by subgroup of PRK or LASIK or LASEK were consistent with those for PRK at 12 month, and suggest no difference in all outcomes. The certainty of evidence for each outcome was low. For the comparison between wavefront-optimized and wavefront-guided procedures at 12 months, the overall effect estimates for proportion of eyes: with UCVA of 20/20 or better (RR 1.00, 95% CI 0.99 to 1.02; 5 studies, 618 participants); without loss of one or more lines of BSCVA (RR 0.99, 95% CI 0.96 to 1.02; I2 = 0%; 5 studies, 622 participants); within ± 0.5 diopters of target refraction (RR 1.02, 95% CI 0.95 to 1.09; I2 = 33%; 4 studies, 480 participants) and mean HOAs (MD 0.03, 95% CI -0.01 to 0.07; I2 = 41%; 5 studies, 622 participants) showed no evidence of a difference between the two groups. Owing to substantial heterogeneity, we did not calculate an overall effect estimate for mean spherical equivalent at 12 months, but point estimates consistently suggested no difference between wavefront-optimized PRK versus wavefront-guided PRK. However, wavefront-optimized LASIK compared with wavefront-guided LASIK may improve mean spherical equivalent (MD -0.14 D, 95% CI -0.19 to -0.09; 4 studies, 472 participants). All effect estimates were of low certainty of evidence. At six months, the results were consistent with those at 12 months based on two to six studies. The findings suggest no difference between two wavefront procedures for any of the outcomes assessed, except for the subgroup of wavefront-optimized LASIK which showed probable improvement in mean spherical equivalent (MD -0.12 D, 95% CI -0.19 to -0.05; I2 = 0%; 3 studies, 280 participants; low certainty of evidence) relative to wavefront-guided LASIK. We found a single study comparing wavefront-guided LASIK versus wavefront-guided PRK at six and 12 months. At both time points, effect estimates consistently supported no difference between two procedures. The certain of evidence was very low for all estimates. Adverse events Significant visual loss or optical side effects that were reported were similar between groups. AUTHORS' CONCLUSIONS: This review suggests that at 12 months and six months postoperatively, there was no important difference between wavefront versus conventional refractive surgery or between wavefront-optimized versus wavefront-guided surgery in the clinical outcomes analyzed. The low certainty of the cumulative evidence reported to date suggests that further randomized comparisons of these surgical approaches would provide more precise estimates of effects but are unlikely to modify our conclusions. Future trials may elect to focus on participant-reported outcomes such as satisfaction with vision before and after surgery and effects of remaining visual aberrations, in addition to contrast sensitivity and clinical outcomes analyzed in this review.

Evaluation of femtosecond laser-assisted anterior capsulotomy in the presence of ophthalmic viscoelastic devices (OVDs).

The introduction of femtosecond laser-assisted cataract surgery is an alternative approach to conventional cataract surgery. Our study aimed to determine the effectiveness of femtosecond laser-assisted capsulotomy in the presence of different ophthalmic viscoelastic devices (OVDs) in the anterior chamber. Fresh porcine eyes (n = 96) underwent LDV Z8-assisted anterior capsulotomy, either in the presence of an OVD (Viscoat, Provisc, Healon, Healon GV or HPMC) or without, using 90% and 150% energies respectively. Following that, the capsule circularity, tag's arc-length, tag-length, tag-area and rupture strength (mN) of the residual capsular bag were evaluated. We found that increasing energy from 90 to 150% across the OVD sub-groups improved the studied capsulotomy parameters. Amongst the 90% energy sub-groups, the circularity and tag-parameters were worse with Viscoat and Healon GV, which have higher refractive index and viscosity compared to the aqueous humour. Using 150% energy, Healon GV showed a significantly worse total arc-length (p = 0.01), total tag-length (p = 0.03) and total tag-area (p = 0.05) compared to the control group. We concluded that; an OVD with a refractive index similar to aqueous humour and lower viscosity, such as Healon or Provisc, as well as a higher energy setting, are recommended, to enhance the efficacy of laser capsulotomy.

Comparison of the Levels of Transforming Growth Factor-ß1 in Tear Fluid in Patients with High Myopia after Transepithelial Photorefractive Keratectomy and Laser Subepithelial Keratomileusis (LASEK).

We compared the level of transforming growth factor-ß1 (TGF-ß1) in the tear fluid of 20 patients with high myopia who underwent transepithelial photorefractive keratectomy (T-PRK) in one eye and laser subepithelial keratomileusis (LASEK) in the contralateral eye. Tear fluid samples were collected with scaled microcapillary tubes before (day 0) and on days 1, 3, and 5 after surgery. The release of TGF-ß1 was determined by multiplying the concentration of TGF-ß1 by capillary tear fluid flow. Corneal haze was also evaluated in 1, 3, and 6 months after surgeries. The median TGF-ß1 release after T-PRK and LASEK differed significantly on days 1 and 3 (p<0.005) and on day 5 (p<0.05). The mean corneal haze score after T-PRK and LASEK also significantly differed in 1 month (p<0.005), but no significant differences in this parameter were revealed at later terms. Thus, the level of TGF-ß1 in the tear fluid after T-PRK was lower than after LASEK, which can be the cause of less pronounced corneal haze in 1 month after surgery.

Laser in Situ Keratomileusis and Surface Ablation in Breastfeeding Patients.

PURPOSE: Our objectives were to determine the anatomical and functional (visual and refractive) outcomes of corneal refractive surgery during breastfeeding and to compare the results with those of women who stopped breastfeeding at least 3 months before the procedure. We also evaluated predictability, safety, and efficacy indexes; number of retreatments; and adverse effects reported in babies. METHODS: We performed a multicenter, retrospective, interventional case series review of patients who were breastfeeding and who underwent laser in situ keratomileusis or surface ablation (photorefractive keratectomy) from September 11, 2002 to December 12, 2017 (group 1, n = 142 eyes in the case group). Patients were compared with women who stopped breastfeeding at least 3 months before the procedure from September 11, 2002 to December 12, 2017 (group 2, n = 95 eyes in the control group). A total of 168 women (237 eyes) were included. Patients were incorporated consecutively. Functional (visual and refractive) and anatomical outcomes are described. RESULTS: No significant intraoperative or postoperative complications were recorded. There were no significant differences between the groups in visual acuity, postoperative spherical equivalent, efficacy index, predictability, safety index, or retreatments. No infants experienced adverse effects. CONCLUSIONS: In our experience, laser in situ keratomileusis and photorefractive keratectomy can be performed effectively and safely in breastfeeding women.

Predictors affecting myopic regression in - 6.0D to - 10.0D myopia after laser-assisted subepithelial keratomileusis and laser in situ keratomileusis flap creation with femtosecond laser-assisted or mechanical microkeratome-assisted.

PURPOSE: To investigate the predictive factors of postoperative myopic regression among subjects who have undergone laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) flap created with a mechanical microkeratome (MM), and LASIK flap created with a femtosecond laser (FS). All recruited patients had a manifest spherical equivalence (SE) from - 6.0D to - 10.0D myopia. METHODS: This retrospective, observational case series study analyzed outcomes of refraction at 1 day, 1 week, and 1, 3, 6, and 12 months postoperatively. Predictors affecting myopic regression and other covariates were estimated with the Cox proportional hazards model for the three types of surgeries. RESULTS: The study enrolled 496 eyes in the LASEK group, 1054 eyes in the FS-LASIK group, and 910 eyes in the MM-LASIK group. At 12 months, from - 6.0D to - 10.0D myopia showed that the survival rates (no myopic regression) were 52.19%, 59.12%, and 58.79% in the MM-LASIK, FS-LASIK, and LASEK groups, respectively. Risk factors for myopic regression included thicker postoperative central corneal thickness (P ≦ 0.01), older age (P ≦ 0.01), aspherical ablation (P = 0.02), and larger transitional zone (TZ) (P = 0.03). Steeper corneal curvature (Kmax) (P = 0.01), thicker preoperative central corneal thickness (P < 0.01), smaller preoperative myopia (P < 0.01), longer duration of myopia (P = 0.02), with contact lens (P < 0.01), and larger optical zone (OZ) (P = 0.02) were protective factors. Among the three groups, the MM-LASIK had the highest risk of postoperative myopic regression (P < 0.01). CONCLUSIONS: The MM-LASIK group experienced the highest myopic regression, followed by the FS-LASIK and LASEK groups. Older age, aspheric ablation used, thicker postoperative central corneal thickness, and enlarging TZ contribute to myopic regression; steeper preoperative corneal curvature (Kmax), longer duration of myopia, with contact lens, thicker preoperative central corneal thickness, lower manifest refraction SE, and enlarging OZ prevent postoperative myopic regression in myopia from - 6.0D to - 10.0D.

Comparing Dry Eye Disease After Small Incision Lenticule Extraction and Laser Subepithelial Keratomileusis.

PURPOSE: To compare dry eye disease parameters between small incision lenticule extraction (SMILE) and laser subepithelial keratomileusis (LASEK). METHODS: This prospective, nonrandomized study included 39 eyes of 39 patients who underwent SMILE (n = 19) and LASEK (n = 20). Dry eye disease parameters included Ocular Surface Disease Index (OSDI), tear breakup time, Schirmer I test (SIT) value, corneal esthesiometry result, tear meniscus area, meibomian gland evaluation result, lipid layer thickness, and blink rate. Evaluations were performed before surgery and at 1 and 6 months after surgery. RESULTS: Compared with the LASEK group, the SMILE group showed lower corneal esthesiometry values at 1 month and higher OSDI scores and lower SIT values at 6 months after surgery. The SMILE group showed significantly higher OSDI scores at 1 and 6 months after surgery than before, but significantly lower OSDI scores at 6 months than at 1 month after surgery. Both groups showed significantly decreased corneal sensitivity at 1 month after surgery, which increased to the preoperative level 6 months after surgery. The change in OSDI scores at 1 month after surgery positively correlated with changes in the total and partial blink rates, whereas the change in corneal sensitivity at 1 month after surgery negatively correlated with the total and partial blink rates. CONCLUSIONS: Both SMILE and LASEK groups showed temporary decreases in corneal sensitivity, which recovered to baseline levels. Although subjective symptoms worsened after SMILE, SIT values improved after LASEK. Compared with SMILE, LASEK yielded better results regarding subjective symptoms, tear production, and corneal sensitivity.

Predictors of Myopic Regression for Laser-assisted Subepithelial Keratomileusis and Laser-assisted in Situ Keratomileusis Flap Creation with Mechanical Microkeratome and Femtosecond Laser in Low and Moderate Myopia.

Purpose: To determine the predictive factors of postoperative myopic regression in subjects who have undergone laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) with flaps created using a mechanical microkeratome (MM) or LASIK with flaps created using a femtosecond (FS) laser for -0.50 D to -6.0 D myopia.Materials and Methods: This study was designed as a retrospective comparison. We included 236 eyes in the LASEK group, 1,178 eyes in the MM-LASIK group and 1,333 eyes in the FS-LASIK group. Refractive outcomes were recorded at one day; one week; and one, three, six and 12 months postoperatively. Predictors affecting myopic regression and other covariates were estimated using a Cox proportional hazards model for the three methods of surgery.Results: At 12 months, the survival rates (no myopic regression) were 63.36%, 74% and 77% in the MM-LASIK, LASEK, and FS-LASIK groups, respectively. Risk factors for myopic regression were indicated for patients with greater preoperative central corneal thicknesses (CCT) (P = .02), female patients (P < .01), patients with aspherical ablations (P = .01) and those with larger transitional zones (TZ) (P < .01). Among the three surgeries, MM-LASIK had a significantly higher probability of postoperative myopic regression (P < .01). Longer durations of myopia (P = .03), steeper corneal curvatures (Kmax) (P < .01) and larger optical zones (OZ) (P < .01) were protective factors.Conclusion: MM-LASIK had the highest risk for myopic regression. OZ, TZ, aspherical ablations, preoperative corneal curvatures and being a female patient had significant influence on myopic regression in -0.50 D to -6.0 D myopia.

Myopic Laser-Assisted Subepithelial Keratectomy (LASEK) outcomes using three different excimer laser platforms: a retrospective observational study.

BACKGROUND: To compare the visual and refractive outcomes after myopic LASEK using three different excimer lasers and standardized surgical and mitomycin C (MMC) application protocols. METHODS: In this retrospective, observational cohort study, we examined 122 eyes treated with Allegretto, 135 eyes treated with Esiris and 137 eyes treated with Technolas excimer lasers. All eyes were treated under the same surgical protocol, and a standardized MMC dosage was used. The three groups were refraction-matched, and both visual and refractive outcomes were evaluated at 1 and 7 days and 1 and 3 months after surgery. RESULTS: At 3 months postsurgery, Allegretto provided significantly better outcomes than Esiris and Technolas in terms of postoperative uncorrected distance visual acuity (UDVA) (1.11 ± 0.2 vs 1.01 ± 0.2 vs 0.98 ± 0.2) (P = 0.0001), corrected distance visual acuity (CDVA) (1.13 ± 0.2 vs 1.10 ± 0.1 vs 1.04 ± 0.2) (P = 0.0001), residual sphere (- 0.01 ± 0.2 vs + 0.29 ± 0.7 vs + 0.27 ± 0.6) (P = 0.0001), and efficacy index (0.99 ± 0.2 vs 0.90 ± 0.2 vs 0.91 ± 0.2) (P = 0.0004). CONCLUSIONS: We found slightly better visual and refractive outcomes in the Allegretto group at 3 months post-op after LASEK with MMC to correct myopia.

Corneal biomechanical properties after SMILE versus FLEX, LASIK, LASEK, or PRK: a systematic review and meta-analysis.

BACKGROUND: The aim of this study was to compare the postoperative corneal biomechanical properties between small incision lenticule extraction (SMILE) and other corneal refractive surgeries. METHODS: A systematic review and meta-analysis were conducted. Articles from January 2005, to April 2019, were identified searching PubMed, EMBASE, Web of Science, and International Clinical Trials Registry Platform. Studies that compared SMILE with other corneal refractive surgeries on adult myopia patients and evaluated corneal biomechanics were included. Multiple effect sizes in each study were combined. Random-effects model was conducted in the meta-analysis. RESULTS: Twenty-two studies were included: 5 randomized controlled trials (RCTs), 9 prospective and 6 retrospective cohort studies, and 2 cross-sectional studies. Using the combined effect of corneal hysteresis (CH) and corneal resistance factor (CRF), which were obtained from ocular response analyzer (ORA), the pooled Hedges' g of SMILE versus femtosecond laser-assisted in situ keratomileusis (FS-LASIK) was 0.41 (95% CI, 0.00 to 0.81; p = 0.049; I2 = 78%), versus LASIK was 1.31 (95% CI, 0.54 to 2.08; p < 0.001; I2 = 77%), versus femtosecond lenticule extraction (FLEX) was - 0.01 (95% CI, - 0.31 to 0.30; p = 0.972; I2 = 20%), and versus the group of photorefractive keratectomy (PRK) and laser-assisted sub-epithelial keratectomy (LASEK) was - 0.26 (95% CI, - 0.67 to 0.16; p = 0.230; I2 = 54%). The summary score of Corvis ST (CST) after SMILE was comparable to FS-LASIK/LASIK with the pooled Hedges' g = - 0.05 (95% CI, - 0.24 to 0.14; p = 0.612, I2 = 55%). CONCLUSIONS: In terms of preserving corneal biomechanical strength after surgeries, SMILE was superior to either FS-LASIK or LASIK, while comparable to FLEX or PRK/LASEK group based on the results from ORA. More studies are needed to apply CST on evaluating corneal biomechanics after refractive surgeries.

LASEK-mitomicina C versus PRK-mitomicina C en pacientes con miopía o astigmatismo miópico compuesto / LASEK-mitomycin C versus PRK-mitomycin C in patients with myopia or compound myopic astigmatism

RESUMEN Objetivo: Evaluar los resultados relacionados con la efectividad y la seguridad en el tratamiento con queratectomía subepitelial asistida por láser con mitomicina C versus queratectomía fotorreactiva con mitomicina C en ojos con miopía o astigmatismo miópico compuesto. Métodos: Se realizó un estudio experimental, longitudinal y prospectivo en el Instituto Cubano de Oftalmología Ramón Pando Ferrer entre abril del año 2016 y abril de 2017. Se empleó un muestreo aleatorio simple por el cual se obtuvo la técnica quirúrgica a realizar. El primer ojo operado fue el derecho y a la semana se realizó la cirugía en el ojo izquierdo, en el cual se aplicó la otra técnica quirúrgica. Esto permitió realizar en cada paciente ambas técnicas quirúrgicas. La muestra quedó constituida por 146 ojos (73 pacientes) que cumplían con los criterios de selección. Resultados: El comportamiento preoperatorio entre los dos grupos fue muy similar. En ninguno de los casos existieron diferencias en las variables que se evaluaron (agudeza visual sin corrección, agudeza visual mejor corregida, esfera, cilindro y equivalente esférico). La diferencia entre los valores preoperatorios y los encontrados a los 6 meses del tratamiento quirúrgico en cada grupo fueron estadísticamente significativos (p= 0,000) para todas las variables analizadas, excepto para la agudeza visual mejor corregida en el grupo de ojos tratados con láser con mitomicina C (p= 0,083). El haze y el defecto de epitelización fueron los dos tipos de complicaciones observadas. Conclusiones: Se demostró que ambas técnicas quirúrgicas son efectivas y seguras(AU)

ABSTRACT Objective: Evaluate the effectiveness and safety of laser-assisted subepithelial keratectomy with mitomycin C vs. photoreactive keratectomy with mitomycin C in eyes with myopia or compound myopic astigmatism. Methods: An experimental prospective longitudinal study was conducted at Ramón Pando Ferrer Cuban Institute of Ophthalmology from April 2016 to April 2017. Simple random sampling was used to decide on the surgical technique to be applied. Surgery was first performed on the right eye using one of the techniques, and then one week later on the left eye with the other technique. That way each patient could undergo both surgical techniques. The sample was composed of 146 eyes (73 patients) meeting the inclusion criteria. Results: Preoperative behavior was very similar in the two groups. In neither case were differences found in the variables analyzed (uncorrected visual acuity, best corrected visual acuity, sphere, cylinder and spherical equivalent). The differences between preoperative values and those found six months after surgery in each group were statistically significant for all the variables analyzed (p= 0.000), except for best corrected visual acuity in the group of eyes treated with laser with mitomycin C (p= 0.083). Haze and epithelization defect were the two types of complications observed. Conclusions: It was demonstrated that both surgical techniques are effective and safe(AU)

Comparative study of wave-front aberration and corneal Asphericity after SMILE and LASEK for myopia: a short and long term study.

BACKGROUND: The study compares the wave-front aberration and corneal asphericity from multiple perspectives after Small Incision Lenticule Extraction and Laser-assisted Subepithelial Keratomileusis for mild to moderate myopia in a short and long time period. METHODS: This prospective and comparative study included 32 eyes in the SMILE group, with a mean spherical equivalent (SE) of - 4.1 ± 0.9D and 32 eyes in the LASEK group, with a mean SE of - 3.7 ± 1.0D. Visual acuity, refractive error, wave-front aberration, corneal Q value and corneal refractive power were analyzed pre-, 3 months and 3 years post-operatively. RESULTS: There was no significant difference in refractive error, wave-front aberration, corneal Q value and corneal refractive power before treatment. Three months postoperative, Q value within 6 mm (SMILE: 0.46 ± 0.27, LASEK: 0.63 ± 0.28, p = 0.02), the relative peripheral corneal power (5-8 mm: p < 0.05), change of higher order aberration (SMILE: 0.10 ± 0.16, LASEK: 0.24 ± 0.20, p = 0.004) and spherical aberration (SA, SMILE: -0.07 ± 0.30, LASEK: -0.41 ± 0.40, p < 0.001) were significantly lower in the SMILE than in LASEK group. The visual acuity, refractive error, coma, peripheral Q value, central corneal power had no significant difference between the two groups. Three years post-operation, the corneal power distribution results and SA were similar to that of 3-month, while the Q value had no significant difference between the two groups. CONCLUSION: In the early stage after SMILE, the HOAs was lower, the corneal refractive power from central to periphery was more uniform than after LASEK; and in the long-term run, SMILE still preceded LASEK in the corneal asphericity and aberration.

Comparison of the posterior corneal elevation and biomechanics after SMILE and LASEK for myopia: a short- and long-term observation.

PURPOSE: This study compares the posterior corneal elevation and corneal biomechanics after small incision lenticule extraction (SMILE) and laser-assisted subepithelial keratomileusis (LASEK) for myopia correction in a short- and long-term observation. METHODS: This prospective study included 32 patients in the SMILE group and 32 patients in the LASEK group. Corneal posterior central elevation (PCE), posterior mean elevation (PME), corneal back power (Kb), and anterior chamber depth (ACD) were evaluated with Pentacam, and intraocular pressure (IOP), corneal hysteresis (CH), and corneal resistance factor (CRF) were evaluated with the ORA at pre-operation and 3 months and 3 years post-operation. RESULTS: Three months post-operatively, CH, CRF, and IOP decreased significantly and central posterior surface shifted backward in both groups (p < 0.05). CH was lower in the LASEK group (p = 0.03) and change of CH and CRF per unit corneal tissue removed (ΔCH/ablation depth (AD) and ΔCRF/AD) was lower in SMILE than in LASEK (p = 0.01, 0.03). Three years post-operatively, the PME shifted more posteriorly in LASEK (p = 0.04), but was stable in SMILE (p = 0.06). Kb flattened and ACD was shallower in both groups (compared to preoperative data, p < 0.001). CH in the LASEK group increased and is comparable to that in the SMILE group at 3 years post-operative. CONCLUSION: Both SMILE and LASEK can change the posterior surface and corneal biomechanics. SMILE may have less influence on corneal biomechanics than LASEK at an early stage post-operative in terms of per unit corneal tissue removed, but the effect became comparable in a long-term observation.

Femtosecond laser-assisted sub-Bowman keratomileusis versus laser-assisted subepithelial keratomileusis to correct myopic astigmatism.

PURPOSE: To compare femtosecond laser-assisted sub-Bowman keratomileusis (FSBK) versus laser-assisted subepithelial keratomileusis (LASEK) to correct moderate to high myopic astigmatism. METHODS: Retrospective, nonrandomized, interventional, comparative case series. A total of eight hundred and fifty-two eyes with myopic astigmatism of -1.5 diopters (D) or higher were included in the study. We compared 427 eyes treated with FSBK versus 425 eyes treated with LASEK with or without mitomycin C. Visual and refractive results were evaluated 1 day, 1 week, 3 and 6 months postoperatively. RESULTS: Six months postoperatively, the residual spherical defect was slightly but significantly higher in the LASEK group (+0.15±0.62D) than in the FSBK group (+0.09±0.35D) (P=0.05). The postoperative residual astigmatism was also slightly but significantly higher in the LASEK group (-0.38±0.52D) than in the FSBK group (-0.26±0.45D) (P=0.0005). No significant differences were found in the efficacy (0.98±0.17 versus 0.98±0.36, P=0.6) and safety indexes (1.04±0.16 versus 1.05±0.37, P=0.1) between FSBK and LASEK. The enhancement rate was significantly higher in the FSBK group (22.6%) than in the LASEK group (15.5%) (P=0.01). CONCLUSIONS: Both FSBK and LASEK are safe and effective procedures to correct moderate to high myopic astigmatism. Slightly better visual and refractive results were observed in FSBK-treated eyes in a 6-month follow-up.

Effect of Iris registration on visual outcome in wavefront-guided LASEK for myopic astigmatism.

PURPOSE: This study aimed to investigate the effect of iris registration (IR) on visual outcomes in wavefront-guided LASEK for myopic astigmatism. METHODS: The retrospective chart review was performed for wavefront-guided LASEK using VISX Star S4 in patients with myopic astigmatism (cylinder ≥ 1.00 diopter[D]). Eyes were divided into IR group (LASEK with IR at the time of surgery) and Non-IR group (LASEK without IR system + failed-IR engagement during LASEK). Visual acuity (VA), astigmatism, higher-order aberration (HOA), and contrast sensitivity were assessed preoperatively and 3 months postoperatively. The IR and Non-IR groups were subcategorized depending on the spherical equivalent (lower myopia ≤-5.00 D vs. higher myopia >-5.00 D) for the comparison of HOA changes. RESULTS: Postoperative uncorrected VAs showed no differences between IR (n = 30) and Non-IR (n = 46). In astigmatic vector analyses, no differences were noted in the mean magnitude of error and the mean angle of error between two groups. There were no differences in postoperative total HOA, spherical aberration (SA), coma, and trefoil between the groups, either. The total HOA and SA increased in both groups, while coma increased only in Non-IR. In higher myopia, ΔRMS of coma was smaller in IR. Preoperative and postoperative total HOA were linearly correlated in Non-IR, but not for IR. Contrast sensitivity of 12 cycles per degree improved in both groups. CONCLUSION: IR had similar outcomes to conventional trackers in wavefront-guided LASEK, with less tendency of inducing coma, especially in higher myopia.

Influence of LASEK on Schiøtz, Goldmann and dynamic contour Tonometry.

PURPOSE: Our purpose was to assess the effect of LASEK surgery on ocular rigidity and to compare its effect on intraocular pressure (IOP) readings with Goldmann applanation tonometry (GAT), Schiøtz indentation tonometry (ST) and dynamic contour tonometry (DCT). METHODS: Prospective, observational, single-masked cohort study. One eye per patient from 31 consecutive subjects who underwent LASEK refractive surgery to correct myopia, as well as from 108 non-operated myopic patients, were included. IOP was measured using GAT, DCT, and ST. The coefficient of ocular rigidity (Ko) was obtained from the regression line of the three readings obtained with each weight of the ST. Linear multiple regression analysis was performed with dummy variables to assess the effect of age, central corneal thickness (CCT), and previous refractive surgery on IOP values. RESULTS: Age, CCT, and LASEK surgery explained 23% of the IOP readings with GAT, 11% with DCT, and had no significant influence on ST readings. The IOP readings obtained with GAT and DCT, but not with ST, were significantly different between LASEK and control groups. Significant differences in Ko were observed between LASEK (0.014 mmHg/µL ±0.007) and control groups (0.021 mmHg/µL ±0.013) (P = 0.001). Ko values were not related with age or CCT, in either LASEK or control groups. CONCLUSIONS: ST readings seems to be less affected by LASEK surgery than the other tonometers evaluated. There is a difference in the ocular rigidity between the control and the LASEK eyes that it is not correlated with CCT, so it seems that ST can detect changes in the biomechanical behavior of the LASEK operated corneas.

Long-term Follow-up of LASEK With Mitomycin C Performed to Correct Myopia in Thin Corneas.

PURPOSE: To evaluate the long-term outcomes of laser-assisted subepithelial keratomileusis (LASEK) with intraoperative use of mitomycin C (MMC) performed on thin corneas for the correction of myopia. METHODS: This retrospective cohort study included 100 eyes with a preoperative central corneal thickness (CCT) thinner than 500 µm that underwent LASEK + MMC with at least 6 years of follow-up. Stability of visual acuity and refraction and the efficacy, safety, and predictability at the examinations 3 months and the last annual postoperative visit were analyzed. RESULTS: Preoperative CCT was 482.9 ± 14.7 µm (range: 433 to 499 µm). Mean preoperative spherical equivalent was -4.09 ± 2.3 diopters (D). At the 3-month postoperative visit, mean CCT was 419.79 ± 32.6 µm. The residual spherical equivalent showed a statistically significant regression (P = .001) in the comparison between the 3-month and the last annual postoperative visit. The efficacy index showed a significant decrease (P = .01) and the safety index remained stable around 0.96. Six or more years after the surgery, 85 eyes (85%) were within ±0.50 D and 94 eyes (94%) eyes were within ±1.00 D of emmetropia. The topography did not show signs of secondary corneal ectasia in any eye. CONCLUSIONS: LASEK with intraoperative use of MMC seems to be safe, effective, and predictable to correct myopia in corneas thinner than 500 µm and with normal preoperative topography, providing good visual and refractive outcomes with no topographic signs of corneal ectasia in a mean 6.5-year follow-up. [J Refract Surg. 2017;33(12):813-819.].