Femtosecond laser in laser in situ keratomileusis

Ray-Tracing Customization in Myopic and Myopic Astigmatism LASIK Treatments for Low and High Order Aberrations Treatment: 2-Year Visual Function and Psychometric Value Outcomes of a Consecutive Case Series

Purpose

The safety and long-term efficacy of automated ray-tracing customized myopic and myopic astigmatic femtosecond laser-assisted LASIK.

Methods

This consecutive case series retrospective analysis, of 20 subjects (40 eyes) treated with automated raytracing named Wavelight Plus, to include low and high order aberrations based on a three-dimensional custom virtual eye for each case-calculated from interferometry data-obtained from a single diagnostic device that also provides Hartman-Shack Wavefront and Scheimpflug tomography data. We evaluated before and after the customized LASIK procedure: visual acuity, refractive error, high order aberrations, contrast sensitivity, and psychometric post-operative visual function data.

Results

At 24 months, the comparison of the pre-operative to the post-operative refractive and visual function value changes in average were: subjective manifest refraction from -4.38 ± 2.54 diopters (D) (range -9.75 to -1.25 D) to +0.11 ± 0.19 D; subjective manifest refractive astigmatism from -0.76 ± 0.91 D (range -2.75 to 0 D) to -0.13 ± 0.16 D, corneal astigmatism from -1.16 ± 0.64 D (range -0.2 to -2.8) to -0.47 ± 0.11 D. 65% of the eyes studied demonstrated an increase of at least one line of vision, while from the same group 38% demonstrated 2 lines of increase. High order aberrations, contrast sensitivity as well as the subjective psychometric input based on the VFQ-25 questionnaire demonstrated actual improvement.

Conclusion

This longer-term follow-up, single-arm retrospective consecutive case series documents LASIK treatment customization that appears to be safe and effective in the correction of myopia and myopic astigmatism. Markedly improved objective and subjective visual function post-operatively, underlying the potential importance of simultaneously attempting to correct high order aberrations and improving the spatial alignment of total, measured human eye optics.

Effect of corneal flap thickness on opaque bubble layer formation in Visumax FS-LASIK using GEE analysis

Introduction

This study aimed to investigate two types of corneal flap thickness on opaque bubble layer (OBL) formation in Visumax femtosecond laser-assisted stromal for situ keratomileusis (FS-LASIK).

Methods

This retrospective study analyzed 203 eyes of 103 patients (32 men and 71 women) who underwent Visumax FS-LASIK between January 2020 and June 2020, and according to corneal flap thickness, they were divided into the 100-μm group (64 eyes) and the 110-μm group (139 eyes). Anterior-segment examination revealed no abnormal findings. Preoperatively, intraocular pressure (IOP), central corneal thickness (CCT), residual stromal thickness (RST), spherical power, cylindrical power, flat keratometry (K1), steep keratometry (K2), and biomechanical parameters including deformation amplitude (DA) ratio, Integrated Radius, stiffness parameter at first applanation (SP-A1), and Ambrosio relational thickness to the horizontal profile (ARTh) were evaluated. Primary outcomes were the incidence of OBL formation in the two groups compared by the Chi-square test and the correlation between the incidence of OBL and the above preoperative data by Spearman's Rho test. Secondary outcomes were the comparisons corrected by the generalized estimating equation (GEE) model.

Results

The incidence of OBL formation in the 100-μm group was 59.4 %, which was higher than that in the 110-μm group (23.0 %) with a significant difference (χ2 = 25.635, P < 0.001). The thinner corneal flap thickness (r = -0.355, P < 0.001) and higher spherical power (r = -0.142, P < 0.05) correlated with OBL formation. Higher K1 (r = 0.217, P < 0.01) and K2 (r = 0.198, P < 0.01) also correlated with OBL formation. The results of the GEE correction analysis showed higher rates of OBL formation in the 100-μm group (odds ratio [OR] = 4.704, 95 % CI 1.681-13.161, P < 0.01).

Conclusions

OBL was more likely to occur with the 100-μm corneal flap than with the 110-μm corneal flap in Visumax FS-LASIK. The risk of OBL formation in the 100-μm group was 4.704 times higher than that in the 110-μm group.

Design and test of a rigid endomicroscopic system for multimodal imaging and femtosecond laser ablation

Significance

Conventional diagnosis of laryngeal cancer is normally made by a combination of endoscopic examination, a subsequent biopsy, and histopathology, but this requires several days and unnecessary biopsies can increase pathologist workload. Nonlinear imaging implemented through endoscopy can shorten this diagnosis time, and localize the margin of the cancerous area with high resolution.

Aim

Develop a rigid endomicroscope for the head and neck region, aiming for in-vivo multimodal imaging with a large field of view (FOV) and tissue ablation.

Approach

Three nonlinear imaging modalities, which are coherent anti-Stokes Raman scattering, two-photon excitation fluorescence, and second harmonic generation, as well as the single photon fluorescence of indocyanine green, are applied for multimodal endomicroscopic imaging. High-energy femtosecond laser pulses are transmitted for tissue ablation.

Results

This endomicroscopic system consists of two major parts, one is the rigid endomicroscopic tube 250 mm in length and 6 mm in diameter, and the other is the scan-head (10 × 12 × 6    cm 3 in size) for quasi-static scanning imaging. The final multimodal image accomplishes a maximum FOV up to 650    μ m , and a resolution of 1    μ m is achieved over 560    μ m FOV. The optics can easily guide sub-picosecond pulses for ablation.

Conclusions

The system exhibits large potential for helping real-time tissue diagnosis in surgery, by providing histological tissue information with a large FOV and high resolution, label-free. By guiding high-energy fs laser pulses, the system is even able to remove suspicious tissue areas, as has been shown for thin tissue sections in this study.

The creation of a corneal incision with a femtosecond laser

BACKGROUND: The cutting action of a femtosecond laser (FS-laser) on the corneal tissue is performed using a photodestructive effect. FS-laser technology is used in many different areas of corneal surgery, and studying this effect is an actual issue. AIM: To evaluate the surface of the corneal incision created by a FS-laser (experimental study). MATERIALS AND METHODS: 20 porcine eyes were divided into two groups (FS-laser and keratome). The corneal tissue surface in the area of contact between two lips of the incision was visualized by electron microscopy. RESULTS: In all cases, we received a full-thickness incisions through the cornea. Images obtained by electron microscopy showed regular surface, no signs of thermal or mechanical damage to the corneal structure. CONCLUSIONS: The FS-laser is used as a microscopic scalpel in surgery. The precision cutting process is performed by mechanical forces generated by photodestruction by expanding cavitation bubbles.

Femtosecond Laser-Assisted Ophthalmic Surgery: From Laser Fundamentals to Clinical Applications

Femtosecond laser (FSL) technology has created an evolution in ophthalmic surgery in the last few decades. With the advantage of high precision, accuracy, and safety, FSLs have helped surgeons overcome surgical limits in refractive surgery, corneal surgery, and cataract surgery. They also open new avenues in ophthalmic areas that are not yet explored. This review focuses on the fundamentals of FSLs, the advantages in interaction between FSLs and tissues, and typical clinical applications of FSLs in ophthalmology. With the rapid progress that has been made in the state of the art research on FSL technologies, their applications in ophthalmic surgery may soon undergo a booming development.

Mechanisms of corneal intrastromal laser dissection for refractive surgery: ultra-high-speed photographic investigation at up to 50 million frames per second

Every year, more than a million refractive eye surgeries using femtosecond lasers are performed but the intrastromal cutting process remains an area of development. We investigated the mechanisms of laser dissection in cornea by ultra-high-speed photography. We found that the intrastromal bubble forms multiple lobes along the elongated laser plasma and the overlying lobes expand along the corneal lamellae. Videography demonstrated that the cutting process relies on crack propagation in the stroma along the bubble lobes with the crack originating from the pre-existing bubble layer. These insights are important for further improvement of the cutting mechanisms in refractive surgery.

Corneal neuromediator profiles following laser refractive surgery

Laser refractive surgery is one of the most commonly performed procedures worldwide. In laser refractive surgery, Femtosecond Laser in Situ Keratomileusis and Refractive Lenticule Extraction have emerged as promising alternatives to microkeratome Laser in Situ Keratomileusis and Photorefractive Keratectomy. Following laser refractive surgery, the corneal nerves, epithelial and stromal cells release neuromediators, including neurotrophins, neuropeptides and neurotransmitters. Notably, nerve growth factor, substance P, calcitonin gene-related peptide and various cytokines are important mediators of neurogenic inflammation and corneal nerve regeneration. Alterations in neuromediator profiles and ocular surface parameters following laser refractive surgery are attributed to the surgical techniques and the severity of tissue insult induced. In this review, we will discuss the (1) Functions of neuromediators and their physiological and clinical significance; (2) Changes in the neuromediators following various laser refractive surgeries; (3) Correlation between neuromediators, ocular surface health and corneal nerve status; and (4) Future directions, including the use of neuromediators as potential biomarkers for ocular surface health following laser refractive surgery, and as adjuncts to aid in corneal regeneration after laser refractive surgery.

Laser refractive surgery in pregnant or breastfeeding patients

This systematic review reported the outcomes of laser corneal refractive surgery in pregnant or breastfeeding patients. This study was performed by searching in PubMed, Web of Science, and Scopus databases, on June 15, 2020. Included were 128 eyes from a total of 64 patients, with the mean maximum follow-up was 39.2 ± 36.14 months. Time from surgery to complication ranged from 1 to 67 months, with a mean value of 23.42 ± 22.23 months. Photorefractive keratectomy and laser in situ keratomileusis surgery seem to be stable procedures that are not modified during pregnancy and safe to complete during breastfeeding. Nevertheless, the lack of weight prospective research avoids having a greater certainty on this matter, and because of transitory nature of pregnancy and breastfeeding, it could still be contemplated that surgery risk outweigh the benefits. Additional investigation will be necessary to clarify these issues.

A Comparative Study of Laser In Situ Keratomileusis Flaps Created Using Single-Functional Versus Multifunctional Femtosecond Laser for Refractive Surgery

PURPOSE

To compare laser in situ keratomileusis flaps created at the programmed target thickness of 120 μm using the LenSx multifunctional and the FS200 single-functional femtosecond lasers as evaluated by anterior segment optical coherence tomography (AS-OCT).

METHODS

This was a prospective, comparative, consecutive, blinded, nonrandomized study. Patients with stable refraction for over a year were consecutively allocated to the LenSx group or the FS200 group (n = 66; 33 patients in each group). All the patients underwent refractive surgery in both eyes. Previous eye surgery, ocular pathology associated with refractive errors, pregnancy, breastfeeding, and use of medication that causes ocular adverse effects constituted the exclusion criteria. Corneal topography, corneal tomography, dilated fundoscopy, applanation tonometry, ultrasonic pachymetry, dynamic and static refraction, visual acuity, and AS-OCT were evaluated before and after surgery. AS-OCT flap thickness was measured at 20 points on each cornea.

RESULTS

In the LenSx group, AS-OCT flap thickness differed significantly from the target thickness at 2 of 20 points (mean differences of 2.106 and 1.803 μm). In the FS200 group, 6 of 20 measurements differed significantly (mean differences ranging from 1.121 to 2.121 μm). The 2 lasers were similarly successful in creating regular and uniform flaps. The agreement between the 2 blinded examiners regarding the AS-OCT flap thickness measurements was excellent (intraclass correlation coefficient >0.75) in both groups.

CONCLUSIONS

Both femtosecond lasers were safe and capable of creating highly reproducible, uniform, and regular flaps at the target preoperative thickness of 120 μm. The LenSx multifunctional femtosecond laser offers the advantage of allowing both cataract and corneal surgeries.

Measurement of the Intraocular Pressure Elevation During Laser-Assisted In Situ Keratomileusis Flap Creation Using a Femtosecond Laser Platform

Purpose

The purpose of this study was to measure the intraocular pressure (IOP) elevation during laser assisted in situ keratomileusis (LASIK) flap creation using the WaveLight FS200 femtosecond (FS) laser platform.

Methods

We conducted an ex vivo experimental study in an animal model. The WaveLight FS200 FS laser platform was used to perform the corneal LASIK flap in freshly enucleated porcine eyes. We measured the changes in IOP from the application of the suction ring (suctioning phase) through the creation of the lamellar corneal flap (cutting phase). The IOP was recorded using a manometric technique with direct cannulation to the anterior chamber.

Results

Nine freshly enucleated porcine eyes were included in the study. The mean baseline IOP before the procedure was 20.33 ± 5.9 mm Hg. The mean IOP increase over baseline IOP was 32.33 ± 11.3 mm Hg at the suctioning phase, and 38.22 ± 11.3 mm Hg at the cutting phase. The total surgical time needed to complete the procedure was 29.5 ± 4.4 seconds.

Conclusions

The WaveLight FS200 FS laser platform produces a low to moderate increase in IOP during LASIK flap creation.

Translational Relevance

The WaveLight FS200 is a safe FS laser platform because it induces a low to moderate IOP increase during LASIK flap creation.

Topography-Guided Femto-LASIK in Virgin Eyes: Treating Manifest versus Measured Astigmatism

Purpose

To assess the stability, safety, predictability, and efficacy of topography-guided myopic Femto-LASIK with two different treatment protocols.

Setting

Ebsar Eye center, Benha, Qalyopia, Egypt.

Design

Single-center, retrospective, COHORT control study.

Methods

A total of 330 eyes enrolled in the study in group A and 322 eyes enrolled in group B underwent uncomplicated primary bilateral topography-guided Femto-LASIK. Group A was treated with the subjective clinical refraction; however, group B was treated with the modified refraction according to ALCON protocol.

Results

The mean preoperative refractive spherical equivalent (MRSE) was −4.85±1.90D and −5.0±1.93D in group A and B, respectively (P = 0.86), and a cylinder of −0.95±0.80 D and −0.92±0.81D, respectively. At the 12 months’ postoperatively, the residual manifest SE within ± 0.5D was achieved by 82.86% of eyes in group A compared to 83.93% in group B. Of eyes, 92.06% had ≤0.5 astigmatism dioptre, while 100% of eyes had ≤1.0 astigmatism dioptre in group A (315 eyes); however, 91.80% of eyes had ≤0.5 astigmatism dioptre, while 100% of eyes had ≤1.0 astigmatism dioptre in group B.

Conclusion

Topographic modification of the magnitude and axis of astigmatism treated using ALCON protocol when different from the clinical refraction may offer good refractive outcomes when we apply the Alcon precalculation considerations.

Initial Outcomes with Customized Myopic LASIK, Guided by Automated Ray Tracing Optimization: A Novel Technique

Purpose

Safety and efficacy of a novel automated ray tracing optimization in customization of excimer ablation in myopic LASIK.

Methods

In a consecutive case series, 25 patients (50 eyes) undergoing femtosecond-laser-assisted myopic LASIK were evaluated. The novel, artificial-intelligence platform initially calculates the ablation profile based on a model eye for each case, based on interferometry axial length data. Low- and high-order aberration calculation is performed by raytracing based on wavefront and Scheimpflug tomography measurements, all from a single diagnostic device. Visual acuity, refractive error, keratometry, topography, high-order aberrations and contrast sensitivity were evaluated, over six months follow-up.

Results

Change from pre- to 6 months post-operative: mean refractive error improved from −5.06 ± 2.54 diopters (D) (range −8.0 to −0.50 D) to −0.11 ± 0.09 D (range −0.25 to + 0.25); refractive astigmatism from −1.07 ± 0.91 D (range −4.25 to 0 D) to −0.15 ± 0.04 D (range −0.25 to 0); and topographic astigmatism from −1.65 ± 0.85 D to −0.26 ± 0.11 D (range −0.60 to 0). About 65% of eyes gained one line of vision and 38% 2 lines. Pre- to post-operative high-order aberration average: RMSh changed from 0.25 um to 0.35 um. Contrast sensitivity improved post-operatively.

Conclusion

We report safe and effective preliminary outcomes with a novel excimer laser customization by ray tracing optimization, for myopic LASIK treatments, employing several independent up-till-now diagnostics and a customized eye model reference for each case. It bears the potential advantage through total eye aberration data and ray tracing refraction calculation to offer improved and more predictable visual outcomes.

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Laser-assisted in-situ keratomileusis (LASIK) with a mechanical microkeratome compared to LASIK with a femtosecond laser for LASIK in adults with myopia or myopic astigmatism

BACKGROUND

Laser-assisted in-situ keratomileusis (LASIK) is a surgical procedure that corrects refractive errors. This technique creates a flap of the outermost parts of the cornea (epithelium, bowman layer, and anterior stroma) to expose the middle part of the cornea (stromal bed) and reshape it with excimer laser using photoablation. The flaps can be created by a mechanical microkeratome or a femtosecond laser.

OBJECTIVES

To compare the effectiveness and safety of mechanical microkeratome versus femtosecond laser in LASIK for adults with myopia.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2019, Issue 2); Ovid MEDLINE; Embase; PubMed; LILACS; ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We used no date or language restrictions. We searched the reference lists of included trials. We searched the electronic databases on 22 February 2019.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of LASIK with a mechanical microkeratome compared to a femtosecond laser in people aged 18 years or older with more than 0.5 diopters of myopia or myopic astigmatism.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 16 records from 11 trials enrolling 943 adults (1691 eyes) with spherical or spherocylindrical myopia, who were suitable candidates for LASIK. Five hundred and forty-seven participants (824 eyes) received LASIK with a mechanical microkeratome and 588 participants (867 eyes) with a femtosecond laser. Each trial included between nine and 360 participants. In six trials, the same participants received both interventions. Overall, the trials were at an uncertain risk of bias for most domains. At 12 months, data from one trial (42 eyes) indicates no difference in the mean uncorrected visual acuity (logMAR scale) between LASIK with a mechanical microkeratome and LASIK with a femtosecond laser (mean difference (MD) -0.01, 95% confidence interval (CI) -0.06 to 0.04; low-certainty evidence). Similar findings were observed at 12 months after surgery, regarding participants achieving 0.5 diopters within target refraction (risk ratio (RR) 0.97, 95% CI 0.85 to 1.11; 1 trial, 79 eyes; low-certainty evidence) as well as mean spherical equivalent of the refractive error 12 months after surgery (MD 0.09, 95% CI -0.01 to 0.19; 3 trials, 168 eyes [92 participants]; low-certainty evidence). Based on data from three trials (134 eyes, 66 participants), mechanical microkeratome was associated with lower risk of diffuse lamellar keratitis compared with femtosecond laser (RR 0.27, 95% CI 0.10 to 0.78; low-certainty evidence). Thus, diffuse lamellar keratitis was a more common adverse event with femtosecond laser than with mechanical microkeratome, decreasing from an assumed rate of 209 per 1000 people in the femtosecond laser group to 56 per 1000 people in the mechanical microkeratome group. Data from one trial (183 eyes, 183 participants) indicates that dry eye as an adverse event may be more common with mechanical microkeratome than with femtosecond laser, increasing from an assumed rate of 80 per 1000 people in the femtosecond laser group to 457 per 1000 people in the mechanical microkeratome group (RR 5.74, 95% CI 2.92 to 11.29; low-certainty evidence). There was no evidence of a difference between the two groups for corneal haze (RR 0.33, 95% CI 0.01 to 7.96; 1 trial, 43 eyes) and epithelial ingrowth (RR 1.04, 95% CI 0.11 to 9.42; 2 trials, 102 eyes [50 participants]). The certainty of evidence for both outcomes was very low.

AUTHORS' CONCLUSIONS

Regarding the visual acuity outcomes, there may be no difference between LASIK with mechanical microkeratome and LASIK with femtosecond laser. Dry eye and diffuse lamellar keratitis are likely adverse events with mechanical microkeratome and femtosecond laser, respectively. The evidence is uncertain regarding corneal haze and epithelial ingrowth as adverse events of each intervention. The limited number of outcomes reported in the included trials, some with potentially significant risk of bias, makes it difficult to draw a firm conclusion regarding the effectiveness and safety of the interventions investigated in this review.

Femtosecond laser induced step-like structures inside transparent hydrogel due to laser induced threshold reduction

In the area of laser material processing, versatile applications for cutting glasses and transparent polymers exist. However, parasitic effects such as the creation of step-like structures appear when laser cutting inside a transparent material. To date, these structures were only described empirically. This work establishes the physical and chemical mechanisms behind the observed effects and describes the influence of process and material parameters onto the creation of step-like structures in hydrogel, Dihydroxyethylmethacrylat (HEMA). By focusing laser pulses in HEMA, reduced pulse separation distance below 50 nm and rise in pulse energy enhances the creation of unintended step-like structures. Spatial resolved Raman-spectroscopy was used to measure the laser induced chemical modification, which results into a reduced breakdown threshold. The reduction in threshold influences the position of optical breakdown for the succeeding laser pulses and consequently leads to the step-like structures. Additionally, the experimental findings were supplemented with numerical simulations of the influence of reduced damage threshold onto the position of optical breakdown.

In summary, chemical material change was defined as cause of the step-like structures. Furthermore, the parameters to avoid these structures were identified.

Femtosecond laser in refractive corneal surgery

The introduction of the femtosecond (fs) laser has revolutionized ophthalmic surgery. With the worldwide application of fs-lasers, clinical outcomes and safety in corneal procedures have improved significantly and they have become an ideal tool for ultra-precise corneal refractive surgery. Flap creation in laser in situ keratomileusis (LASIK) is the most common use of this laser. It can also be used for other corneal refractive procedures including channel creation for the insertion of intrastromal corneal ring segments (ICRS), performing astigmatic keratotomies (AK), femtosecond lenticule extraction including small incision lenticule extraction (SMILE), and the insertion of corneal inlays. This article summarizes recent advanced applications of fs laser technology in corneal refractive surgery.

Comparison of Laser In Situ Keratomileusis Flap Morphology and Predictability by WaveLight FS200 Femtosecond Laser and Moria Microkeratome: An Anterior Segment Optical Coherence Tomography Study

PURPOSE

To evaluate laser in situ keratomileusis (LASIK) flap thickness predictability and morphology by femtosecond (FS) laser and microkeratome (MK) using anterior segment optical coherence tomography.

METHODS

Fifty-two candidates for the LASIK procedure were stratified into two groups: FS laser-assisted (Allegretto FS-200) and MK flap creation (Moria 2). Flap thickness was determined at five points. The side-cut angle was measured in three directions at the margin interface. LASIK flap assessment was performed one month postoperatively by Spectralis anterior segment optical coherence tomography.

RESULTS

Fifty-two patients (93 eyes) were recruited; 49 eyes were stratified to the FS group and 44 eyes to the MK group. The FS group had relatively even flap configurations, and the MK group had meniscus-shaped flaps. Mean differences between planned and actual flap thickness were 12.93 ± 8.89 and 19.91 ± 5.77 μm in the FS and MK groups, respectively. In thin flaps (100 to 110 μm), there was a significant disparity between the two groups (7.80 ± 4.71 and 19.44 ± 4.46 μm in the FS and MK groups, respectively). However, in thicker flaps (130 μm), comparable flap thickness disparity was achieved (18.54 ± 9.52 and 20.83 ± 5.99 μm in the FS and MK groups, respectively). Mean side-cut angle was 74.29 ± 5.79 degrees and 32.34 ± 4.94 degrees in the FS and MK groups, respectively.

CONCLUSIONS

Comparable flap thickness predictability was achieved in thicker flaps (130 μm), while the FS laser technique yielded a more predictable result in thinner flaps (100 to 110 μm). Different flap morphology was observed in meniscus flaps in MK-LASIK and flap morphology in FS-LASIK.

Comparative Analysis of LASIK Flap Diameter and its Centration Using Two Different Femtosecond Lasers

The aim of this study was to compare the diameter, accuracy, variability, and centration with respect to the limbus of corneal flaps created by two femtosecond lasers, the VisuMax, and Wavelight FS200, for laser in situ keratomileusis (LASIK) and how these flaps affect visual outcomes. This is a retrospective chart review of flap morphology created during LASIK Surgery. Overall, 168 eyes underwent flap creation using the WaveLight FS200 laser, and on 189 eyes, the VisuMax laser was used. Of these total number, flap morphology was analyzed in a random sample of 158 eyes; 80 with the Visumax laser and 78 with the WaveLight FS200 laser. Intraoperative photos of the flaps taken by the Wavelight Allegretto EX500 were analyzed. Flap diameters and centration were measured using Adobe Acrobat Pro. All patients had visual acuity measurements including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent refraction (SE) and refractive astigmatism recorded three months postoperatively. Greater than 90% of patients in both groups achieved a UDVA of 20/20 postoperatively. The mean difference between targeted and achieved flap diameter was 0.50 +/- 0.15 mm in the VisuMax group and 0.35 +/- 0.15 millimeters (mm) in the FS200 group (P<0.01). The flap diameters of the VisuMax group were more precise with a variance of 0.024 mm compared to a variance of 0.038 mm in the FS200 group (P<0.05). VisuMax flaps were more nasally displaced (log(N_A/T_A) = -0.21 +/- 0.10 mm) compared to the FS200 flaps (log(N_A/T_A) = 0.03 +/- 0.10 mm), (P< 0.01). We concluded that both the VisuMax and FS200 created flaps larger than the preoperative targeted diameter. VisuMax created corneal flaps that had a greater degree of deviation from the targeted diameter when compared to flaps from the FS200. However, there was less variance in the VisuMax flap diameter. In addition, VisuMax flaps were more nasally displaced. There were no statistically significant differences in visual outcomes when comparing the two femtosecond lasers.

Comparison Between Q-Adjusted LASIK and Small-Incision Lenticule Extraction for Correction of Myopia and Myopic Astigmatism

PURPOSE

To compare Q-adjusted femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and small-incision lenticule extraction (SMILE) in terms of safety, efficacy, and predictability, as well as in terms of changes in dry eye parameters, corneal biomechanics, higher-order aberrations (HOAs), and corneal asphericity.

METHODS

A total of 60 eyes were enrolled in this prospective comparative study: 30 underwent SMILE and 30 underwent FS-LASIK. Changes in manifest refraction, uncorrected distance visual acuity and corrected distance visual acuity, corneal topography, corneal hysteresis (CH), and corneal resistance factor (CRF) (Ocular Response Analyzer, ORA), and dry eye parameters were evaluated during a 3-month follow-up.

RESULTS

Mean manifest refraction spherical equivalent (MRSE) was -4.17 (±1.86) preoperatively in FS-SMILE group and -3.97 (±2.02) in FS-LASIK group (P=0.69). Mean postoperative MRSE in FS-SMILE group was -0.25±0.38 diopter (D) and -0.183±0.33 D in FS-SMILE group (P=0.50). A total of 93% of treated eyes in both groups had a MRSE within ±0.5 D. The mean percentage change of CH was 14.23±17.59 and 18.89±7.2 mm Hg (P=0.1871) in FS-SMILE and FS-LASIK groups, respectively. The mean percentage change of CRF was 27.43±16.8 and 21.32±17.1 mm Hg (P=0.1682) in FS-SMILE and FS-LASIK groups, respectively. A statistically significant difference between techniques were found in the values of Schirmer test (P=0.0002) and tear breakup time (P=0.0035). Regarding corneal HOAs, no statistically significant differences between groups were found in the change in the root mean square of HOAs (P=0.2), coma aberration (P=0.0589), and spherical aberration (P=0.0543).

CONCLUSION

SMILE is as safe and predictable as FS-LASIK. According to the ORA system, SMILE is not better than FS-LASIK in terms of biomechanical changes. However, SMILE causes less effect on dry eye parameters during the first 3 postoperative months.

Effects of femtosecond laser-assisted cataract surgery on dry eye

The aim of this study was to investigate the effect of femtosecond laser-assisted cataract surgery (FLACS) on tear film and ocular surface function. Patients with age-related cataract who underwent phacoemulsification (phaco) in Air Force Aviation Medicine Research Institute Affiliation Hospital from January 2016 to December 2016 were randomly divided into two groups. Patients in experimental group (n=123, 150 eyes) received FLACS, while patients in phaco group (n=110, 150 eyes) underwent conventional coaxial micro-incision phaco and were implanted with foldable intraocular lens (IOL). Our results showed that there were no statistically significant differences in general conditions between the two groups. Ocular surface disease index (OSDI) and corneal fluorescein staining (CFS) scores of patients in both groups after operation were significantly increased compared with those before operation, but breakup time (BUT) and Schirmer's I test scores decreased significantly at 1 week after operation compared with those before operation and basically returned to preoperative baseline levels at 3 months after operation. CFS scores and OSDI in the FLACS group at 1 day and 1 week after operation were increased more significantly than those in the phaco group, but there were no statistically significant differences at 3 months after operation. The above results showed that the effect on ocular surface function in the FLACS group after operation was greater than that in the phaco group, and the dry eye symptoms in the FLACS group were more obvious after operation. Both FLACS and conventional phaco have certain effects on the ocular surface function of patients, and there are statistically significant differences only in the early stage. FLACS has greater effects on CFS and dry eye symptoms.

Outcomes of LASIK for Myopia or Myopic Astigmatism Correction with the FS200 Femtosecond Laser and EX500 Excimer Laser Platform

Purpose:

To evaluate the efficacy, predictability, stability and safety of laser in situ keratomileusis (LASIK) using the FS200 femtosecond laser and EX500 excimer laser platform.

Methods:

The outcomes of 254 eyes of 129 consecutive patients with myopia or myopic astigmatism who underwent full correction femtosecond laser-assisted LASIK at CMU LASIK Center were assessed. Pre-operative and post-operative parameters including manifest refraction, Uncorrected Distance Visual Acuity (UDVA), Best Corrected Distance Visual Acuity (BDVA), corneal topography and tomography were analyzed. The results between low to moderate myopia and high myopia were compared up to 12 months.

Results:

Mean pre-operative Spherical Equivalent (SE) was -5.15±2.41 Diopters (D) (range -0.50 to -11.50 D) and -0.13±0.28 D, -0.13±0.27 D, -0.13±0.28 D and -0.14±0.30 D at 1, 3, 6, and 12 months, post-operatively. At 12 months, the propor¬tion of eyes achieving UDVA ≥ 20/20 was 90.0% and ≥20/40 was 98.8%. The proportion of eyes achieving post-operative mean SE ±0.5 D, and ±1 D was 91.3%, and 98.5%. No eyes lost more than two lines of BDVA. The low to moderate myopic group had a statistically significant better UDVA at one (p=0.017) and three months (p=0.014) but no difference at six (p=0.061) and 12 months (p=0.091). The mean post-operative SE was better in low to moderate myopic group at every follow-up visit (p=0.001, 0.007, <0.001 and <0.001).

Conclusion:

One-year clinical results of LASIK with the FS200 femtosecond laser and EX500 excimer laser showed high efficacy, predictability, stability and safety.

Femto-second laser (FSL) techniques and consistency in corneal surgery: experimental study

OBJECTIVE

To investigate the feasibility, effectiveness, and reproducibility of femtosecond laser (FSL) technology in different corneal cuts.

DESIGN

Experimental study at the Brandon Regional Health Centre.

PARTICIPANTS

Twenty two Human Cadaver eyes donated for research and supplied by the eye bank of Manitoba university.

METHODS

In this experimental study, the effectiveness and reproducibility of FSL were investigated in different corneal cuts. The corneas were divided into 5 groups: group I for penetrating keratoplasty; group II for anterior lamellar keratoplasty; group III for corneal pockets for inlays; group IV for intracorneal ring tunnels; and group V for corneal cross-linking pockets. Our primary endpoint was the repeatability of planned versus obtained thickness and diameter of the cuts with FSL. A secondary endpoint was the effectiveness and ease of dissection, rated from 0-4, with 4 being the easiest and 0 the most difficult to dissect.

RESULTS

There was a high correlation between planned and obtained thickness (r = 0.997, p < 0.001) and diameter (r = 0.998, p < 0.001). Both were statistically significant. Linear regression analyses showed that the obtained thickness of corneal cuts in micrometers was significantly predicted by the planned thickness of corneal cuts in micrometers (β = 0.996, t = 56.47, p < 0.001). Likewise, the obtained diameter of corneal cuts in millimeters was significantly predicted by the planned diameter of corneal cuts in millimeters (β = 0.971, t = 70.85, p < 0.001). The surgeons gave 15 out of a total of 22 corneas (68.2%) the maximum score for ease of dissection (Grade 4), where no adhesions were found and the dissection was smooth and steady. Five corneas out of a total of 22 (22.7%) were given a score of 3 of 4 where minor adhesions were found. Two corneas out of a total of 22 (9.1%) were given a score of 2 of 4 where >1 adhesion was found, with some difficulty in separating the cut cornea from the bed. No corneas were given grade 1 or grade 0. No significant differences were obtained for the ease of dissection among the 5 surgery types using Kruskal-Wallis H test (H [4] = 4.971, p > 0.05).

CONCLUSION

The measured corneal-cut geometry correlated well with laser settings in a variety of full- and partial-thickness FSL corneal patterns, including different depths and diameters. This reproducible efficacy and measurement accuracy of the planned versus obtained cuts could have a favourable result on a variety of corneal surgeries. It also yields a favourable ease of dissection of the cut lenticule from the stromal bed.

High incidence of rainbow glare after femtosecond laser assisted-LASIK using the upgraded FS200 femtosecond laser

Background

To compare the incidence of rainbow glare (RG) after femtosecond laser assisted-LASIK (FS-LASIK) using the upgraded FS200 femtosecond laser with different flap cut parameter settings.

Methods

A consecutive series of 129 patients (255 eyes) who underwent FS-LASIK for correcting myopia and/or astigmatism using upgraded WaveLight FS200 femtosecond laser with the original settings was included in group A. Another consecutive series of 129 patients (255 eyes) who underwent FS-LASIK using upgraded WaveLight FS200 femtosecond laser with flap cut parameter settings changed (decreased pulse energy, spot and line separation) was included in group B. The incidence and fading time of RG, confocal microscopic image and postoperative clinical results were compared between the two groups.

Results

There were no differences between the two groups in age, baseline refraction, excimer laser ablation depth, postoperative uncorrected visual acuity and refraction. The incidence rate of RG in group A (35/255, 13.73%) was significantly higher than that in group B (4/255, 1.57%) (P < 0.05). The median fading time was 3 months in group A and 1 month in group B (P > 0.05).The confocal microscopic images showed wider laser spot spacing in group A than group B. The incidence of RG was significantly correlated with age and grouping (P < 0.05).

Conclusions

The upgraded FS200 femtosecond laser with original flap cut parameter settings could increase the incidence of RG. The narrower grating size and lower pulse energy could ameliorate this side effect.

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.

Accuracy of Alcon WaveLight® EX500 optical pachymetry during LASIK

Purpose

To study the accuracy and reliability of optical pachymetry using the Alcon WaveLight EX500 during laser-assisted in situ keratomileusis (LASIK).

Materials and methods

This was a retrospective chart review of 90 eyes from 45 patients who had undergone LASIK (mean age 35.2±8.2 years; 19 males, 26 females). The WaveLight FS200 femtosecond laser was programmed to cut LASIK flaps at a desired depth of 120 μm. Optical low-coherence reflectometry (WaveLight EX500) was used to measure central corneal thickness prior to lifting the flap, and the residual stromal bed immediately after excimer ablation. Flap thickness (FT) was calculated using simple subtraction. Optical coherence tomography (OCT) was used to measure central corneal thickness, flap thickness, and residual stromal bed in the postoperative period and the results compared to intraoperative measurements.

Results

Mean programmed FS200 FT was 119 μm. Mean FT using EX500 optical pachymetry was 109 μm. The difference between FS200- programmed and EX500-measured FT was 9 μm (P<0.001). There was also a significant difference between the EX500 and OCT FT (109 μm vs 119 μm, respectively; P<0.001).

Conclusion

FT values calculated using intraoperative EX500 optical pachymetry were significantly lower than programmed FS200 values or OCT measurements.

Visumax femtolasik versus Moria M2 microkeratome in mild to moderate myopia: efficacy, safety, predictability, aberrometric changes and flap thickness predictability

Introduction

This is an interventional prospective clinical study which was conducted to evaluate the efficacy, safety, predictability, ocular aberrations, and flap thickness predictability of Visumax femtosecond laser (FSL) compared to Moria M2 microkeratome (MK) in mild to moderate myopia.

Methods

This study included 60 eyes who were divided into two groups. Thirty eyes in group (I) in which the flap was created with Visumax FSL, while in group II (30 eyes) the Moria M2 MK was used. Keratometric, refractive, and aberrometric measurements were compared preoperatively and 3 months postoperatively. The intraoperative subtraction pachymetry (the SP 100 Handy pachymeter (Tomey, Nagoya, Japan) was used for preoperative pachymetry and flap thickness measurement.

Results

No significant difference was found between the two groups in regards to postoperative manifest sphere, spherical equivalent, astigmatism, safety indices nor ocular aberrations. Twenty six eyes (86.6%) in group I and 23 eyes in group II (76.6%) were within ±0.5D of the intended correction and 23 eyes (76.6%) in group I and 15 eyes in group II (50%) were within ±0.25D of the intended correction. In group I, the mean postoperative actual flap thickness was 100.12 ± 16.1 μm (81 to 122 μm), while in group II, it was 104.6 ± 20.1 μm (62 to 155 μm). The difference was statistically significant (p = 0.001).

Conclusions

Both Visumax and Moria M2 MK are safe and effective in treating myopia with no statistically significant difference in induction of ocular aberrations but with potential advantage for Visumax regarding predictability. More accurate flap thickness is achieved with Visumax femtolasik.

Trial registration

This study was retrospectively registered on 19/6/2017. Trial registration number NCT03193411, clinicalTrials.gov.

OCT Study of the Femtosecond Laser Opaque Bubble Layer

PURPOSE

To characterize the location and regularity of the opaque bubble layer (OBL) in the corneal stroma after femtosecond laser-assisted LASIK (FS-LASIK) flap generation.

METHODS

In this prospective study, 30 eyes of 15 patients who had FS-LASIK surgery for myopia, astigmatism, and/or hyperopia were included. Screen captures were obtained at the end of the flap creation and the eyes with hard type OBL were immediately imaged with anterior segment optical coherence tomography.

RESULTS

The mean age of the 9 men and 6 women was 40 ± 11.3 years (range: 22 to 60 years). Seven eyes (23.3%) developed hard type OBL that was typically localized in the central cornea beneath the LASIK flap and, in the majority of cases, located close to the hinge of the flap. Three of the seven eyes had OBL only within the laser cut, whereas the four other eyes had OBL in a spotty distribution within the stromal bed beneath the flap. None of the eyes had an accumulation of OBL within the flap itself.

CONCLUSIONS

The excimer laser ablation of a stroma with OBL may be different from that of a stroma without OBL. Management of OBL when it occurs due to flap production, including allowing the bubble to dissipate when they overlie the pupil, is important to obtain the best outcomes with femtosecond laser-assisted LASIK. [J Refract Surg. 2017;33(1):18-22.].

[Evaluation of vision quality after laser vision correction in healthcare professionals]

PURPOSE

Healthcare professionals require good quality of vision. The main objective of this study is to evaluate the satisfaction and vision quality after laser vision correction in healthcare professionals.

METHODS

This is a monocentric retrospective study. An online 25-question survey was sent to ametropic physicians, surgeons and nurses who underwent corneal refractive surgery with laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) between July 2012 and February 2016. Questionnaire responses were recorded anonymously by the internet survey site. These patients' pre- and postoperative data were analyzed.

RESULTS

In total, 2491 laser vision corrections were performed during this time frame. One hundred and fifty-eight patients were healthcare providers; 131 received the survey, and 111 responded. Ninety-nine were surgeons, 60 were medical physicians, and 32 were nurses. Ninety-one percent reported that they were satisfied with their postoperative vision quality, 63.9% even reported an improvement in their quality of vision compared with their corrected preoperative vision, 92.8% reported that they would have the procedure again, and 94.6% would recommend the procedure to a family member or a patient. Visual outcomes showed high levels of efficacy and predictability.

CONCLUSION

While healthcare professionals require good quality of vision, those who had undergone laser vision correction reported the same satisfaction as the general population and would recommend the procedure to their family, friends and patients.

Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK

PURPOSE

To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies.

SETTING

Private clinical ophthalmology practice.

PATIENTS AND METHODS

A total of 100 eyes (50 patients) in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers) were randomized for treatment as follows: one eye with the standard clinical refraction (group A) and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B). All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), topography (Placido-disk based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months.

RESULTS

Mean refractive error was -5.5 D of myopia and -1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over -0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B (P<0.01). The residual percentages in both groups were measured with refractive astigmatism of more than -0.5 diopters.

CONCLUSION

Topography-modified refraction (TMR): topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings may change the current clinical paradigm of the optimal subjective refraction utilized in laser vision correction.

Vision-related quality of life and visual outcomes after small-incision lenticule extraction and laser in situ keratomileusis

PURPOSE

To compare vision-related quality of life (VRQoL) scores and clinical outcomes between small-incision lenticule extraction and laser in situ keratomileusis (LASIK).

SETTING

Singapore National Eye Centre, Singapore.

DESIGN

Prospective study.

METHODS

Patients had small-incision lenticule extraction using the Visumax 500 kHz femtosecond laser; or LASIK excimer ablation with the Wavelight Allegretto 400 Hz laser. Primary outcomes were 3-month predictability, efficacy, and safety. Secondary outcomes were intraoperative experience, visual symptoms, and VRQoL (validated Quality of Life Impact of Refractive Correction [QIRC] questionnaire) in 25 a subgroup of patients in each group. Following Rasch analysis, "Functional" and "Emotional," QIRC dimensions were analysed separately.

RESULTS

At 3 months, predictability (82.5% versus 85.3%, ±0.5 diopters attempted correction, P =.453), safety index (1.13 ± 0.19 [SD] versus 1.07 ± 0.16, P = .158), and efficacy index (0.91 ± 0.21 versus 0.97 ± 0.19; P = .002) were found when comparing small-incision lenticule extraction (172 eyes) and LASIK (matched 688 eyes). Intraoperative experience between groups was not statistically different; visual fluctuations (P = .020) and episodes of visual blurring (P = .008) were greater after small-incision lenticule extraction than after LASIK at 1 month but not at 3 months. There was no difference in "functional" (66.7 ± 15.7 versus 55.3 ± 22.2, P = .064) and "emotional" (42.7 ± 23.2 versus 37.9 ± 23.8, P = .394) QIRC dimensions between the 2 groups (25 patients in each group) at 3 months.

CONCLUSION

The study, 3-month predictability, safety, and VRQL scores were not statistically different between small-incision lenticule extraction and LASIK.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Comparison of Forward Light Scatter Changes Between SMILE, Femtosecond Laser-assisted LASIK, and Epipolis LASIK: Results of a 1-Year Prospective Study

PURPOSE

To investigate the characteristics of forward light scatter changes after small incision lenticule extraction (SMILE) and to compare these changes with those after femtosecond laser-assisted LASIK (femto-LASIK) and epipolis LASIK (epi-LASIK).

METHODS

A total of 303 eyes (SMILE group = 118 eyes, femto-LASIK group = 90 eyes, epi-LASIK group = 95) of 157 patients were included in this study. Forward straylight was measured preoperatively and 1 month, 6 months, and 1 year postoperatively using a C-Quant straylight meter (Oculus Optikgeräte, Wetzlar, Germany).

RESULTS

A significant increase in straylight was found in the femto-LASIK group only at 1 month after the procedure (P = .002), whereas significant increases were found in the epi-LASIK group at 1 month, 6 months, and 1 year after the procedure (P < .001). There were no significant increases in the straylight values after SMILE (P = .310) compared with the preoperative values, although the straylight values were slightly increased at 1 month. Significant differences in the postoperative-preoperative straylight value (Δlog[s]) changes were found between the SMILE, femto-LASIK, and epi-LASIK groups over the follow-up period (P < .001 for all). The correlations between the ablation depth/central corneal thickness ratios and the straylight values were statistically significant in the femto-LASIK and epi-LASIK groups, whereas no significant correlation between the lenticule thickness/central corneal thickness ratios and the stray-light values was found in the SMILE group.

CONCLUSIONS

Forward straylight was slightly increased in the early stage after the femto-LASIK procedure and was significantly increased throughout the follow-up period after epi-LASIK surgery. The SMILE procedure appeared to have a smaller effect on forward light scatter within the 1-year follow-up period.

Corneal tissue interactions of a new 345 nm ultraviolet femtosecond laser

PURPOSE

To assess the suitability of a new 345 nm ultraviolet (UV) femtosecond laser for refractive surgery.

SETTING

Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.

DESIGN

Experimental study.

METHODS

Twenty-five porcine corneas were used for stromal flap or lamellar bed creation (stromal depth, 150 μm) and 15 rabbit corneas for lamellar bed creation near the endothelium. Ultraviolet femtosecond laser cutting-line morphology, gas formation, and keratocyte death rate were evaluated using light and electron microscopy and compared with a standard infrared (IR) femtosecond laser. Endothelial cell survival was examined after application of a laser cut near the endothelium.

RESULTS

Flaps created by the UV laser were lifted easily. Gas formation was reduced 4.2-fold compared with the IR laser (P = .001). The keratocyte death rate near the interface was almost doubled; however, the death zone was confined to a region within 38 μm ± 10 (SD) along the cutting line. Histologically and ultrastructurally, a distinct and continuous cutting line was not found after UV femtosecond laser application if flap lifting was omitted and standard energy parameters were used. Instead, a regular pattern of vertical striations, presumably representing self-focusing induced regions of optical tissue breakdown, were identified. Lamellar bed creation with standard energy parameters 50 μm from the endothelium rendered the endothelial cells intact and viable.

CONCLUSION

The new 345 nm femtosecond laser is a candidate for pending in vivo trials and future high-precision flap creation, intrastromal lenticule extraction, and ultrathin Descemet-stripping endothelial keratoplasty.

FINANCIAL DISCLOSURES

Mr. Klenke and Ms. Skerl were paid employees of Wavelight GmbH when the study was performed. Dr. Seiler is a scientific consultant to Wavelight GmbH. No other author has a financial or proprietary interest in any material or method mentioned.

Postoperative ocular higher-order aberrations and contrast sensitivity: femtosecond lenticule extraction versus pseudo small-incision lenticule extraction

PURPOSE

To evaluate and compare changes in contrast sensitivity and ocular higher-order aberrations (HOAs) after femtosecond lenticule extraction (FLEx) and pseudo small-incision lenticule extraction (SMILE).

SETTING

Singapore National Eye Centre, Singapore.

DESIGN

Retrospective case series.

METHOD

Patients had femtosecond lenticule extraction (Group 1) or pseudo small-incision lenticule extraction (Group 2) between March 2010 and December 2011. The main outcome measures were manifest refraction, HOAs, and contrast sensitivity 1, 3, 6, and 12 months postoperatively.

RESULTS

Fifty-two consecutive patients (102 eyes) were recruited, 21 patients (42 eyes) in Group 1 and the 31 patients (60 eyes) in Group 2. The uncorrected and corrected distance visual acuities were significantly better in Group 2 than in Group 1 at 12 months (P = .032). There was no significant increase in 3rd- or 4th-order aberrations at 1 year and no significant difference between the 2 groups preoperatively or postoperatively. At 1 year, there was a significant increase in mesopic contrast sensitivity in Group 2 at 1.5 cycles per degree (cpd) (P = .008) that was not found in Group 1, and photopic contrast sensitivity at 6.0 cpd was higher in Group 2 (P = .027).

CONCLUSIONS

These results indicate that refractive lenticule extraction is safe and effective with no significant induction of HOAs or deterioration in contrast sensitivity at 1 year. Induction of HOAs was not significantly different between both variants of refractive lenticule extraction. However, there was significant improvement in photopic contrast sensitivity after pseudo small-incision lenticule extraction, which persisted through 1 year.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Safety of cornea and iris in ocular surgery with 355-nm lasers

A recent study showed that 355-nm nanosecond lasers cut cornea with similar precision to infrared femtosecond lasers. However, use of ultraviolet wavelength requires precise assessment of ocular safety to determine the range of possible ophthalmic applications. In this study, the 355-nm nanosecond laser was evaluated for corneal and iris damage in rabbit, porcine, and human donor eyes as determined by minimum visible lesion (MVL) observation, live/dead staining of the endothelium, and apoptosis assay. Single-pulse damage to the iris was evaluated on porcine eyes using live/dead staining. In live rabbits, the cumulative median effective dose (ED50) for corneal damage was 231 J/cm2, as seen by lesion observation. Appearance of endothelial damage in live/dead staining or apoptosis occurred at higher radiant exposure of 287 J/cm2. On enucleated rabbit and porcine corneas, ED50 was 87 and 52 J/cm2, respectively, by MVL, and 241 and 160 J/cm2 for endothelial damage. In human eyes, ED50 for MVL was 110 J/cm2 and endothelial damage at 453 J/cm2. Single-pulse iris damage occurred at ED 50 of 208 mJ/cm2. These values determine the energy permitted for surgical patterns and can guide development of ophthalmic laser systems. Lower damage threshold in corneas of enucleated eyes versus live rabbits is noted for future safety evaluation.

Refractive lenticule extraction: transition and comparison of 3 surgical techniques

PURPOSE

To describe the transition and outcomes of 3 refractive lenticule extraction (ReLEx) techniques: femtosecond lenticule extraction (FLEx), small-incision lenticule extraction (SMILE), and pseudo small-incision lenticule extraction.

SETTING

Singapore National Eye Center, Singapore.

DESIGN

Prospective comparative case series.

METHODS

Refractive lenticule extraction was performed between March 1, 2010, and November 1, 2012, using the Visumax 500 kHz femtosecond laser system. The main outcome measures were the refractive efficacy, predictability, and safety over 12 months.

RESULTS

The study enrolled 88 eyes. All 3 refractive lenticule extraction techniques yielded good refractive outcomes and stability over 12 months. Three months postoperatively, the mean overall efficacy index of refractive lenticule extraction was 0.89±0.22 (SD), with 95.5% of eyes attaining an uncorrected distance visual acuity (UDVA) of better than 20/40 and 60.2% of better than 20/20. Of all eyes, 95.5% were within ±1.00 diopter (D) and 78.4% within ±0.50 D of the attempted correction. The mean overall safety index was 1.06±0.17. At 3 months, all small-incision lenticule extraction eyes and 96.7% of pseudo small-incision lenticule extraction eyes had a UDVA of 20/40 or better, while femtosecond lenticule extraction eyes had a lower efficacy index (87.0%). However, efficacy was comparable in all 3 groups by 12 months (mean 0.87±0.04 [standard error of the mean]; P=1.00).

CONCLUSION

The efficacy, safety, and predictability profiles of the 3 refractive lenticule extraction techniques were good over a 12-month follow-up.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

The evolution of corneal and refractive surgery with the femtosecond laser

The use of femtosecond lasers has created an evolution in modern corneal and refractive surgery. With accuracy, safety, and repeatability, eye surgeons can utilize the femtosecond laser in almost all anterior refractive procedures; laser in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), penetrating keratoplasty (PKP), insertion of intracorneal ring segments, anterior and posterior lamellar keratoplasty (Deep anterior lamellar keratoplasty (DALK) and Descemet's stripping endothelial keratoplasty (DSEK)), insertion of corneal inlays and cataract surgery. As the technology matures, it will push surgical limits and open new avenues for ophthalmic intervention in areas not yet explored. As we witness the transition from femto-LASIK to femto-cataract surgery it becomes obvious that this innovation is here to stay. This article presents some of the most relevant advances of femtosecond lasers to modern corneal and refractive surgery.

Histological analysis of a cornea following experimental femtosecond laser ablation

Corneal photorefractive surgery is currently performed by ablation of corneal stroma under the stromal flap. A stromal flap is created using a femtosecond (FS) laser or mechanical microkeratome, although the FS laser procedure is considered safer and more accurate. This review assesses and compares the use of FS laser versus mechanical microkeratome ablation for corneal stromal characteristics mainly examined by histology and cellular biological responses. Supporting data from our studies, using corneas of enucleated porcine eye globes, are included in this review. Histological analysis and experimental studies of cellular/tissue responses to FS laser irradiation should be further investigated, and the equipment used to perform these techniques should be improved.

Complications of femtosecond-assisted laser in-situ keratomileusis flaps

Femtosecond-assisted laser in-situ keratomileusis flaps have revolutionized refractive surgery since their introduction. Although these lasers are exceedingly safe, complications still do occur. This review focuses specifically on examining the literature and evidence for flap complications during femtosecond-assisted laser in-situ keratomileusis as well as their management.

Femtosecond laser in refractive and cataract surgeries

In the past few years, 9 unique laser platforms have been brought to the market. As femtosecond (FS) laser-assisted ophthalmic surgery potentially improves patient safety and visual outcomes, this new technology indeed provides ophthalmologists a reliable new option. But this new technology also poses a range of new clinical and financial challenges for surgeons. We provide an overview of the evolution of FS laser technology for use in refractive and cataract surgeries. This review describes the available laser platforms and mainly focuses on discussing the development of ophthalmic surgery technologies.

Longitudinal comparison of outcomes after sub-Bowman keratomileusis and laser in situ keratomileusis: randomized, double-masked study

PURPOSE

To compare the outcomes of sub-Bowman keratomileusis (100-μm flap) and laser in situ keratomileusis (LASIK) (120-μm flap) using 150-kHz femtosecond laser.

DESIGN

Randomized, double-masked, contralateral clinical trial.

METHODS

One hundred patients (200 eyes) with myopia or myopic astigmatism were included. Postoperative examinations were performed at week 1 and months 1, 3, 6, and 12. Main outcome measures included postoperative uncorrected (UCVA) and best-corrected distance visual acuity (BCVA); manifest refraction spherical equivalent; efficacy and safety indices; corneal thickness; and complications.

RESULTS

The mean age of patients was 33.9 ± 7.9 years. Overall, the preoperative UCVA, BCVA, and manifest refraction spherical equivalent were 1.349 ± 0.332, -0.022 ± 0.033, and -5.81 ± 1.61 diopters, respectively. No significant difference was observed in preoperative (P ≥ .226) or intraoperative parameters (P ≥ .452) between both groups, except residual stromal thickness (P < .001). The UCVA, manifest refraction spherical equivalent, and central corneal thickness stabilized by 1 week, while the thinnest corneal thickness stabilized by 3 months postoperatively. There was no significant difference between both groups for any parameter during all follow-up visits (P ≥ .132) except the 3-month safety index, which was better in the sub-Bowman keratomileusis group (P = .007). Soft opaque bubble layer was noted intraoperatively in 12 cases (7, 100-μm group; 5, 120-μm group; P = .577). No postoperative complications were observed.

CONCLUSIONS

Our study did not find any differences in the visual and refractive outcomes between femtosecond-assisted sub-Bowman keratomileusis and LASIK. Both surgeries resulted in quick visual recovery as early as 1 week postoperatively.

Autologous Serum Eye Drops Accelerate Epithelial Healing After LASEK

PURPOSE

To evaluate the effect of autologous serum on the rate of epithelial healing and clinical results after laser epithelial keratectomy (LASEK) for correction of myopia.

MATERIALS AND METHODS

Thirty eyes of 15 patients received autologous serum drops (Study Group) while 30 eyes of 15 patients received conventional artificial tears (Control Group) after LASEK. LASEK was performed with 25-second application of 18% alcohol. Laser ablation was performed with the ESIRIS excimer laser (SCHWIND, Kleinostheim, Germany). Patients were seen daily until epithelial closure, and at 1, 3, 6, and 12 months. Time to epithelial healing was the main outcome measure. Uncorrected visual acuity (UCVA), manifest refraction, and haze were recorded.

RESULTS

Preoperative myopic spherical equivalent refraction was -2.98 ± 1.13 diopters (D) in the study group and -2.65 ± 1.01 D in the control group (p = 0.264). The mean time to epithelial healing was about 1 day shorter in the eyes receiving autologous serum than the eyes receiving conventional treatment (2.78 ± 0.40 days versus 3.73 ± 0.58 days, respectively) (p = 0.001). All eyes achieved 20/25 or better UCVA at 6 months. Over 90% of eyes were within ±0.50 D of emmetropia at 12 months in both groups. No significant difference was noted in the incidence of haze.

CONCLUSIONS

Autologous serum eye drops seem to accelerate epithelial healing after LASEK, which may shorten the duration of early postoperative discomfort by about 1 day.

Refractive and Aberration Outcomes after Customized Photorefractive Keratectomy in Comparison with Customized Femtosecond Laser

To compare the refractive and visual outcomes and higher order aberrations in patients with low to moderate myopia who underwent customized photorefractive keratectomy (PRK) or femtosecond laser in situ keratomileusis (Femto-LASIK) this research performed. This study includes data of 120 consecutive eyes of 60 patients with myopia between -3.00 D and -7.00 D with or without astigmatism in two surgery groups: PRK and Femto-LASIK. Refractive, visual, and aberration outcomes of the two methods of surgery were compared after 6 months of follow-up. After six months of follow-up, sphere and cylinder were found significantly decreased and there was no statistically significant difference between the two groups. The mean of uncorrected distance visual acuity in LogMar format for the PRK and Femto-LASIK groups was -0.03±0.07 and -0.01±0.08, respectively, which was not significantly different between the two groups. Higher orders and spherical aberrations increased in both groups significantly, while total aberrations decreased in both groups. After surgery, no differences were observed between the two groups in the amount of aberrations. In conclusion, Both PRK and Femto-LASIK are effective and safe in correcting myopia. In this study PRK induced more spherical and higher order aberrations than Femto-LASIK.