Comparing high and low energy outcomes on day one for SmartSight myopic-astigmatism treatments with the SCHWIND ATOS: a retrospective case series.

BACKGROUND: Impact of low energy asymmetric spacings vs. high energy symmetric spacings on the immediate/early (postoperative day 1 (POD1)) outcomes of SmartSight lenticule extraction for myopic astigmatism with a new femtosecond laser system. METHODS: The first 112 eyes of 56 patients consecutively treated using low energy asymmetric spacings (Group A; Study group) were compared at POD1 to the last 112 eyes of 56 patients consecutively treated using high energy symmetric spacings (Group S; Controls). Mean age of the patients was 28 ± 5 years with a mean spherical equivalent of -4.41 ± 1.76 diopters (D) and a mean magnitude of refractive astigmatism of 0.89 ± 0.82 D. RESULTS: Laser Energy was -25 ± 1nJ lower for asymmetric treatments (p < .0001); Spot and Track distances were + 0.7 ± 0.1 µm larger and -0.8 ± 0.1 µm tighter for asymmetric treatments, respectively (p < .0001 for both). At POD1, astigmatism was -0.08 ± 0.02D lower for asymmetric treatments (p < .0003); uncorrected and corrected visual acuities (UDVA and CDVA, respectively) were -0.03 ± 0.01logMAR better for asymmetric treatments (p < .0007); differences between postop UDVA and preop CDVA along with change in CDVA were + 0.3 ± 0.1lines better for asymmetric treatments (p < .0003). CONCLUSIONS: Lenticule extraction treatment using SmartSight is safe and efficacious already at POD1. Findings suggest that low energy asymmetric spacings may further improve the immediate and short-term outcomes of SmartSight lenticule extraction in the treatment of myopic astigmatism compared to conventional settings (high energy symmetric spacings).

Symmetric offset versus asymmetric offset ablation with transepithelial refractive keratectomy.

BACKGROUND: In eyes with hyperopia, astigmatism, and mixed astigmatism Transepithelial photorefractive keratectomy (TransPRK) is a modality of surface ablation surgery. We center on the corneal vertex for all our treatments (all have an offset to the center of the pupil) and wanted to compare the visual results of symmetrical profile treatments versus asymmetrical profile treatments (the center of the treatment on the vertex and the boundaries with the pupil center) using TransPRK as corneal refractive surgery. METHODS: We retrospectively analyzed two consecutive groups of eyes treated with TransPRK in the Aurelios Augenlaserzentrum Recklinghausen: 47 eyes treated with symmetrical offset and 51 eyes treated with asymmetrical offset. The intergroup comparisons were assessed using unpaired Student's T-tests, whereas preoperative to postoperative changes were assessed using paired Student's T-tests. RESULTS: Refractive outcomes were good for both groups. 83 and 88% of eyes were within the spherical equivalent of 0.5 D from the target in the symmetric and asymmetric offset groups, respectively. 85 and 84% of eyes had a postoperative astigmatism of 0.5 D or lower in the symmetric and asymmetric offset groups, respectively. CONCLUSION: We have not found a significant difference in the refractive outcomes between the symmetric group and the asymmetric group of eyes treated both with TransPRK for preoperatively hyperopic or mixed astigmatism.

Analysis of Impact of Humidity and Temperature on Excimer Laser Ablation of Polyethylene Terephthalate, Polymethylmethacrylate, and Porcine Corneal Tissue.

BACKGROUND AND OBJECTIVES: To analyze the impact of humidity and temperature on excimer laser ablation of polyethylene terephthalate (PET), polymethylmethacrylate (PMMA) and porcine corneal tissue, and an ablation model to compensate for the temperature and humidity changes on ablation efficiency. STUDY DESIGN/MATERIALS AND METHODS: The study was conducted using an AMARIS 1050RS (Schwind eye-tech-solutions) placed inside a climate chamber at ACTS. Ablations were performed on PET, PMMA, and porcine cornea. The impact of a wide range of temperature (~18°C to ~30°C) and relative humidity (~25% to ~80%) on laser ablation outcomes was tested using nine climate test settings. For porcine eyes, change in defocus was calculated from the difference of post-ablation to pre-ablation average keratometry readings. Laser scanning deflectometry was performed to measure refractive change achieved in PMMA. Multiple linear regression was performed using the least square method with predictive factors: temperature, relative humidity, time stamp. Influence of climate settings was modeled for pulse energy, pulse fluence, ablation efficiency on PMMA and porcine cornea tissue. RESULTS: Temperature changes did not affect laser pulse energy, pulse fluence (PET), and ablation efficiency (on PMMA or porcine corneal tissue) significantly. Changes in relative humidity were critical and significantly affected laser pulse energy, high fluence and low fluence. The opposite trend was observed between the ablation performance on PMMA and porcine cornea. CONCLUSIONS: The proposed well-fitting multi-linear model can be utilized for compensation of temperature and humidity changes on ablation efficiency. Based on this model, a working window for optimum operation has been found (temperature 18°C to 28°C and relative humidity 25% to 65%) for a maximum deviation of ±2.5% in ablation efficiency in PMMA and porcine corneal tissue. Lasers Surg. Med. © 2019 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Comparison between Wavefront-optimized and corneal Wavefront-guided Transepithelial photorefractive keratectomy in moderate to high astigmatism.

BACKGROUND: To compare the clinical outcomes of wavefront-optimized (WFO) transepithelial photorefractive keratectomy (trans-PRK) and corneal wavefront-guided (CWFG) trans-PRK for myopic eyes with moderate to high astigmatism. METHODS: One hundred ninety-six eyes (196 patients) with moderate to high astigmatism (≥ 1.75 D) treated with WFO or CWFG trans-PRK (101 and 95 eyes, respectively) were retrospectively registered. Safety, efficacy, predictability, vector analysis, and corneal aberrations were compared between groups preoperatively and at 6 months postoperatively. RESULTS: At postoperative 6 months, the mean logMAR uncorrected distance visual acuity was similar in the WFO (- 0.07 ± 0.08) and CWFG (- 0.07 ± 0.07) groups. Safety, efficacy, and predictability of refractive and visual outcomes were also similar. The correction indices were 1.02 ± 0.14 and 1.03 ± 0.13 in the WFO and CWFG groups, respectively, with no significant difference. The absolute values of the angle of error were significantly higher in the WFO group (2.28 ± 2.44 vs. 1.40 ± 1.40; P = 0.002). Corneal total root mean square higher-order aberrations and corneal spherical aberrations increased postoperatively in both groups; however, the change was smaller in the CWFG group. Corneal coma showed a significant increase postoperatively only in the WFO group. CONCLUSIONS: WFO and CWFG trans-PRK are safe and effective for correcting moderate to high astigmatism. However, CWFG trans-PRK provides a more predictable astigmatism correction axis and fewer induced corneal aberrations.

Nonwavefront-guided Presby reversal treatment targeting a monofocal cornea after bi-aspheric ablation profile in a patient intolerant to multifocality.

PURPOSE: To analyze distance and near vision after a nonwavefront-guided Presby reversal treatment targeting a monofocal cornea in a patient intolerant to multifocality in the dominant eye. METHODS: Case report. RESULTS: An originally myopic patient treated for correcting distance ametropia and simultaneously alleviating presbyopic symptoms resulted in intolerance to the induced multifocality. Twenty-one months after the bi-aspheric multifocal treatment, the patient was treated with PresbyMAX reversal (SCHWIND eye-tech-solutions, Kleinostheim, Germany) to remove the previously induced multifocality. Original corrected distance visual acuity (CDVA) was -0.1 logMAR (20/16 Snellen) with +0.8 logMAR (J12) uncorrected near visual acuity (UNVA) and changed to CDVA +0.1 logMAR (20/25 Snellen) with +0.2 logMAR (J4) UNVA before the Presby reversal procedure (all monocularly). Three months after the reversal treatment, uncorrected distance visual acuity and CDVA were both -0.1 logMAR (20/16 Snellen), and the patient was emmetropic and had no further visual complaint for distance, but at the cost of losing the UNVA. CONCLUSIONS: Nonwavefront-guided Presby reversal treatments targeting a monofocal cornea after bi-aspheric ablation profile were successful.

Determination of the excimer laser ablation rate in previously cross-linked corneas.

PURPOSE: To evaluate the need for and quantify the extent of nomogram adjustments to compensate for potential changes in the amount of effective corneal stroma ablated in previously cross-linked corneas. METHODS: Ex vivo porcine corneas were divided into two groups (the corneal cross-linking [CXL] group, n = 30; and the control group, n = 3): these experimental corneas underwent CXL including deepithelialization, instillation of riboflavin solution for 25 minutes, and ultraviolet-A irradiation at 9 mW/cm2 for 10 minutes. The control group was deepithelialized only. Four consecutive excimer laser ablations of 50 pm each were performed (AMARIS 750S; SCHWIND eye-tech-solutions, Kleinostheim Germany), and stromal bed thickness was measured with a built-in optical coherence pachymeter. To determine the potential influence of riboflavin, a third group (the riboflavin group, n = 12) underwent deepithelialization and instillation of riboflavin, but no ultraviolet-A irradiation. RESULTS: The mean individual ablation depth across the four ablations was significantly smaller in cross-linked corneas (-17%) when compared to untreated control corneas (P < .001). A consistent reduction of 12% was observed via a cumulative analysis when assessing the relative isolated effect of CXL on the ablation rate. There was no significant effect from riboflavin in the deeper ablations, except for the first ablation (68.6 + 1.1 mm [range: 1 to 50 pm]). This may be due to a measurement error in pachymetric readings due to the thin film of riboflavin on the surface that resists even extensive rinsing. CONCLUSIONS: CXL reduces the corneal ablation depth of excimer lasers in the anterior 200 pm of the porcine cornea by approximately 12%. Further clinical studies are needed to validate these findings in human corneas.

Clinical History Method versus Corneal Tomographers in Estimating Corneal Power after Photorefractive Surgery

AIMS: To investigate the concordance between the corneal power determined by various approaches with two tomographers (MS-39® and Galilei G6®) and the clinical history method (CHM) in patients undergoing photorefractive surgery with excimer laser for myopic errors. MATERIAL AND METHODS: Prospective cohort study. Patients undergoing keratorefractive surgery, and having pre- and postoperative keratometries, and tomographies, were included. RESULTS: In 90 eyes, the differences in the power estimated by the CHM and the one determined by four approaches with the corneal tomographers, which included measurements of the posterior cornea, did not show statistically significant differences in their averages. However, the 95% limits of agreement were very wide. After obtaining regression formulas to adjust the values of these four variables, the results of the agreement analysis were similar. CONCLUSION: Although certain values either directly determined or derived from measurements with the Galilei® and MS-39®corneal tomographers, approximated the estimated value of postoperative corneal power according to the CHM, due to the amplitude of their limits of agreement, these calculations must be taken with care, because they may not be accurate in a given eye.

Risk Factors for Re-treatment After Keratorefractive Lenticule Extraction (KLEx) for Myopia and Myopic Astigmatism.

PURPOSE: To identify potential risk factors that increase the likelihood of re-treatment following keratorefractive lenticule extraction (KLEx) for myopia and myopic astigmatism. METHODS: This was a retrospective study of patients with myopia and myopic astigmatism who underwent KLEx using the VisuMax 500 laser (Carl Zeiss Meditec) between April 2015 and December 2020. Patients were assigned to one of two groups: the control group and the re-treatment group (if they had additional refractive surgery within 2 years of the primary treatment). The effect of different preoperative, intraoperative, and postoperative parameters on the re-treatment rate was analyzed. RESULTS: Overall 1,822 eyes of 938 patients were analyzed. In total, 2.96% of eyes (n = 54) underwent re-treatment. The re-treated patients were more likely to be women and have high myopia, high astigmatism, steep corneas, higher ocular residual astigmatism, and residual myopic and/or astigmatic refractive error. In contrast, no significant correlation was found between re-treatment rate and age, chord µ, type of astigmatism, and corneal thickness. CONCLUSIONS: Factors associated with higher rates of retreatment after KLEx included female gender, manifest refractive high myopia (> -5.00 diopters [D]), astigmatism (> 2.00 D), spherical equivalent (> 6.00 D), ocular residual astigmatism, steeper corneas, and postoperative residual myopic and astigmatic refractive errors. This study may help to preoperatively detect patients at risk for re-treatment, improve preoperative patient counseling, and optimize patient selection to reduce future re-treatment rates. [J Refract Surg. 2024;40(6):e362-e370.].

SmartSight Correction of Compound Myopic Astigmatism Treatments With Preoperative Astigmatism > 1.00 Diopter Using the SCHWIND ATOS: A Retrospective Case Series.

PURPOSE: To evaluate moderate to high astigmatism corrections on the outcomes of SmartSight lenticule extraction for myopic astigmatism with a new femtosecond laser system. METHODS: Two hundred ninety-two eyes consecutively treated for myopic astigmatism with astigmatism magnitude greater than 1.00 diopter (D) were evaluated at the 6-month follow-up visit. The mean age of the patients was 29 ± 6 years with a mean spherical equivalent of -5.06 ± 2.20 diopters (D) and a mean magnitude of refractive astigmatism of 1.74 ± 0.61 D. RESULTS: At 6 months, astigmatism was 0.10 ± 0.20 D. Uncorrected and corrected distance visual acuities (UDVA and CDVA, respectively) were both 0.0 ± 0.1 logMAR. Differences between postoperative UDVA and preoperative CDVA and the change in CDVA were both +0.4 ± 0.7 lines better than preoperatively (P < .0003). CONCLUSIONS: Lenticule extraction treatment using Smart-Sight is safe and efficacious at 6 months. Findings suggest that moderate to high astigmatism improves after SmartSight lenticule extraction in the treatment of myopic astigmatism. [J Refract Surg. 2024;40(5):e328-e335.].

Method to determine the centration of a lenticule of tissue extracted from a cornea.

A simple and novel method to analyse the centration of a lenticule of tissue extracted from a cornea has been developed, in which the centre of "mass" of the individual differences between post and preoperative maps of several corneal metrics represents the lenticule centration and its spatial distance to a reference point (aimed centration) determines the decentration. Different parameters have been evaluated to weight the centre of "mass". The robustness of the methods has been evaluated using perturbation analysis (adding white-noise to the data) based on realistic uncertainties. A clipped analysis has been performed to prevent large, localised areas of lacking/missing data from affecting the centre of "mass". The method has been tested on a pilot cohort of clinical data showing 30% and 63% of the treatments within 200 µm of decentration for corneal thickness and refractive equivalent power, respectively. Except for anterior elevation with a total standard deviation of 17 µm, all other metrics show excellent precision of ∼5 µm. The method provides a reliable and objective way to determine the centration of a lenticule of tissue extracted from a cornea and it can be applied to any topo- or tomographic derived metric.

Twelve-month outcomes of a new refractive lenticular extraction procedure.

BACKGROUND: To evaluate the 12-month refractive and visual outcomes of Small Incision Guided Human-cornea Treatment (SmartSight®, SCHWIND eye-tech-solutions, Kleinostheim, Germany) in the treatment of myopia corrections with low to moderate astigmatism with the use of a new femtosecond laser system. METHODS: 221 eyes of 114 patients consecutively treated with SmartSight lenticule extraction were assessed. The mean age of the patients was 28±6 years at the time of treatment with a mean spherical equivalent refraction of -6.26±2.17D and mean astigmatism of 0.92±0.68D. Monocular corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) were assessed pre- and post-operatively. Refractive changes have been determined in terms of changes in refraction, as well as changes in keratometric readings. The changes in central epithelial thickness have been determined. RESULTS: At twelve months post-operatively, mean UDVA was 20/21±2. Spherical equivalent showed a residual refraction of +0.48±0.31D with refractive astigmatism of 0.13±0.18D postoperatively. There was a slight decrease of -0.1 Snellen lines at 12-months follow-up. The same correction was determined using changes in refraction, as well as changes in keratometric readings. The central epithelial thickness increased by +3±2µm. Spherical equivalent correction within ±0.50D was achieved in 199 eyes (90%), and cylindrical correction in 221 (100%). Preoperative corrected distance visual acuity (CDVA) was 20/20 or better in 213 eyes (96%), and postoperative uncorrected (UDVA) was 20/20 or better in 205 eyes (93%). No eye had lost two or more Snellen lines of CDVA. CONCLUSIONS: Myopic astigmatism correction with SmartSight provided good results for efficacy, safety, predictability, and visual outcomes at the twelve months of follow up. The central epithelial thickness barely increased by 3±2µm.

Long-term results of hyperopic ablations using alcohol-assisted PRK and FS-LASIK: comparative study.

PURPOSE: To evaluate the long-term visual and refractive outcomes of hyperopic excimer ablation using alcohol-assisted photorefractive keratectomy (PRK) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). SETTING: American University of Beirut Medical Center, Beirut, Lebanon. DESIGN: Retrospective, matched comparative study. METHODS: Eyes that underwent alcohol-assisted PRK were compared to matched eyes that underwent FS-LASIK. All patients were followed up for at least 3 years after surgery. The refractive and visual outcomes of each group were compared at different postoperative time points. The main outcome measures were spherical equivalent deviation from target (SEDT), manifest refraction, and visual acuity. RESULTS: 83 eyes underwent alcohol-assisted PRK and 83 matched eyes underwent FS-LASIK. Preoperative manifest refraction spherical equivalent was 2.44 ± 1.18 diopters (D) and 2.20 ± 0.87 D ( P = .133) in the PRK and FS-LASIK groups, respectively. Preoperative manifest cylinder was -0.77 ± 0.89 D and -0.61 ± 0.59 D ( P = .175) for the PRK and LASIK groups, respectively. 3 years postoperatively, SEDT was 0.28 ± 0.66 D and 0.40 ± 0.56 D for the PRK and LASIK groups, respectively ( P = .222), whereas manifest cylinder was -0.55 ± 0.49 D and -0.30 ± 0.34 D for PRK and LASIK, respectively ( P < .001). The mean difference vector was 0.59 ± 0.46 for PRK and 0.38 ± 0.32 for LASIK ( P < .001). 13.3% of PRK eyes and 0% of LASIK eyes had >1 D of manifest cylinder ( P = .003). CONCLUSIONS: Both alcohol-assisted PRK and FS-LASIK are safe and effective for the treatment of hyperopia. PRK induces slightly more postoperative astigmatism than LASIK. Larger optical zones and recently introduced ablation profiles that lead to a smoother ablation surface might improve the clinical results of hyperopic PRK.

First European results of a new refractive lenticular extraction procedure-SmartSight by SCHWIND eye-tech-solutions.

BACKGROUND: To evaluate vision 3 months after SmartSight lenticule extraction treatments. DESIGN: Case series. METHODS: This case series of patients were treated at Specialty Eye Hospital Svjetlost in Zagreb, Croatia. Sixty eyes of 31 patients consecutively treated with SmartSight lenticule extraction were assessed. The mean age of the patients was 33 ± 6 years (range 23-45 years) at the time of treatment with a mean spherical equivalent refraction of -5.10 ± 1.35 D and mean astigmatism of 0.46 ± 0.36 D. Monocular corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) were assessed pre- and post-operatively. Ocular and corneal wavefront aberrations have been postoperatively compared to the preoperative baseline values. Changes in ocular wavefront refraction, as well as changes in keratometric readings are reported. RESULTS: At 3 months post-operatively, mean UDVA was 20/20 ± 2. Spherical equivalent showed a low myopic residual refraction of -0.37 ± 0.58 D with refractive astigmatism of 0.46 ± 0.26 D postoperatively. There was a slight improvement of 0.1 Snellen lines at 3-months follow-up. Compared to the preoperative status, ocular aberrations (at 6 mm diameter) did not change at 3 months follow-up; whereas corneal aberrations increased (+0.22 ± 0.21 µm for coma; +0.17 ± 0.19 µm for spherical aberration; and +0.32 ± 0.26 µm for HOA-RMS). The same correction was determined using changes in ocular wavefront refraction, as well as changes in keratometric readings. CONCLUSION: Lenticule extraction after SmartSight is safe and efficacious in the first 3 months postoperatively. The post-operative outcomes indicate improvements in vision.

Predictability of the Achieved Lenticule Thickness in Keratorefractive Lenticule Extraction for Myopia Correction.

PURPOSE: To assess the predictability between the SCHWIND ATOS femtosecond laser (SCHWIND eye-tech-solutions) read-out and achieved lenticule thickness measured using MS-39 anterior segment optical coherence tomography (ASOCT; CSO) at the corneal vertex at postoperative 1 day and 1 and 3 months of follow-up. METHODS: This retrospective case series included 130 eyes of 65 consecutive patients who were treated with SmartSight (SCHWIND eye-tech-solutions) lenticule extraction. Sixty-four percent of patients were women with a mean spherical refraction of -4.98 ± 1.19 diopters (D) and mean astigmatism of 0.53 ± 0.64 D. The measurements were performed using AS-OCT with the Phoenix Software v 4.1.1.5. Lenticule thickness was obtained by the subtraction method between preoperative and postoperative total corneal thickness. RESULTS: A lower reduction in central corneal thickness (CCT) compared to the laser read-out for all three follow-up visits can be observed. Essentially, the reduction in CCT was identical at 3 months versus 1 month. The reduction in CCT was lowest at postoperative 1 day. Examining the 1- and 3-month data (essentially equivalent), one can see a best fit of y = 0.94 x -7 µm. CONCLUSIONS: The reduction in CCT was stable from 1 month of follow-up. The stable reduction in CCT was -6% (-1.5% after accounting for design decisions) and -7 µm lower than the respective laser read-out. The findings are predictable, showing a certain level of the lenticules becoming slightly thinner than their respective laser read-outs. [J Refract Surg. 2023;39(11):728-735.].

Presbyopia correction using the monocular bi-aspheric ablation profile in myopic eyes.

PURPOSE: To analyze the 6-month outcomes of the treatment combination of the monocular bi-aspheric ablation profile (PresbyMAX) and contralateral aspheric monofocal laser in situ keratomileusis (LASIK) ablation profile for correction of myopia and presbyopia. SETTING: Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea. DESIGN: Retrospective case series. METHODS: This was a retrospective case review of 92 patients (184 eyes) diagnosed with myopia who underwent uneventful simultaneous bi-aspheric ablation in the nondominant eye and aspheric monofocal regular LASIK in the dominant eye to correct myopia and presbyopia between January 2017 and August 2020. Monocular and binocular uncorrected distance visual acuity (UDVA) and near visual acuity (UNVA), and corrected distance visual acuity and near visual acuity were analyzed postoperatively. RESULTS: At 6 months postoperatively, the mean UDVAs (logMAR) in the dominant and nondominant eyes were 0.01 ± 0.02 and 0.26 ± 0.15, respectively. Furthermore, all treated dominant eyes achieved 20/20 or better monocular UDVA, and 84% achieved 20/16 or better monocular UDVA. In the nondominant treated eyes, 89% achieved 20/50 or better monocular UDVA, 78% achieved 20/40 or better, and 34% achieved 20/32 or better. The binocular cumulative UDVA at 6 months postoperatively was 20/20 or better in all patients. All patients achieved J2 or better in binocular cumulative UNVA, and 83% achieved J1. CONCLUSIONS: Presbyopia correction using the combination of PresbyMAX in the near eye and aspheric monofocal regular LASIK in the distant eye is a safe and effective treatment for presbyopia in patients with myopia.

New asymmetric centration strategy combining pupil and corneal vertex information for ablation procedures in refractive surgery: theoretical background.

PURPOSE: To describe a method for centering ablation profiles considering pupil center and corneal vertex information simultaneously. METHODS: Novel ablation profiles were developed to cover the pupil aperture while respecting the corneal vertex as the optical axis of the ablation (asymmetric offset [AO]). The approach has been extended to combine higher order aberrations (HOA) referred to the pupil center (line-of-sight) with manifest refraction values referred to the corneal vertex (visual axis). The shapes and sizes of ablation profiles planned with AO were compared with the shapes and sizes of "classic" ablation profiles (with symmetric offset and without [no] offset, respectively). RESULTS: The introduction of asymmetric offset leads to an asymmetric ablation profile that is virtually the same depth as no offset ablation profiles (symmetric offset profiles ablate deeper), with the same diameter as no offset ablation profiles (smaller than symmetric offset ablations). The ablation volume of AO profiles lies between the ablation volumes of no offset and symmetric offset ablation profiles. When combined with HOAs, AO ablation profiles affect specific HOA terms. Asymmetric offset spherical components affect HOA coma components, and AO astigmatic components affect HOA trefoil components. CONCLUSIONS: Asymmetric offset ablation profiles provide a simple method to combine pupil and corneal vertex information for ablation procedures in refractive surgery with the optical axis of the ablation lying on the visual axis and the edges of the optical zone being concentric to the pupil boundaries. Further clinical studies must be performed to support the theoretical results.

Corneal higher order aberrations after LASIK for high myopia with a fast repetition rate excimer laser, optimized ablation profile, and femtosecond laser-assisted flap.

PURPOSE: To evaluate corneal higher order aberrations (HOAs) after LASIK for the correction of high myopia using a new generation of excimer laser (500-Hz repetition rate) and optimized ablation profiles. METHODS: Retrospective consecutive study including 29 eyes from 17 patients (age range: 24 to 61 years) with high levels of myopia (spherical equivalent refraction ≥8.50 diopters). All cases underwent LASIK using the sixth-generation Amaris (SCHWIND eye-tech-solutions) excimer laser and flap creation with the IntraLase (Abbott Medical Optics) femtosecond laser. Postoperative changes in corneal HOAs and corneal asphericity were analyzed during 6-month follow-up. RESULTS: Significant improvement in uncorrected distance visual acuity and spherical equivalent was observed (P<.01). Corrected distance visual acuity did not change after surgery (P=.37). Significant increases in corneal root-mean-square (RMS) HOA, RMS spherical aberration (SA), and RMS coma were observed 6 months after surgery (P<.01). Corneal asphericity for the 4.5-mm (Q45) and 8-mm (Q8) corneal diameter also increased significantly during the postoperative period (P<.01). Significant correlations were found between postoperative RMS HOA and RMS SA and RMS coma (r(2)=0.375, P=0.000 and r(2)=0.596, P=.000, respectively). Linear regression analysis showed a significant relationship between postoperative Q45 and preoperative pachymetry and treatment optical zone (R(2)=0.24, P<.05). A correlation was also found between postoperative Q8 and preoperative sphere and treatment ablation zone (R(2)=0.459, P<.006). CONCLUSIONS: A significant induction of corneal HOAs still exists with the latest generation Schwind excimer laser. Linear regression analysis will help predict postoperative asphericity obtained when using LASIK for the correction of high myopia.

Stability of therapeutic retreatment of corneal wavefront customized ablation with the SCHWIND CAM: 4-year data.

PURPOSE: To evaluate the long-term outcomes of aspheric corneal wavefront ablation profiles for excimer laser retreatment. METHODS: Eighteen eyes that had previously undergone LASIK or photorefractive keratectomy (PRK) were retreated with LASIK using the corneal wavefront ablation profile. Custom Ablation Manager (SCHWIND eye-tech-solutions, Kleinostheim, Germany) software and the ESIRIS flying spot excimer laser system (SCHWIND) were used to perform the ablations. Refractive outcomes and wavefront data are reported up to 4 years after retreatment. Pre- and postoperative data were compared with Student t tests and (multivariate) correlation tests. P<.05 was considered statistically significant. A bilinear correlation of various postoperative wavefront aberrations versus planned correction and preoperative aberration was performed. RESULTS: Mean manifest refraction spherical equivalent (MRSE) before retreatment was -0.38±1.85 diopters (D) and -0.09±0.22 D at 6 months and -0.10±0.38 D at 4 years postoperatively. The reduction in MRSE was statistically significant at both postoperative time points (P<.005). Postoperative aberrations were statistically lower (spherical aberration P<.05; coma P<.005; root-mean-square higher order aberration P<.0001) at 4 years postoperatively. Distribution of the postoperative uncorrected distance visual acuity (P<.0001) and corrected distance visual acuity (P<.01) were statistically better than preoperative values. CONCLUSIONS: Aspheric corneal wavefront customization with the ESIRIS yields visual, optical, and refractive results comparable to those of other wavefront-guided customized techniques for the correction of myopia and myopic astigmatism. The corneal wavefront customized approach shows its strength in cases where abnormal optical systems are expected. Systematic wavefront customized corneal ablation appears safe and efficacious for retreatment cases.

In vivo measurements of thermal load during ablation in high-speed laser corneal refractive surgery.

PURPOSE: To evaluate the thermal load of ablation in high-speed laser corneal refractive surgery with the AMARIS excimer laser (SCHWIND eye-tech-solutions). METHODS: Thermal load from refractive corrections on human corneas using a 500-Hz laser system with a fluence of 500 mJ/cm(2) and aspheric ablation profiles was recorded with an infrared thermography camera. Each single in vivo measurement was analyzed and temperature values were evaluated. RESULTS: Overall, the maximum temperature change of the ocular surface induced by the refractive ablations was ≤4°C. The increase in the peak temperature of the ocular surface never exceeded 35°C in any case. This low thermal load was independent of the amount of correction the eye achieved. CONCLUSIONS: The thermal load of the ablation in high-speed laser corneal refractive surgery was minimized using a computer algorithm to control the peak temperature to avoid corneal collagen denaturation with minimal compromise on treatment duration.

Refractive Effect of Epithelial Remodelling in Myopia after Transepithelial Photorefractive Keratectomy.

(1) Introduction: We analysed epithelial changes after the treatment of moderate myopia with transepithelial photorefractive keratectomy. (2) Materials and Methods: We used optical coherence tomography data and analysed changes in the stroma and epithelium after ablation. We aimed to ascertain how much epithelium hyperplasia occurred after TransPRK; for this, we used data from 50 eyes treated with TransPRK with the AMARIS 1050 Hz, with a minimum follow-up of 4 months. (3) Results: The measured epithelial changes corresponded to a less than 0.1 ± 0.2D of spherical effect, less than 0.2 ± 0.2D of astigmatic effect, and less than 0.5 ± 0.2D of comatic effect. (4) Conclusions: The changes in epithelial thickness after aberration-neutral transepithelial photorefractive keratectomy for moderate myopia were very small, indicating a low level of epithelial hyperplasia without resembling a regression-inducing lentoid.