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Purpose: To analyse the effect of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) on the electrical response of retinal ganglion cells using pattern electroretinography (pERG)., Methods: This was a longitudinal, prospective, observational pilot study. We included consecutive myopic patients who underwent FS-LASIK to correct up to 6 dioptres of myopia and up to 2 dioptres of astigmatism. Patients with excessive blinking or tearing and those with Snellen uncorrected visual acuity less than 0.9 dec on postop day 1 were excluded. Diopsys NOVA ® (Diopsys Inc., NJ) pERG records, using high- and low-contrast patterns, were obtained 16 h and 1 month after FS-LASIK was performed. Magnitude (μV), Magnitude D (μV), Magnitude D/Magnitude ratio and signal-to-noise ratio (dB) were analysed. Wilcoxon test for nonparametric paired data was employed., Results: pERG data from 24 eyes were analysed from 24 patients who underwent FS-LASIK. Mean age was 35.79 ± 9.86 years. Mean preoperative refraction was -2.69 ± 7.6 D (spherical) and -0.38 ± 0.40 D (cylinder). Mean surgical time was 56.88 ± 7.6 s. No statistically significant differences were obtained for any of the studied parameters when comparing 16 h with 1 month after FS-LASIK, with the exception of Magnitude with low contrast, which increased from 1.21 ± 0.2 to 1.39 ± 0.29 µV at 16 h and 1 month postoperatively, respectively ( p  = 0.03)., Conclusions: FS-LASIK seems to induce a mild and transitory defect in retinal ganglion cell function. Only a mild decrease was detected in the magnitude value for low-contrast stimuli when pERG was performed 16 h postoperatively, and it returned to normal 1 month after surgery.

Introduction: Higher preoperative myopic astigmatism is associated with a higher probability of retreatment due to patient dissatisfaction as a result of residual cylindrical error. Nonetheless, retreatment is safe and the final clinical results are comparable to those of patients with lower preoperative astigmatism who were satisfied with the primary treatment. Our purpose is to compare the efficacy and safety of femtosecond LASIK (FS-LASIK) for the refractive correction of patients with low (< 1.5 Diopters (D) versus high (≥ 1.5 D) myopic astigmatism., Methods: Retrospective observational study of 841 eyes of 825 eligible patients treated with FSLASIK for the correction of simple or compound myopic astigmatism. Outcome measures included residual error, best corrected and uncorrected distance visual acuity (BCVA and UCVA), efficacy and safety 3 months after the primary procedure or the retreatment., Results: Of 841 eyes in total, 432 (51.37%) had < 1.5 D (Group 1) and 409 (48.63%) had ≥ 1.5 D (Group 2) preoperative myopic astigmatism. The efficacy index of primary treatment was 0.94 ± 0.18 in Group 1 and 0.89 ± 0.22 in Group 2 (P = 0.001). Of 138 eyes (16.41%) that were retreated due to dis-satisfaction related to residual refractive error, 28 belonged to Group 1 (6.5%) and 110 (26.9%) to Group 2 (P < 0.001). Following retreatment, small but statistically significant differences in the residual mean postoperative cylinder (-0.08 ± 0.24 vs -0.27 ± 0.46 D, P = 0.001) and UCVA (1.11 vs 0.96, P = 0.0001) were detected for Groups 1 and 2, respectively. However, there were no statistically significant differences in the safety and efficacy indices., Conclusion: Following FS-LASIK, eyes with myopic astigmatism ≥ 1.5 D have approximately four times more chances of undergoing retreatment due to dis-satisfaction caused by residual refractive error compared to eyes with myopic astigmatism < 1.5 D. However, the clinical results after retreatment are highly satisfactory and comparable in both groups., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

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., Competing Interests: Conflict of Interest Disclosure: None of the authors have reported a financial conflict of interest., (Copyright © 2021 American Academy of Optometry.)

Purpose: To describe the postoperative evolution of visual acuity, flap morphology, and stromal optical density femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK)., Setting: Clínica Rementería, Madrid, Spain., Design: Prospective case series., Methods: The study comprised 44 consecutive eyes that had FS-LASIK performed with the WaveLight FS200 and the Allegretto excimer laser to correct myopia. Visual outcomes, flap thickness, and stromal optical density were assessed 1 day, 1 week, 1 month, and 3 months postoperatively., Results: A statistically significant improvement in the mean uncorrected distance visual acuity at 1 day (0.94 ± 0.2) and 1 week (0.93 ± 0.2) to 1 month (1.04 ± 0.2) and 3 months (1.11 ± 0.1) postoperatively (P < .05). At 3 months postoperatively, the femtosecond laser had good outcomes in efficacy (0.98 ± 0.1), safety (0.98 ± 0.1), and predictability (100% of eyes were within ± 0.5 D of emmetropia). The femtosecond-created flaps were slightly thicker than intended, the mean SD intraflap was 7.1 μm, the range between the thickest and thinnest points in each flap was 25.4 μm, and the mean flap thickness homogeneity was 7.6 μm at 3 months postoperatively. A progressive decrease in the optical density of the flap stroma and the residual stromal bed was detected during follow-up., Conclusions: The femtosecond laser study appears to be a safe, effective, and predictable platform to obtain LASIK flaps. The flaps were planar and homogeneous but slightly thicker than intended. The optical density of the flap stroma was slightly higher at early follow-up and decreased over time.

Purpose: To describe and compare the stromal bed roughness obtained after laser in situ keratomileusis (LASIK) flap creation using a corneal femtosecond laser platform (iFS 150) and a "dual" femtosecond (FS) laser platform (LenSx)., Methods: This ex vivo experimental study was conducted in an animal model using 12 freshly enucleated porcine eyes, six with each femtosecond laser. The standard laser treatment parameters were used for the experiment. After LASIK flap creation, the corneal stromal roughness was assessed using atomic force microscopy (AFM) in contact mode immersed in liquid. In each sample, surface measurements were obtained in 60 regions of six eyes per FS laser in 10 20 × 20-micron areas of the central corneal stroma at 512 × 512-point resolution. The surface roughness was measured and the root-mean-square (RMS) values of the roughness were obtained., Results: The mean RMS ± standard deviation values were 430 ± 150 nm for the corneal femtosecond laser platform and 370 ± 100 nm for the dual FS laser platform (P < 0.011)., Conclusions: In this experimental study with AFM, we found smoother stromal beds after LASIK flap creation with LenSx compared to iFS 150 kHz. Further studies are needed to understand visual implications of the differences found.

Purpose: To analyze the recovery of the subbasal nerve plexus in corneas treated with laser in situ keratomileusis (LASIK) at least 10 years prior compared with nonoperated corneas., Setting: Clínica Novovisión, Madrid, Spain., Design: Prospective nonrandomized observational study., Methods: Eyes that had LASIK surgery at least 10 years before (LASIK group) were compared with nonoperated healthy eyes (control group). The subbasal nerve plexus morphology (main nerves density, nerve length, nerve branches density, grade of nerve tortuosity, and reflectivity) and the dendritic cell density from the confocal images obtained with the Heidelberg Retina Tomograph II were analyzed., Results: The study comprised 47 eyes (27 eyes in the LASIK group and 20 eyes in the control group). The values were significantly lower in the LASIK group compared with the control group in main nerves density (9.15 nerves/mm 2  ± 3.46 [SD] versus 11.75 ± 2.86 nerves/mm 2 ; P = .009) and nerve branches density (2.96 ± 1.99 nerves/mm 2 versus 5.35 ± 3.05 nerves/mm 2 ; P = .002). No significant differences were found in nerve length, grade of nerve tortuosity, dendritic cell density, or subbasal nerve plexus reflectivity between the two groups., Conclusions: The outcomes suggested that the subbasal corneal nerve plexus did not completely recover its preoperative pattern at least 10 years after LASIK. Both main nerves density and nerve branches density continued to be significantly lower compared with virgin corneas after a mean 13-year follow-up, although other parameters of nerve morphology (nerve length, tortuosity, and reflectivity) returned to normal levels., (Copyright © 2019 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2019 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.)

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., (Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.)

Purpose: To compare the 3-month postoperative refractive results and flap thickness homogeneity after correction of myopia using the Intralase femtosecond platform and the Victus dual femtosecond laser platform., Setting: Novovision Clinic, Madrid, Spain., Design: Prospective case series., Methods: Eyes treated with a 60 kHz femtosecond laser (Group 1) and eyes treated with a dual femtosecond laser (Group 2) were included. The refractive results 3 months postoperatively were compared. The differences between the maximum and the minimum thickness point of each flap, the intraflap standard deviation (SD), and the achieved and the targeted central flap thickness were evaluated in each group., Results: The study comprised 31 eyes in Group 1 and 20 eyes in Group 2. Three months postoperatively, the uncorrected distance visual acuity, residual refraction, efficacy, safety, and predictability were significantly better in Group 1. The dual femtosecond laser induced a significantly greater increase in higher-order aberrations than the conventional femtosecond laser. The mean central flap thickness was 123.2 μm ± 9.2 (SD) in Group 1 and 116.3 ± 14.4 μm in Group 2 (P = .005). The mean difference between the maximum and the minimum flap thickness points in each flap was significantly lower in Group 1 than in Group 2 (22 ± 8.3 μm versus 35.7 ± 16.9 μm) (P = .0007). The intraflap SD was significantly lower in Group 1 than in Group 2 (6.1 μm versus 10.8 μm) (P = .0001)., Conclusion: The conventional femtosecond laser provided better efficacy, safety, predictability, and flap thickness homogeneity than the dual femtosecond laser for the correction of myopia., (Copyright © 2018 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

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.]., (Copyright 2017, SLACK Incorporated.)