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.

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.

Comparison of Higher-Order Aberrations after LASEK between Two Different Laser Platforms for Low-to-Moderate Myopia.

PURPOSE: To compare the differences in higher-order aberrations (HOAs) after laser subepithelial keratomileusis (LASEK) between two different laser platforms. METHODS: One hundred and seven eyes of 107 patients were included in this study. Fifty-six eyes underwent LASEK with the Triple-A profile (an ablation profile of the MEL 90 excimer laser) and 51 eyes underwent LASEK with the aspheric (Aberration Smart Ablation [ASA]) profile. Uncorrected distance visual acuity, corrected distance visual acuity (CDVA), corneal topography, and ocular aberrations were measured before and 6 months postoperatively. RESULTS: In the ASA group, the values of horizontal trefoil, vertical coma, horizontal coma, spherical aberrations, and total HOAs increased significantly after surgery (all P < 0.05). There were no significant differences in the vertical trefoil between the preoperative and 6-month postoperative periods. In the Triple-A group, there were no differences in vertical trefoil and horizontal trefoil values between the preoperative and 6-month postoperative periods. Compared with the preoperative values, vertical coma, horizontal coma, spherical aberrations, and total HOAs were significantly increased at 6 months after surgery (all P < 0.05). Compared to the Triple-A group, higher horizontal trefoil and horizontal coma were introduced in the ASA group at 6 months postoperatively. CONCLUSION: The Triple-A ablation profile of the MEL 90 excimer laser at a 500-Hz pulse rate was an efficient method to correct myopia, especially for mild-to-moderate myopia, compared with the aspheric ablation model, fewer horizontal trefoil and horizontal coma were induced at 6 months after LASEK. ABBREVIATIONS: HOAs, Higher-Order Aberrations; LASEK, laser subepithelial keratomileusis; ASA, Aberration Smart Ablation; UDVA, uncorrected distance visual acuity; CDVA, corrected distance visual acuity.

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.

Effect of age on visual and refractive results after laser-assisted subepithelial keratomileusis (LASEK) with adjuvant use of mitomycin C / Efecto de la edad en los resultados visuales y refractivos después de la queratomileusis subepitelial asistida por láser (LASEK) con el uso adyuvante de mitomicina C

Purpose: To evaluate the influence of age on visual and refractive results after laser-assisted subepithelial keratomileusis (LASEK) with the adjuvant use of mitomycin C (MMC) for the correction of myopia. Methods: Retrospective, nonrandomized, cohort study. A total of 1374 eyes treated with LASEK+MMC were included in the study (we compared 1163 eyes of patients aged 18 to 40 years versus 211 eyes of patients over 40 years). Visual and refractive results were evaluated at the 6-month postoperative visit. Results: Six months postoperatively, both the uncorrected distance visual acuity and the corrected distance visual acuity were significantly better in the group of young patients ( P= 0.0001). We found a slight tendency to overcorrection in the group of young patients compared to a slight tendency to undercorrection in the group of patients over 40 years (P = 0.002). The efficacy index was significantly better in the group of younger patients (0.91 ± 0.2) than in the older patients (0.86±0.2) (P = 0.0001). No significant difference was found in the safety index between groups. 81.5% of eyes in the group of patients aged 18 to 40 years compared to 75.3% of eyes in the group of patients aged >40 years were within ± 0.5D of emmetropia ( P= 0.001). Conclusions: A tendency toward undercorrection and less predictability was found with aging after myopic LASEK with MMC for the correction of myopia

Objetivo: Evaluar la influencia de la edad sobre los resultados visuales y refractivos tras queratomileusis subepitelial asistida por láser (LASEK) con uso adyuvante de mitomicina C (MMC) para la corrección de la miopía. Métodos: Estudio de cohorte retrospectivo y no aleatorizado. Se incluyó en el estudio a un total de 1.374 ojos tratados con LASEK + MMC (comparamos 1.163 ojos de pacientes de edades comprendidas entre 18 y 40 años, con 211 ojos de pacientes mayores de 40 años). Los resultados visuales y refractivos se evaluaron durante la visita postoperatoria transcurridos 6 meses. Resultados: A los seis meses de la intervención, tanto la agudeza visual de lejos no corregida como corregida fueron mejores en el grupo de pacientes jóvenes (P = 0,0001). Encontramos una ligera tendencia hacia la sobre-corrección en el grupo de pacientes jóvenes, en comparación a una ligera tendencia hacia la infra-corrección en el grupo de pacientes mayores de 40 años (P = 0,002). El índice de eficacia fue significativamente mejor en el grupo de pacientes jóvenes (0,91 ± 0,2) que en el de pacientes mayores (0,86 ± 0,2) (P = 0,0001). No se encontró diferencia significativa en cuanto al índice de seguridad entre grupos. El 81,5% de los ojos del grupo de pacientes con edades comprendidas entre 18 y 40, en comparación con el 75,3% de los ojos en el grupo de pacientes mayores de >40 años, reflejó un valor±0,5D de emetropía (P = 0,001). Conclusiones: Se encontró una tendencia hacia la infra-corrección y menor predecibilidad con la edad tras la realización de LASEK con MMC para la corrección de la miopía

Predictability and stability of laser-assisted subepithelial keratectomy with mitomycin C for the correction of high myopia.

The purpose of this study was to evaluate the predictability and stability of laser-assisted subepithelial keratectomy (LASEK) with mitomycin C (MMC) in correction of high myopia (≤-6.0 diopters [D]) as compared to low-to-moderate myopia (>-6.0 D).This is a retrospective, comparative, cohort study which included 43 eyes of 43 consecutive patients who underwent LASEK with MMC in a private hospital in Hong Kong by a single surgeon. Twenty-five eyes had high myopia (mean spherical equivalent [SE] = -8.53 ±â€Š1.82 D) and 18 eyes had low-to-moderate myopia (mean SE = -3.99 ±â€Š1.37 D) before surgery.In terms of refractive predictability, mean SE was significantly better in eyes with preoperative low-to-moderate myopia than high myopia at 6 months (0.04 ±â€Š0.23 vs 0.31 ±â€Š0.52 D, P = .035). In terms of refractive stability, between 1 and 3 months, both groups had mean absolute change of SE of around 0.25 D. Between 3 and 6 months, preoperative low-to-moderate myopia group had significantly less absolute change of SE compared to high myopia group (0.07 vs 0.23 D, P = .003). More eyes with preoperative high myopia changed SE by more than 0.25 D than those with low-to-moderate myopia between 3 and 6 months (32.0% vs 5.6%, P = .057).In conclusion, LASEK with MMC is more unpredictable and unstable in correction of high myopia than low-to-moderate myopia. The refractive outcome of most low-to-moderate myopia correction stabilizes at 3 months. Stability is not achieved until after 6 months in high myopia correction.

Laser-assisted subepithelial keratectomy (LASEK) versus laser-assisted in-situ keratomileusis (LASIK) for correcting myopia.

BACKGROUND: Near-sightedness, or myopia, is a condition in which light rays entering the eye along the visual axis focus in front of the retina, resulting in blurred vision. Myopia can be treated with spectacles, contact lenses, or refractive surgery. Options for refractive surgery include laser-assisted subepithelial keratectomy (LASEK) and laser-assisted in-situ keratomileusis (LASIK). Both procedures utilize a laser to shape the corneal tissue (front of the eye) to correct refractive error, and both create flaps before laser treatment of corneal stromal tissue. Whereas the flap in LASEK is more superficial and epithelial, in LASIK it is thicker and also includes some anterior stromal tissue. LASEK is considered a surface ablation procedure, much like its predecessor, photorefractive keratectomy (PRK). LASEK was developed as an alternative to PRK to address the issue of pain associated with epithelial debridement used for PRK. Assessing the relative benefits and risks/side effects of LASEK and LASIK warrants a systematic review. OBJECTIVES: To assess the effects of LASEK versus LASIK for correcting myopia. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Eyes and Vision Trials Register (2016, Issue 10); MEDLINE Ovid (1946 to 24 October 2016); Embase.com (1947 to 24 October 2016); PubMed (1948 to 24 October 2016); LILACS (Latin American and Caribbean Health Sciences Literature Database; 1982 to 24 October 2016); the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), last searched 20 June 2014; ClinicalTrials.gov (www.clinicaltrials.gov); searched 24 October 2016; and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 24 October 2016. We did not use any date or language restrictions in the electronic searches for trials. SELECTION CRITERIA: We considered only randomized controlled trials (RCTs) for the purposes of this review. Eligible RCTs were those in which myopic participants were assigned randomly to receive either LASEK or LASIK in one or both eyes. We also included paired-eye studies in which investigators randomly selected which of the participant's eyes would receive LASEK or LASIK and assigned the other eye to the other procedure. Participants were men or women between the ages of 18 and 60 years with myopia up to 12 diopters (D) and/or myopic astigmatism of severity up to 3 D, who did not have a history of prior refractive surgery. DATA COLLECTION AND ANALYSIS: Two review authors independently screened all reports and assessed the risk of bias in trials included in this review. We extracted data and summarized findings using risk ratios (RRs) for dichotomous outcomes and mean differences (MDs) for continuous outcomes. In the absence of clinical and methodological heterogeneity across trials, we used a random-effects model to calculate summary effect estimates. We used a fixed-effect model when including fewer than three trials in a meta-analysis. When clinical, methodological, or statistical heterogeneity was observed across trials, we reported our findings in a narrative synthesis. MAIN RESULTS: We identified four eligible trials with 538 eyes of 392 participants for the review, but only three trials (154 participants) provided outcome data for analysis. We found no ongoing trials. Two of four trials were from China, one trial was from Turkey, and the location of one trial was not reported. The risk of bias for most domains was unclear due to poor reporting of trial methods; no trial had a protocol or trial registry record. Three trials enrolled participants with mild to moderate myopia (less than -6.50 D); one trial included only participants with severe myopia (more than -6.00 D).The evidence showed uncertainty in whether there is a difference between LASEK and LASIK in uncorrected visual acuity (UCVA) at 12 months, the primary outcome in our review. The RR and 95% confidence interval (CI) at 12 months after surgery was 0.96 (95% CI 0.82 to 1.13) for UCVA of 20/20 or better and 0.90 (95% CI 0.67 to 1.21) for UCVA of 20/40 or better based on data from one trial with 57 eyes (very low-certainty evidence). People receiving LASEK were less likely to achieve a refractive error within 0.5 diopters of the target at 12 months follow-up (RR 0.69, 95% CI 0.48 to 0.99; 57 eyes; very low-certainty evidence). One trial reported mild corneal haze at six months in one eye in the LASEK group and none in the LASIK group (RR 2.11, 95% CI 0.57 to 7.82; 76 eyes; very low-certainty evidence). None of the included trials reported postoperative pain score or loss of visual acuity, spherical equivalent of the refractive error, or quality of life at 12 months.Refractive regression, an adverse event, was reported only in the LASEK group (8 of 37 eyes) compared with none of 39 eyes in the LASIK group in one trial (low-certainty evidence). Other adverse events, such as corneal flap striae and refractive over-correction, were reported only in the LASIK group (5 of 39 eyes) compared with none of 37 eyes in the LASEK group in one trial (low-certainty evidence). AUTHORS' CONCLUSIONS: Overall, from the available RCTs, there is uncertainty in how LASEK compares with LASIK in achieving better refractive and visual results in mildly to moderately myopic participants. Large, well-designed RCTs would be required to estimate the magnitude of any difference in efficacy or adverse effects between LASEK and LASIK for treating myopia or myopic astigmatism.

Visual Outcomes After SMILE, LASEK, and LASEK Combined With Corneal Collagen Cross-Linking for High Myopic Correction.

PURPOSE: To compare the visual and refractive outcomes of small-incision lenticule extraction (SMILE), laser-assisted subepithelial keratomileusis (LASEK), and LASEK combined with corneal collagen cross-linking (LASEK-CXL) surgery for high-degree myopia. METHODS: Medical records of patients with spherical equivalent (SE) greater than -6.00 diopters (D) treated with SMILE, LASEK, and LASEK-CXL were reviewed. Uncorrected distance visual acuity (UCVA), SE, and corneal haze were followed up in the 3 groups for 6 months. RESULTS: The SMILE group included 69 eyes, the LASEK group included 61 eyes, and the LASEK-CXL group included 40 eyes. At 6 months postoperatively, there were no statistically significant differences in UCVA between the SMILE, LASEK, and LASEK-CXL groups (logMAR 0.00 ± 0.00, 0.01 ± 0.08, and 0.01 ± 0.08, respectively, P = 0.69). The averages of the absolute value of SE were 0.34 ± 0.25 D, 0.50 ± 0.36 D, and 0.42 ± 0.34 D in the SMILE, LASEK, and LASEK-CXL groups, respectively (P = 0.04). The percentages of the patients with a postoperative residual refractive error within ±0.50 D were 84% in the SMILE group, 65% in the LASEK group, and 76% in the LASEK-CXL group. The percentages of the patients with greater than 20/25 postoperative UCVA were 100%, 91%, and 95%, respectively. SMILE produced no postoperative corneal haze. However, 18% of patients treated with LASEK and 25% of those treated with LASEK-CXL had corneal haze at 6 months postoperatively. CONCLUSIONS: SMILE, LASEK, and LASEK-CXL surgery appear to be safe and effective for high-degree myopic correction. However, the SMILE group had no haze and fewer induction of some higher-order aberrations compared with the LASEK and LASEK-CXL groups.

Laser-assisted subepithelial keratectomy (LASEK) versus photorefractive keratectomy (PRK) for correction of myopia.

BACKGROUND: Myopia (near-sightedness or short-sightedness) is a condition in which the refractive power of the eye is greater than required. The most frequent complaint of people with myopia is blurred distance vision, which can be eliminated by conventional optical aids such as spectacles or contact lenses, or by refractive surgery procedures such as photorefractive keratectomy (PRK) and laser epithelial keratomileusis (LASEK). PRK uses laser to remove the corneal stroma. Similar to PRK, LASEK first creates an epithelial flap and then replaces it after ablating the corneal stroma. The relative benefits and harms of LASEK and PRK, as shown in different trials, warrant a systematic review. OBJECTIVES: The objective of this review is to compare LASEK versus PRK for correction of myopia by evaluating their efficacy and safety in terms of postoperative uncorrected visual acuity, residual refractive error, and associated complications. SEARCH METHODS: We searched CENTRAL (which contains the Cochrane Eyes and Vision group Trials Register) (2015 Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to December 2015), EMBASE (January 1980 to December 2015), Latin American and Caribbean Health Sciences (LILACS) (January 1982 to December 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 15 December 2015. We used the Science Citation Index and searched the reference lists of the included trials to identify relevant trials for this review. SELECTION CRITERIA: We included in this review randomized controlled trials (RCTs) comparing LASEK versus PRK for correction of myopia. Trial participants were 18 years of age or older and had no co-existing ocular or systemic diseases that might affect refractive status or wound healing. DATA COLLECTION AND ANALYSIS: Two review authors independently screened all reports and assessed the risk of bias of trials included in this review. We extracted data and summarized findings using risk ratios and mean differences. We used a random-effects model when we identified at least three trials, and we used a fixed-effect model when we found fewer than three trials. MAIN RESULTS: We included 11 RCTs with a total of 428 participants 18 years of age or older with low to moderate myopia. These trials were conducted in the Czech Republic, Brazil, Italy, Iran, China, Korea, Mexico, Turkey, USA, and UK. Investigators of 10 out of 11 trials randomly assigned one eye of each participant to be treated with LASEK and the other with PRK, but did not perform paired-eye (matched) analysis. Because of differences in outcome measures and follow-up times among the included trials, few trials contributed data for many of the outcomes we analyzed for this review. Overall, we judged RCTs to be at unclear risk of bias due to poor reporting; however, because of imprecision, inconsistency, and potential reporting bias, we graded the quality of the evidence from very low to moderate for outcomes assessed in this review.The proportion of eyes with uncorrected visual acuity of 20/20 or better at 12-month follow-up was comparable in LASEK and PRK groups (risk ratio (RR) 0.98, 95% confidence interval (95% CI) 0.92 to 1.05). Although the 95% CI suggests little to no difference in effect between groups, we judged the quality of the evidence to be low because only one trial reported this outcome (102 eyes). At 12 months post treatment, data from two trials suggest no difference or a possibly small effect in favor of PRK over LASEK for the proportion of eyes achieving ± 0.50 D of target refraction (RR 0.93, 95% CI 00.84 to 1.03; 152 eyes; low-quality evidence). At 12 months post treatment, one trial reported that one of 51 eyes in the LASEK group lost one line or more best-spectacle corrected visual acuity compared with none of 51 eyes in the PRK group (RR 3.00, 95% CI 0.13 to 71.96; very low-quality evidence).Three trials reported adverse outcomes at 12 months of follow-up or longer. At 12 months post treatment, three trials reported corneal haze score; however, data were insufficient and were inconsistent among the trials, precluding meta-analysis. One trial reported little or no difference in corneal haze scores between groups; another trial reported that corneal haze scores were lower in the LASEK group than in the PRK group; and one trial did not report analyzable data to estimate a treatment effect. At 24 months post treatment, one trial reported a lower, but clinically unimportant, difference in corneal haze score for LASEK compared with PRK (MD -0.22, 95% CI -0.30 to -0.14; 184 eyes; low-quality evidence). AUTHORS' CONCLUSIONS: Uncertainty surrounds differences in efficacy, accuracy, safety, and adverse effects between LASEK and PRK for eyes with low to moderate myopia. Future trials comparing LASEK versus PRK should follow reporting standards and follow correct analysis. Trial investigators should expand enrollment criteria to include participants with high myopia and should evaluate visual acuity, refraction, epithelial healing time, pain scores, and adverse events.

[Efficacy observation of 0.1% bromfenac sodium eye drops on relieving the post-LASEK irritative symptoms].

OBJECTIVE: To observe the efficacy of bromfenac sodium eye drops on relieving the irritative symptoms after LASEK surgery. METHODS: Sixty-four people who had received LASEK surgery were randomly divided into two groups, observing the right eye for each group. group A was given 0.1% bromfenac sodium eye drops twice a day in three days before surgery and one day after surgery; group B was given 0.5% ketorolac tromethamine (acular) eye drops four times a day in three days before surgery and on day after surgery. In the 1(st), 3(rd), 5(th) and 7(th) day after surgery, irritative symptoms grade, duration of irritation, time for corneal epithelial healing, and uncorrected visual acuity were observed and compared between the two groups. RESULTS: 0.1% no discomfort in group A with bromfenac sodium eye drops was observed while 0.5% ketorolac tromethamine eye drops caused tingling, burning discomfort that lasted for 2-3 seconds in 16 of the 28 subjects (87.5%). No significant difference was observed between the irritation grades of group A and B (Z = -1.625, P = 0.104); the duration of irritative symptom was significantly shorter in group A than that in group B (Z = -2.895, P = 0.004) . No significant difference was observed between the time of healing and visual acuity recovery of the two groups. CONCLUSION: 0.1% bromfenac sodium eye drops can effectively relieve the post-LASEK irritative symptoms, and it is better tolerated than 0.5% ketorolac tromethamine eye drops.

The Unevenness and Non-orthogonal State of Distribution of Corneal Thickness and the Influence on Correction of Myopic Astigmatism by LASEK.

To observe and calculate the unevenness and the non-orthogonal state of distribution of corneal thickness and the relationship between them using Pentacam and to investigate the influence of unevenness and the non-orthogonal state on correction of myopic astigmatism by laser subepithelial keratomileusis (LASEK). 230 eyes with myopic astigmatism treated with LASEK were divided into two groups: 114 eyes as the low astigmatism group (-0.25 to -0.75 DC) and 116 eyes as the midrange-high astigmatism group (-1.00 to -4.50 DC). With the help of the diagram of keratoconus evaluation program of the Pentacam, the D 3.0 and D 6.5 were calculated for the index of distribution of unevenness of the corneal thickness, and the absolute value of the angle between the maximum and minimum progression-index orientation (M 90) for the index of non-orthogonal states. The correction of myopic astigmatism by LASEK was based on standard vector analysis and power vector analysis. The follow-up period was for 3 months. The preoperative M 90 was 22.14° ± 20.87°, D 6.5 was 58.66 ± 21.32 µm, and D 3.0 was 16.11 ± 4.28 µm for the 230 eyes that were tested. The D 6.5 of low astigmatism group (55.62 ± 20.81) µm was significantly lower than that of midrange-high astigmatism group (61.65 ± 21.48) µm (P < 0.05). Of the 230 eyes, the M 90 was positively correlated with D 6.5 (r = 0.37, P < 0.001), and D 6.5 was positively correlated with D 3.0 (r = 0.56, P < 0.001). 3 months postoperatively, the absolute error vector (|EV|) of low astigmatism group (0.46 ± 0.34) was significantly lower than that of midrange-high astigmatism group (0.53 ± 0.29) (P < 0.01). The error of magnitude of low astigmatism group (-0.10 ± 0.31) was significantly lower than that of midrange-high astigmatism group (0.08 ± 0.41) (P < 0.001). The absolute error of angle (|EA|) of low astigmatism group (26.10 ± 27.24) was significantly higher than that of midrange-high astigmatism group (9.99 ± 17.32) (P < 0.001). The correction ratio of low astigmatism group (1.45 ± 1.21) was significantly higher than that of midrange-high astigmatism group (0.94 ± 0.33) (P < 0.01). The error ratio (ER) of low astigmatism group (1.34 ± 1.40) was significantly higher than that of midrange-high astigmatism group (0.42 ± 0.27) (P < 0.001). In low astigmatism group, M 90 was positively correlated with |EV| (r = 0.30, P < 0.001). In midrange-high astigmatism group, M 90 was positively correlated with ER (r = 0.31, P < 0.001) and D 6.5 was positively correlated with |EV| and B, respectively (r = 0.34, 0.33, P < 0.001). The relationship between unevenness and non-orthogonal state of distribution of corneal thickness could influence the correction of astigmatism by LASEK. Therefore, more attention should be paid to the correction of midrange-high astigmatism group by excimer surgery.

Higher order aberrations of the corneal surface after laser subepithelial keratomileusis.

PURPOSE: To evaluate the changes of higher order aberrations (HOAs) before and after laser subepithelial keratomileusis (LASEK) and to analyze the influence of tear film instability on HOAs of the corneal surface after LASEK. METHODS: In this cross-sectional study, 31 patients who underwent LASEK were divided into dry eye (16 patients, 32 eyes) and non-dry eye groups (15 patients, 30 eyes). Uncorrected distance visual acuity, spherical equivalent refraction, ablation depth, tear film parameters and Ocular Surface Disease Index (OSDI) questionnaire scores were evaluated in both groups. Total HOA root mean square (RMS), third-order coma, third-order trefoil and fourth-order spherical aberration (SA) of the corneal surface immediately and at 10 seconds after blinking were measured before and after surgery. RESULTS: The total HOA RMS, coma, trefoil and SA significantly increased after LASEK compared with preoperative values in both groups. In the dry eye group, total HOA RMS, coma and trefoil significantly increased except for SA at 10 seconds after blinking compared with those measured immediately after blinking. In addition, the changes of total HOA RMS, coma and trefoil were negatively correlated with tear film break-up time (R = -0.420, -0.473 and -0.439, respectively), but positively correlated with OSDI score (R = 0.433, 0.499 and 0.532, respectively). In the non-dry eye group, there were no significant differences between HOAs measured at 10 seconds after blinking and those measured immediately after blinking. CONCLUSIONS: The HOAs including coma, trefoil and SA significantly increased after LASEK. The tear film instability in the dry eye can be associated with more deterioration of the optical quality after LASEK, due to more significant increase of total HOA RMS, coma and trefoil.

[The role of changes in the subfractional compound of tear fluid in the assessment of damaging effect from soft contact lenses and the excimer laser ablation of the cornea].

The method of laser correlation spectroscopy (LCS) was used for the examination of the subfractional compound of tear fluid in patients who have been using soft contact lens (SCL) for a long period and before and after the excimer laser correction with transepithelial photorefractive keratectomy (Trans PRK). Based on the analysis of biological material of 141 patients aged from 18 to 33 years old, we can conclude that prolonged usage of SCL leads to catabolic processes in surface of the anterior segment of the eye and, as a result, to changes in the qualitative composition of the tear fluid. The amount of low molecular weight fractions and medium weight ingredients increases after transepithelial photorefractive keratectomy, which can characterize reparation processes after cornea ablation. Based on the results of our study we can conclude that LCS--is express analysis, with which we can diagnose and observe the initial changes in local metabolism in the anterior segment of the eye, when the objective breaches have not seen yet.

Comparison of postoperative pain following laser-assisted subepithelial keratectomy and transepithelial photorefractive keratectomy: a prospective, random paired bilateral eye study.

PURPOSE: To compare postoperative pain following laser-assisted subepithelial keratectomy (LASEK) and transepithelial photorefractive keratectomy (T-PRK, two-step surgery) and alleviate postoperative subjective pain. METHODS: Thirty patients (60 eyes) with myopia or myopic astigmatism were consecutively recruited into this prospective, randomized paired study. Patients underwent LASEK in one eye, and T-PRK in the other. The degree of pain was rated on a scale of 0-10 on postoperative days 1, 2 and 3. Uncorrected visual acuity (UCVA) and subepithelial corneal haze were assessed at postoperative 1 and 3 months. RESULTS: The pain was relieved on the 4th postoperative day in all patients, healing of corneal epithelium was observed at 4-5 days after surgery and contact lenses were removed promptly. At postoperative 1 day, the mean subjective pain score in the LASEK group was 3.2 ± 1.88 and 4.43 ± 1.61 in T-PRK group (P = 0.008). No significant difference was found between two groups on postoperative 2 and 3 days. At postoperative 3 months, the percentage of UCVA ≥ 0.8 in the LASEK group was 100% and 96.7% in the T-PRK group (P = 0.24), 93.3% of patients in the LASEK with UCVA ≥ 1.0 and 90% in the T-PRK group (P = 0.64). In the LASEK group, the value of corneal haze was 0.26 ± 0.21 and 0.27 ± 0.25 in the T-PRK group (P = 0.877). CONCLUSION: Good visual acuity was obtained in both groups at postoperative 3 months. Compared with those in the T-PRK group, patients undergoing had less discomfort in the LASEK group, which may be associated with corneal epithelial activity. The changing curve of subjective pain in the T-PRK group was relatively flat and stable at postoperative 3 days.

Higher Order Aberrations of the Corneal Surface after Laser Subepithelial Keratomileusis

PURPOSE: To evaluate the changes of higher order aberrations (HOAs) before and after laser subepithelial keratomileusis (LASEK) and to analyze the influence of tear film instability on HOAs of the corneal surface after LASEK. METHODS: In this cross-sectional study, 31 patients who underwent LASEK were divided into dry eye (16 patients, 32 eyes) and non-dry eye groups (15 patients, 30 eyes). Uncorrected distance visual acuity, spherical equivalent refraction, ablation depth, tear film parameters and Ocular Surface Disease Index (OSDI) questionnaire scores were evaluated in both groups. Total HOA root mean square (RMS), third-order coma, third-order trefoil and fourth-order spherical aberration (SA) of the corneal surface immediately and at 10 seconds after blinking were measured before and after surgery. RESULTS: The total HOA RMS, coma, trefoil and SA significantly increased after LASEK compared with preoperative values in both groups. In the dry eye group, total HOA RMS, coma and trefoil significantly increased except for SA at 10 seconds after blinking compared with those measured immediately after blinking. In addition, the changes of total HOA RMS, coma and trefoil were negatively correlated with tear film break-up time (R = -0.420, -0.473 and -0.439, respectively), but positively correlated with OSDI score (R = 0.433, 0.499 and 0.532, respectively). In the non-dry eye group, there were no significant differences between HOAs measured at 10 seconds after blinking and those measured immediately after blinking. CONCLUSIONS: The HOAs including coma, trefoil and SA significantly increased after LASEK. The tear film instability in the dry eye can be associated with more deterioration of the optical quality after LASEK, due to more significant increase of total HOA RMS, coma and trefoil.

Pterygium after hyperopic laser-assisted sub-epithelial keratomileusis (LASEK).

A 61-year-old Caucasian woman with hyperopia presented for laser refractive surgery. She had healthy eyes with the exception of a less than 0.5 mm Salzmann's nodule at 5 o'clock near the limbus of the right eye. She underwent bilateral hyperopic laser-assisted sub-epithelial keratomileusis (LASEK) combined with removal of the Salzmann's nodule. At six months, she was emmetropic with unaided vision of 6/6; however, at 10 months, she noticed a reduction of acuity in her right eye and was found to have a pterygium at 5 o'clock, encroaching 3.5 mm onto the corneal surface. She underwent excision biopsy, local application of mitomycin-C (0.2 mg/ml for two minutes) and conjunctival auto-grafting. Following surgery for the pterygium, vision returned to 6/6 unaided but six months later, there was limited recurrence (1.5 mm) of the pterygium reducing unaided vision to 6/9, due to the induction of astigmatism of -1.25 dioptres. This has remained stable for 14 months. Pterygium growth may be associated with surface excimer laser surgery and the presence of peripheral Salzmann's nodules might be a risk factor.

Influence of Stiles-Crawford effect on visual performance after laser in situ keratomileusis.

We evaluated the impact of the Stiles-Crawford effect (SCE) on visual performance following laser in situ keratomileusis procedures. This prospective study included 71 eyes of 36 consecutive myopic patients (mean age, 20.94±3.69 years). Ocular aberrations and contrast sensitivity were measured one month after surgery. The SCE was modeled optically as a filter placed in front of the eye, and then the modulation transfer functions (MTFs) and the predicted log contrast sensitivity were calculated from the measured wavefront aberration data. Then the visual Strehl ratio for MTF (VSMTF) was calculated. The results indicated that the computed MTF with SCE were superior to that without SCE. The predicted contrast sensitivity functions were underestimated about 20% when the SCE was not taken into account for the scotopic pupil. Moreover, the measured contrast sensitivity was not significantly different from that with SCE at 6, 12, and 18 cycles/deg spatial frequencies. According to the obtained VSMTF ratio, optical qualities of all eyes were underestimated with the range from 5% (0.02 log unit) to 65% (0.22 log unit) without SCE, and the average value is 41% (0.15 log unit). When only taking higher-order aberrations into account, the predicted postoperative visual performance would be different from the real values. The evaluation of postoperative visual performance from wavefront aberrations should consider not only the compensation relationship between defocus and spherical aberration but also the SCE.

Ascorbate prophylaxis with mitomycin-C for corneal haze after laser-assisted sub-epithelial keratectomy.

BACKGROUND: Corneal haze is a significant complication of photorefractive keratectomy (PRK) and laser-assisted subepithelial keratectomy (LASEK). OBJECTIVES: To evaluate the effect of ascorbic acid supplementation in addition to perioperative topical mitomycin-C for the prevention of haze after LASEK. METHODS: We performed a retrospective, non-randomized case series study of two groups of 48 consecutive patients (96 myopic eyes) who had LASEK surgery. The treatment group was given ascorbic acid (vitamin C) orally, 500 mg, twice daily from 1 week before to 2 weeks after surgery. The control group was not offered any additional treatment. Ascorbate supplementation was the only difference in the postoperative treatment protocol between the treatment and control groups. Haze was assessed on a scale from 0 to 4 at the 1 year visit. RESULTS: Overall, 33.3% and 37.5% of the patients in the treatment and control groups respectively developed corneal haze. The trend of increased haze severity in the control group did not reach statistical significance. CONCLUSIONS: Our results showed that systemic ascorbate supplementation does not have an additional effect on the prevention of haze after LASEK compared to the effect of topical mitomycin-C alone.

Retrospective analysis of changes in the anterior corneal surface after Q value guided LASIK and LASEK in high myopic astigmatism for 3 years.

BACKGROUND: To compare the corneal high-order aberrations (HOAs), asphericity and regularity after Q-value guided laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) in high myopic astigmatism. METHODS: In this retrospectively comparative study, we measured the corneal HOAs, asphericity indices (Q values) and corneal regularity indices preoperatively and 36 months postoperatively in 70 eyes (35 patients) with Q-value guided surgeries. All the patients with high myopic astigmatism were divided into two groups which included 34 eyes underwent LASIK and 36 eyes underwent LASEK procedures. The main impact factors of the high-order aberrations were also analyzed. RESULTS: In the two groups, the efficacy index was more than 1.00 and safety index approached 1.00 at year 3 postoperatively. Statistically significant (P < 0.05) increased in Q values and main corneal HOAs (spherical aberrations and coma) following Q-value guided LASIK and LASEK procedures. Spherical aberrations increased more in the LASEK group and there was statistically difference compared to the LASIK group (P < 0.05). LASEK had better effects in correcting corneal astigmatism (P < 0.05). All the corneal regularity indices after surgeries increased and there was no significant difference (P = 0.707, P = 0.8 and P = 0.224, respectively) between the two groups. The main impact factors of spherical aberration included the optic zone size, changes of Q value, surgical procedure and the corrected refraction. CONCLUSIONS: In high myopic astigmatism, Q-value guided ablation showed good safety, efficacy and predictability. Q value, regularity indices, spherical aberration and coma increased in both LASIK and LASEK procedures. Astigmatism could be corrected more effectively by LASEK but greater spherical aberration could be created. The difference might be related to the different healing mechanisms. Optic zone size and the corrected refraction might be the main influence factors on the anterior corneal high order aberrations.