Higher-order aberrations after wavefront-optimized photorefractive keratectomy and laser in situ keratomileusis

Cataract surgery following refractive surgery: Principles to achieve optical success and patient satisfaction

A growing number of patients with prior refractive surgery are now presenting for cataract surgery. Surgeons face a number of unique challenges in this patient population that tends to be highly motivated to retain or regain functional uncorrected acuity postoperatively. Primary challenges include recognition of the specific type of prior surgery, use of appropriate intraocular lens (IOL) power calculation formulas, matching IOL style with spherical aberration profile, the recognition of corneal imaging patterns that are and are not compatible with toric and/or presbyopia-correcting lens implantation, and surgical technique modifications, which are particularly relevant in eyes with prior radial keratotomy or phakic IOL implantation. Despite advancements in IOL power formulae, corneal imaging, and IOL options that have improved our ability to achieve targeted postoperative refractive outcomes, accuracy and predictability remain inferior to eyes that undergo cataract surgery without a history of corneal refractive surgery. Thus, preoperative evaluation of patients who will and will not be candidates for postoperative refractive surgical enhancements is also paramount. We provide an overview of the specific challenges in this population and offer evidence-based strategies and considerations for optimizing surgical outcomes.

Corneal Higher-Order Aberrations Measurements: Precision of SD-OCT/Placido Topography and Comparison with a Scheimpflug/Placido Topography in Eyes After Small-Incision Lenticule Extraction

INTRODUCTION

The aim of this study was to evaluate the measurements of corneal higher-order aberrations (HOAs) obtained by a new anterior segment optical coherence tomography (OCT) technique combined with a Placido topographer (the MS-39 device) in eyes with prior small-incision lenticule extraction (SMILE) and compare them to the measurements obtained by a Scheimpflug camera combined with a Placido topographer (the Sirius device).

METHODS

A total of 56 eyes (56 patients) were included in this prospective study. Corneal aberrations were analyzed for the anterior, posterior, and total cornea surfaces. Within-subject standard deviation (S_w), test-retest repeatability (TRT), and intraclass correlation coefficient (ICC) were used to assess the intraobserver repeatability and interobserver reproducibility. The differences were evaluated by paired t-test. Bland-Altman plots and 95% limits of agreement (95% LoA) were used to evaluate the agreement.

RESULTS

High repeatability was observed for anterior and total corneal parameters, with S_w value < 0.07, TRT ≤ 0.16, and ICCs > 0.893, but not trefoil. For the posterior corneal parameters, ICCs varied from 0.088 to 0.966. Regarding interobserver reproducibility, all S_w values were ≤ 0.04 and TRT ≤ 0.11. ICCs ranged from 0.846 to 0.989, from 0.432 to 0.972, and from 0.798 to 0.985 for the anterior, total, and posterior corneal aberrations parameters, respectively. The mean difference in all aberrations was ≤ 0.05 μm. All parameters showed a narrow 95% LoA.

CONCLUSION

The MS-39 device achieved high precision in both anterior and total corneal measurements; the precision of posterior corneal higher-order RMS, astigmatism II, coma, and trefoil was lower. The two technologies used by the MS-39 and Sirius devices can be used interchangeably for measuring corneal HOAs after SMILE.

Ocular aberrations in eyes with Primary Congenital Glaucoma

PURPOSE

To highlight the magnitude of ocular higher order aberrations (HOA) and lower order aberrations (LOA), including component contributions from corneal and internal planes in Primary Congenital Glaucoma (PCG) patients.

METHODS

Consecutive treated PCG patients co-operative for ocular examination and aberrometry, were enrolled over two years for this cross-sectional, comparative, single centre, unmasked study. Best corrected visual acuity, refraction, IOP, wavefront aberrometry and topography (iTrace) were performed and results were compared with unaffected fellow eyes of unilateral glaucoma patients as well as age and sex matched controls with no ocular anomalies other than treatable refractive error.

RESULTS

Both eyes of 32 consecutive PCG patients (17 unilateral, 15 bilateral) and 39 controls were enrolled. The median LogMAR corrected distance visual acuity of PCG eyes was 0.68 (IQR: 0.2 - 1.8). Total ocular (Root mean square (RMS) 1.7µm vs 0.3µm, p = 0.014), corneal (RMS 1.1µm vs 0.3µm, p = 0.004) and internal (RMS 1.1µm vs 0.2µm, p = 0.013) aberrations, as well as HOAs and LOAs at each plane were significantly higher in PCG eyes than in controls. Component HOAs from corneal and internal planes were positively correlated with each other (p < 0.001; rs: 0.7). Total aberrations were greater in the affected eyes of PCG compared to the rest. The predominant subtype of HOAs in PCG were coma and trefoil. PCG with corneal opacity/Haab's striae had significantly higher astigmatism than the affected eyes with clear corneae at corneal plane (p = 0.02). The aberrations were not statistically associated with the corneal diameter or refractive error in PCG eyes.

CONCLUSIONS

Significantly greater aberrations (Total, HOAs and LOAs, at corneal as well as internal plane) were seen among eyes affected with PCG. Though the exact impact of these aberrations on the final visual outcome is difficult to determine, these could play a pertinent role in compromising visual function, thus impacting the management of visual rehabilitation in these patients.

Two-Year Changes in Corneal Spherical Aberration After Laser-Assisted In Situ Keratomileusis and Photorefractive Keratectomy in Regular and Wavefront-Guided Ablations

INTRODUCTION

The aim of this study was to analyze the changes in corneal spherical aberration following regular ablation (RA) and wavefront-guided (WFG) ablations in photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK).

METHODS

A retrospective analysis was performed on the eyes that underwent femtosecond LASIK or PRK between January 2016 and December 2018. Changes in the corneal spherical aberration were measured preoperatively and postoperatively with a high-resolution Scheimpflug camera system, and they were correlated with the attempted correction and all other tomography parameters.

RESULTS

Of the 3826 eyes that were reviewed, 484 eyes met the inclusion criteria and were enrolled in the study. Seventy-four eyes underwent PRK and 410 eyes underwent LASIK. The LASIK and PRK subgroups were similar in terms of the general demographics, preoperative higher-order aberrations, and manifest spherical equivalent. The changes in spherical aberration were significantly correlated with the attempted correction in both LASIK (y =  -0.35x and R² = 0.42 for myopic WFG; y =  -0.18x and R² = 0.19 for myopic RA; y =  -0.44x and R² = 0.49 for hyperopic WFG; y =  -0.53x and R² = 0.69 for hyperopic RA) and PRK (y = -0.20x and R² = 0.25 for myopic WFG; y = -0.37x and R² = 0.44 for myopic RA). No other preoperative parameters except corneal asphericity, axial length, and anterior chamber depth were significantly correlated with the changes in the spherical aberration.

CONCLUSIONS

LASIK correction had a higher induction of spherical aberration compared with that of PRK, and the beneficial effect of the WFG treatment on spherical aberration was mainly visible in the PRK-treated eyes.

One-Year Outcomes From a Prospective, Randomized, Eye-to-Eye Comparison of Wavefront-Guided and Wavefront-Optimized PRK in Myopia

PURPOSE

To compare wavefront-guided (WFG) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) in patients with myopia using objective and self-reported quality of vision outcomes.

METHODS

A total of 40 eyes from 20 participants were prospectively randomized to receive WFG or WFO PRK with the WaveLight Allegretto Eye-Q 400-Hz excimer laser (Alcon Laboratories, Inc., Fort Worth, TX). The primary outcome measured was uncorrected distance visual acuity (UDVA) at 12 months postoperatively. Secondary outcome measures included corrected distance visual acuity (CDVA), less than 5% and less than 25% contrast visual acuity, changes in higher order aberrations (HOAs), and self-reported quality of vision. Patients completed a validated, Rasch-tested, linear-scaled 30-item questionnaire assessing the quality of vision and visual symptoms preoperatively and at each visit.

RESULTS

There was no statistically significant difference (P > .05) between the WFG and WFO groups in the frequency of attaining a refractive error within ±0.25 diopters of emmetropia, achieving postoperative UDVA of 20/16 or better or 20/20 or better, losing one or two or more lines or maintaining their preoperative CDVA, or differences in UDVA, CDVA, low contrast acuity, or HOAs. None of the measured quality of vision parameters exhibited statistically significant differences between the groups preoperatively or at 12 months postoperatively (all P > .05). The WFG and WFO groups each showed significant improvement in multiple subjective measures compared to pretreatment values in the same eye. A total of 12.5% of patients preferred their WFG PRK eye, 31.25% preferred their WFO PRK eye, and 56.25% had no preference at 12 months postoperatively.

CONCLUSIONS

WFG and WFO PRK using the Alcon Wave-Light Allegretto Eye-Q 400-Hz excimer laser platform provide similar results and self-reported visual symptoms in myopic eyes at 12 months postoperatively. [J Refract Surg. 2020;36(3):160-168.].

Corneal higher-order aberrations measurements: Comparison between Scheimpflug and dual Scheimpflug-Placido technology in keratoconic eyes

PURPOSE

To compare the difference and agreement of corneal higher-order aberrations (HOAs) in keratoconic eyes using Scheimpflug and dual Scheimpflug-Placido imaging systems.

SETTING

Emory University, Atlanta, Georgia, and the University of Southern California, Los Angeles, California, USA.

DESIGN

Retrospective between-devices reliability and agreement study.

METHODS

Patients diagnosed with keratoconus were evaluated sequentially by Scheimpflug and dual Scheimpflug-Placido devices. Differences, correlations, and agreement between values for total root mean square (RMS), trefoil, coma, and spherical aberration were analyzed, and Bland-Altman plots were generated.

RESULTS

Fifty eyes from 50 patients (31 men, 19 women) were evaluated. Trefoil at 30 degrees, spherical aberration, and total RMS were significantly different between groups (P < .05), whereas trefoil at 0 degrees and total coma values were not statistically different. There was a weak positive correlation between devices for trefoil at 0 degrees (r = 0.228), and a moderate positive correlation for trefoil at 30 degrees (r = 0.473), horizontal coma (r = 0.430), and for total corneal RMS (r = 0.637). Vertical coma (r = 0.816) and spherical aberration (r = 0.874) showed a strong positive correlation. The 95% limits of agreement (LoA) for absolute values were 1.963 μm for trefoil at 30 degrees, 2.449 μm for trefoil at 0 degrees, 3.530 μm for horizontal coma, 2.145 μm for vertical coma, 1.242 μm for spherical aberration, and 10.527 μm for RMS.

CONCLUSION

Significant differences were found between measurements of corneal HOAs generated by Scheimpflug and dual Scheimpflug-Placido devices in patients with keratoconus, with generally limited correlations and wide LoA. HOAs measurements from these devices should not be considered equivalent.

Higher-order aberration measurements: Comparison between Scheimpflug and dual Scheimpflug-Placido technology in normal eyes

PURPOSE

To compare higher order aberrations (HOAs) in normal eyes between a Scheimpflug imaging system (Pentacam HR) and dual Scheimpflug-Placido imaging system (Galilei G4).

SETTING

Emory University, Atlanta, Georgia, and the University of Southern California, Los Angeles, USA.

DESIGN

Retrospective case series.

METHODS

Eyes screened for refractive surgery were evaluated sequentially using a Scheimpflug device and a dual Scheimpflug-Placido device. Differences, correlations, and agreement between values for total root mean square (RMS), trefoil, coma, and spherical aberration were analyzed, and Bland-Altman plots were generated.

RESULTS

One hundred five eyes of 105 patients (44 men, 61 women) were evaluated. Total RMS, coma, and trefoil were significantly different between groups (all P < .001), while spherical aberration values were not. There was moderate correlation between devices for trefoil (r = 0.475 to 0.652), coma (r = 0.574 to 0.651), and spherical aberration (r = 0.483) and a strong correlation for total cornea RMS (r = 0.817). There was no directional bias between groups. The 95% limits of agreement for absolute values was 0.039 μm for trefoil at 30 degrees, 0.405 μm for trefoil at 0 degree, 0.553 μm for horizontal coma, 0.545 μm for vertical coma, 0.318 μm for spherical aberration, and 0.617 μm for RMS.

CONCLUSIONS

A Scheimpflug imaging device and dual Scheimpflug-Placido imaging device generated statistically different values for total cornea HOAs; however, the correlation between devices was moderate to strong and there was reasonable agreement in all measures for normal eyes. Based on these findings, the devices appear functionally equivalent for clinical use, although caution is warranted for outcomes-based research protocols that report HOAs.

Excimer Lasers in Refractive Surgery

Introduction

In the field of ophthalmology, laser technology is used in many basic and clinical disciplines and specialities. It has played an important role in promoting the development of ophthalmology.

Aim

This article is designed to review the evolution of laser technology in refractive surgeries in ophthalmology, mainly focusing on the characteristics of the excimer laser applied in corneal refractive surgery.

Methods

This article was performed based on a literature review and Internet search through scientific databases such as PubMed, Scopus, Web of Science and Google Scholar.

Result

The literature on excimer laser technology addresses the technical and physical aspects of excimer lasers including types, characteristics and commercially available lasers on the market.

Conclusion

The conclusion on this forum aims to help understand the benefits of excimer laser use in ophthalmology, with focus on correction of refractive errors.

Intraocular lens calculations after laser vision correction

PURPOSE OF REVIEW

This article describes different strategies for corneal measurements and/or intraocular lens (IOL) calculations and proposes a systematic approach for IOL selection in patients who have undergone laser corneal refractive surgery.

RECENT FINDINGS

Corneal measurements and IOL calculations cannot be obtained accurately with the standard measuring technologies and formulas in patients with history of laser corneal refractive surgery; therefore a variety of methods and formulas, some of which required prerefractive surgery data, have been proposed to improve the accuracy of measurements and calculations. Formulas that do not rely on prerefractive data seem to be as accurate as those that do; therefore the lack of prerefractive data no longer presents an obstacle for accurate IOL selection in these patients.

SUMMARY

Postrefractive patients undergoing cataract extraction and IOL implantation should have corneal measurements and IOL calculations that take into account and compensate for the limitations in accurate measurements and calculations. IOL selection should also aim to compensate for induced spherical aberration according to the ablation pattern.

Comparison of Higher Order Aberrations after Wavefront-guided LASIK and PRK: One Year Follow-Up Results

PURPOSE

To evaluate the changes and predictability of higher order aberrations (HOAs) after personalized laser in situ keratomileusis (LASIK) and personalized photorefractive keratectomy (PRK) for simple myopia and compound myopic astigmatism.

METHODS

In this prospective cross-sectional study, 100 eyes were included. A total of 50 eyes underwent personalized LASIK and 50 eyes underwent personalized PRK. Preoperative and postoperative wavefront data were compared between the two groups. The influential factors and predictability of HOAs were also assessed.

RESULT

Total HOA increased in the amount of 0.01 ± 0.14 μm for the 5 mm pupil (P = 0.55) and 0.08 ± 0.22 μm for the 6 mm pupil (P = 0.02) after PRK; however after LASIK the corresponding values for the 5 and 6 mm pupil sizes were 0.05 ± 0.12 and 0.15 ± 0.18 μm, respectively (P < 0. 001). Mean changes were not significantly different between the PRK and LASIK groups for both 5 and 6 mm pupil sizes (P = 0.21 and P = 0.13, respectively). Spherical aberration increased following LASIK more than following PRK (P < 0.001). Changes in the root mean square (RMS) of total HOA had a statistically significant negative correlation (P < 0.001) with its preoperative value. HOA and spherical aberration reduced in majority of eyes when the preoperative spherical equivalent refraction was low.

CONCLUSION

For the 6mm pupil size, the total HOA increased following both personalized PRK and LASIK with no significant difference between the two groups. Change of the total HOA RMS was influenced by the preoperative values. The known influencing factors could predict nearly 50% of the changes in total HOA.

Comparison of Measurements and Clinical Outcomes After Wavefront-Guided LASEK Between iDesign and WaveScan

PURPOSE

To compare the measurements of refractive errors and ocular aberrations obtained using iDesign and WaveScan (Abbott Medical Optics, Inc., Santa Ana, CA), and to compare surgical outcomes of wavefront-guided LASEK using ablation profiles based on both aberrometers.

METHODS

Ninety myopic eyes of 45 normal patients were evaluated using both the iDesign and WaveScan to measure spherical and cylindrical errors, spherical equivalents, and Zernike coefficients of ocular aberrations. Wavefront-guided LASEK was performed in a different group of 59 eyes of 30 patients divided into two groups, the iDesign and Wavescan groups. The clinical outcomes between the two groups including uncorrected visual acuity, refractive errors, contrast sensitivity, and ocular aberration were compared at 1, 3, and 6 months postoperatively.

RESULTS

The iDesign produced significantly higher myopic values for refractive errors than the WaveScan, as well as significantly lower levels of total higher order, third, fourth, and fifth order root mean square values and Zernike coefficients of vertical coma and spherical aberration. At postoperative 1, 3, and 6 months, there were no statistically significant differences between the two groups in terms of uncorrected visual acuity and remaining refractive errors. The percentages of patients with spherical equivalents within ±1.00 and ±0.50 diopters of emmetropia were 100% (29 eyes) and 75.9% (22 eyes), respectively, in the iDesign group and 96.7% (29 eyes) and 70.0% (21 eyes), respectively, in the WaveScan group. Mesopic contrast sensitivity values were significantly higher, and the change in root mean square values for spherical aberration was significantly lower in the iDesign group.

CONCLUSIONS

There were significant differences between the iDesign and the WaveScan in the measurements of refraction and ocular aberrations. Wavefront-guided LASEK based on an ablation profile from the iDesign demonstrated comparable refractive predictability with the WaveScan group, resulting in minimal physician adjustment and superior postoperative visual quality.

Comparison of visual outcomes after variable spot scanning ablation versus wavefront-optimized myopic LASIK

PURPOSE

To compare the refractive and visual outcomes of variable spot scanning ablation versus the wavefront-optimized ablation for myopia and myopic astigmatism.

METHODS

Fifty patients with myopia who underwent LASIK (100 eyes) were divided into two equal groups. Myopic correction performed using the variable spot scanning (VSS) ablation with the VISX STAR S4/IR platform (Abbott Medical Optics, Inc., Santa Ana, CA) (VSS group) and wavefront-optimized (WFO) ablation profile with the WaveLight Allegretto Wave Eye-Q platform (Alcon Laboratories, Inc., Fort Worth, TX) (WFO group). Manifest refraction, uncorrected distance visual acuity, and corrected distance visual acuity were obtained preoperatively and 1 day and 1 and 3 months postoperatively. Wavefront measurement and contrast sensitivity testing were done preoperatively and 3 months postoperatively.

RESULTS

Postoperative mean refractive spherical equivalent was -0.14 ± 0.2 diopters for the VSS group and -0.15 ± 0.28 diopters for the WFO group. Forty-eight eyes of the VSS group and 47 eyes of the WFO group were within ±0.5 diopters. Postoperative mean corrected distance visual acuity was 1.05 ± 0.13 for the VSS group and 1.06 ± 0.12 for the WFO group. The postoperative uncorrected distance visual acuity was 1.01 ± 0.16 for the VSS group and 1.01 ± 0.11 for the WFO group. The safety index was 1.12 for the VSS group and 1.06 for the WFO group, whereas the efficacy index was 1.07 for the VSS group and 1.01 for the WFO group. The mean induced positive spherical aberration was 0.041 ± 0.046 µm for the VSS group and 0.195 ± 0.171 µm for the WFO group (P < .001). Mesopic contrast sensitivity testing showed no statistically significant differences between groups at all tested spatial frequencies.

CONCLUSIONS

Both VSS and WFO treatments showed similar refractive and visual outcomes. Both induced significant positive spherical aberration, significantly more with WFO.

Single-step transepithelial ASLA (SCHWIND) with mitomycin-C for the correction of high myopia: long term follow-up

PURPOSE

We wanted to compare the outcomes of single-step modified transepithelial photorefractive keratectomy (tPRK) termed a SCHWIND all surface laser ablation (ASLA) versus conventional alcohol-assisted photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK) for the correction of higher myopia of 6.00 diopters (D) or more, in an area with high risk of haze due to high intensity of sunlight.

METHODS

We used a prospective interventional cohort with matched retrospective control groups. Patients with >6 D myopia and <3.5 D of astigmatism were included. All treatments were performed with the SCHWIND Amaris system using aspheric ablation profiles. Mitomycin C was used in all PRK and ASLA cases. Outcomes were postoperative refraction, visual acuity, stability, and complications. The follow-up period was up to 12 months.

RESULTS

In total, 101 eyes were included after exclusions. Mean preoperative spherical equivalent refraction was -7.9 D, -8.2 D, and -7.4 D in the ASLA (n=41), PRK (n=29), and LASIK (n=31) groups. Mean postoperative spherical equivalent at 12 months postoperatively was -0.1 (standard deviation [SD]: 0.34), -0.2 (SD: 0.59), and -0.08 (SD: 0.36) in the ASLA, PRK, and LASIK groups, with 91.4%, 85.7%, and 83.9% within 0.5 D of target, respectively. Refractive outcomes and regression at 12 months did not vary among groups (P>0.05). Mean logMAR (logarithm of the minimum angle of resolution) uncorrected distance visual acuity at 12 months was 0.00 (SD: 0.05), 0.06 (SD: 0.1), and 0.05 (SD: 0.09) in the ASLA, PRK, and LASIK groups, with significantly better vision in the tPRK group versus LASIK (P=0.01) and PRK (P=0.01) groups.

CONCLUSION

ASLA (SCHWIND) tPRK with mitomycin C for high myopia demonstrates comparable refractive outcomes to LASIK and PRK, with relatively favorable visual acuity outcomes. There was no increased incidence of haze in the ASLA group.

Therapeutic flap amputation for atypical LASIK flap and interface abnormalities

PURPOSE

To describe LASIK flap amputation as a therapeutic option for patients with atypical refractory flap complications.

METHODS

Case series and literature review.

RESULTS

Seven eyes of 6 patients underwent flap amputation for various atypical indications, including non-infectious flap/interface opacity (3 patients), irregular astigmatism on the flap surface (3 patients), and chronic pain (concurrent in 2 patients with irregular astigmatism). In each case, conservative measures were ineffective. All patients had symptomatic improvement and improved corrected visual function after amputation; however, uncorrected distance visual acuity worsened in 2 patients, manifest refraction worsened in 3 patients, and irregular astigmatism increased in 2 patients.

CONCLUSIONS

Flap amputation is a reasonable alternative to improve corrected acuity in select cases with significant flap opacities or irregular astigmatism unresponsive to conservative measures, but uncorrected acuity and irregular astigmatism may worsen and should be discussed during the informed consent process.

Describing the corneal shape after wavefront-optimized photorefractive keratectomy

PURPOSE

To develop a procedure for describing wavefront-optimized photorefractive keratectomy (PRK) corneas and to characterize PRK-induced changes in shape.

METHODS

We analyzed preoperative and postoperative corneal elevation data of 41 eyes of 41 patients (mean [±SD] age, 38 [±11] years) who underwent a myopia-correcting (preoperative spherical equivalent refraction -3.9 [±1.5] diopters) wavefront-optimized PRK, assessed with Scheimpflug imaging. Zernike polynomials were fitted to the elevation data. The diameter of the greatest corneal zone that could be analyzed and the number of Zernike orders needed to make a reliable fit were determined, based on the fitting error. The PRK-induced changes in corneal shape were studied.

RESULTS

All subjects could be included for analysis of zones up to 6 mm in diameter. This was 90, 83, and 44% for 7, 8, and 9 mm, respectively. The number of Zernike orders (terms) needed for an accurate fit ranged from four (15) for a 4-mm analyzed zone diameter to eight (45) for 8 mm. For the anterior surface, the spherical aberration term decreased significantly (p < 0.01) after PRK for the 4-mm analyzed zone diameter (-0.09 μm), remained unchanged for 5 mm (+0.01 μm; p = 0.56), and increased significantly for 6 mm (+0.40 μm) and above (p < 0.01). There was no significant change in any other higher-order Zernike term, but the square root of the sum of the squares of all higher-order terms increased significantly for all analyzed zone diameters. Photorefractive keratectomy did not influence the posterior corneal shape.

CONCLUSIONS

The cornea after wavefront-optimized PRK can be described as accurately as a healthy cornea and with a similar number of Zernike polynomials. The anterior corneal shape changes significantly after treatment, whereas the posterior corneal shape remains unchanged. The observed effect of wavefront-optimized ablation on the spherical aberration term depends on the diameter of the analyzed zone.

Effects of mitomycin-C on tear film, corneal biomechanics, and surface irregularity in mild to moderate myopic surface ablation: preliminary results

PURPOSE

To assess the effect of mitomycin-C (MMC) on the tear film, corneal biomechanics, and surface irregularity in surface ablation (photorefractive keratectomy [PRK]) for low to moderate myopia.

SETTING

Refractive Surgery Unit, Farabi Eye Hospital, Tehran, Iran.

DESIGN

Double-masked randomized clinical trial.

METHODS

In patients with spherical equivalent myopia of -0.75 to -3.87 diopters (D) and astigmatism up to -1.75 D, the first eye was randomly assigned to the application of MMC 0.02% or a balanced salt solution for 15 seconds. The fellow eye received the alternate in a masked fashion after excimer photoablation.

RESULTS

The study enrolled 60 patients. In fellow eyes, the changes in the tear-film index were comparable 1 month and 6 months postoperatively. There was no significant difference in changes in total higher-order aberrations, spherical aberration, coma, or Q values (Pentacam HR) between fellow eyes at 1 month and 6 months. There was a trend toward a higher asymmetry index at 1 month; however, a statistically significant drop was observed at 6 months in the MMC group (P<.01). It was hypothesized that stromal remodeling was delayed, but better, in MMC-treated eyes. No haze was recorded at 6 months in either group.

CONCLUSION

Use of MMC in PRK did not appear to contribute significantly to surface irregularity, transient tear-film dysfunction, or biomechanical weakening of the cornea compared with PRK without MMC.

FINANCIAL DISCLOSURE

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

One-year outcomes from a prospective, randomized, eye-to-eye comparison of wavefront-guided and wavefront-optimized LASIK in myopes

OBJECTIVE

To compare wavefront (WF)-guided and WF-optimized LASIK in myopes.

DESIGN

Prospective, randomized, eye-to-eye study.

PARTICIPANTS

A total of 72 eyes of 36 participants with myopia with or without astigmatism.

METHODS

Participants were randomized to receive WF-guided or WF-optimized LASIK with the WaveLight Allegretto Eye-Q 400-Hz excimer laser platform (Alcon, Inc., Hüenberg, Switzerland). LASIK flaps were created using the 150-kHz IntraLase iFS (Abbott Medical Optics, Santa Ana, CA). Evaluations included measurement of uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), <5% and <25% contrast sensitivity, and WF aberrometry. Patients also completed a validated questionnaire detailing symptoms on a quantitative scale.

MAIN OUTCOME MEASURES

Safety, efficacy, predictability, refractive error, UDVA, CDVA, contrast sensitivity, and higher-order aberrations (HOAs).

RESULTS

The frequency with which the WF-guided and WF-optimized groups achieved postoperative UDVA of ≥ 20/16 or ≥ 20/20 and the frequency with which the groups lost 1 or 2 or more lines or maintained their preoperative CDVA were not statistically different from each other (all P > 0.05). The frequency with which the WF-guided group attained a refractive error within ± 0.25 diopters of emmetropia was higher than in the WF-optimized group (67.6%, 95% confidence interval [CI], 50.4-84.8 vs. 41.2%, 95% CI, 23.2-59.2; P = 0.03). The WF-guided group's mean UDVA was better than the WF-optimized group's UDVA by approximately 1 Early Treatment Diabetic Retinopathy Study line (-0.17 ± 0.11 logarithm of the minimum angle of resolution [logMAR], slightly <20/12 Snellen vs. -0.13 ± 0.12, slightly >20/16; P = 0.05). There were no statistically significant differences in contrast sensitivity, astigmatism, coma, or higher-order root mean square error between the groups (all P > 0.05), but the WF-guided group had less trefoil compared with the WF-optimized group (0.14 ± 0.07 vs. 0.20 ± 0.09; P < 0.01). There were no statistically significant differences in subjective parameters between the groups (all P > 0.05).

CONCLUSIONS

Wavefront-guided and WF-optimized LASIK using the Alcon WaveLight Allegretto Eye-Q 400-Hz excimer laser platform provide similar results in myopic patients; however, the WF-guided approach may yield small gains in visual acuity, predictability, and HOAs.

Flap-off epi-LASIK versus automated epithelial brush in PRK: a prospective comparison study of pain and reepithelialization times

PURPOSE

To compare the effect of flap-off epi-LASIK versus automated brush epithelial removal on pain and wound healing in low myopic photorefractive keratectomy (PRK).

METHODS

In this prospective intraindividual study 60 patients received surface ablation in each eye. Epithelial removal was performed by an automated brush technique in one eye (brush group) and epi-LASIK with flap removal (flap-off group) in the fellow eye. The epithelial defect size was measured daily after surgery until both eyes were reepithelialized. Postoperative pain on a scale from 0 to 6 and topical and oral analgesic medication use was recorded until the bandage contact lens was removed.

RESULTS

The flap-off group had significantly less postoperative pain on days 1 (P=.0003), 2 (P=.0001), 3 (P<.0001), and 4 (P<.0001) compared to the brush group. However, the average difference in pain scores between groups was only 0.33 points out of 6. No difference was noted in the normalized overall percentage rate of healing over the first 4 days in the flap-off group (5.41±1.39%/hour) compared to the brush group (5.42±1.94%/hour) (P=.97).

CONCLUSIONS

The flap-off group showed a statistically but not clinically significant advantage over the brush group in pain scores. However, no difference was noted in the percentage rate of epithelial healing time between the two groups.

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.

Optical quality after myopic photorefractive keratectomy and laser in situ keratomileusis: comparison using a double-pass system

PURPOSE

To use a double-pass system to compare the optical quality after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) for mild to moderate myopia.

SETTING

Universitat Politècnica de Catalunya, Terrassa, Barcelona Institute of Ocular Microsurgery, Barcelona, Spain.

DESIGN

Comparative case series.

METHODS

Optical quality was assessed with a clinical double-pass system preoperatively and 3 months after PRK or LASIK. The modulation transfer function (MTF), retinal image quality parameters (MTF cutoff frequency, Strehl ratio), and intraocular scattering (objective scatter index [OSI]) were calculated.

RESULTS

This study evaluated 34 eyes that had PRK and 55 eyes that had LASIK. Both PRK and LASIK had a statistically significant impact on retinal image quality, although no significant differences between the techniques were observed. The MTF at 30 cycles per degree decreased by a factor of 1.50 in the PRK group and by a factor of 1.32 in the LASIK group. The MTF cutoff frequency decreased by a factor of 1.04 in the PRK group and by a factor of 1.06 in the LASIK group. The Strehl ratio decreased by a factor of 1.10 and 1.07, respectively. Photorefractive keratectomy and LASIK increased the objective scatter index by factors of 1.48 and 1.57, respectively. Significant correlations between the preoperative refraction and the OSI were found.

CONCLUSIONS

Retinal image quality was similarly reduced with PRK and LASIK, with no significant differences between the 2 methods. Some PRK patients had a residual refractive error that might have been related to corneal-wound healing still present 3 months postoperatively.

Near visual acuity following hyperopic photorefractive keratectomy in a presbyopic age group

Purpose. To assess near visual acuity in a presbyopic age group following hyperopic photorefractive keratectomy (PRK). Setting. Private practice in Siena, Italy. Methods. In this retrospective single-surgeon comparative study, PRK with mitomycin C was performed to correct hyperopia using Bausch & Lomb 217z laser for 120 eyes of 60 patients in the presbyopic age group (mean spherical equivalent SE +2.38 D ± 0.71 D and mean age 52 ± 5.09). 120 eyes of 60 age-matched controls (mean age 54 ± 5.09) had their unaided near vision measured. Results. At 12 months mean SE was −0.10 D ± 0.27 D in the PRK group. Mean best corrected visual acuity (BSCVA) was 0.005 ± 0.022  log MAR; 2 eyes lost ≥0.1 log MAR. Mean uncorrected visual acuity was 0.04 ± 0.077  log MAR. Mean distance corrected near visual acuity (DCNVA) in the PRK group was J3.73 ± 1.06. This was statistically better (P < 0.05) than the mean unaided near visual acuity in the control group J4.07 ± 1.08. Conclusion. PRK was found to be safe, predictable, and an effective way of correcting hyperopia in this age group. It was also found to give better than expected near vision.

Prospective, randomized, double-blind, contralateral eye comparison of myopic LASIK with optimized aspheric or prolate ablations

PURPOSE

To compare the postoperative outcomes of aspheric or prolate LASIK for myopia and myopic astigmatism.

METHODS

In this double-blind, bilateral, randomized trial, 40 patients (80 eyes) with -0.75 to -7.00 diopters (D) of manifest refraction spherical equivalent (MRSE) underwent optimized aspheric treatment zone ablation (OATz group) in 1 eye and optimized prolate ablation (OPA group) in the fellow eye. Six-month postoperative outcomes were compared for MRSE and visual acuity, contrast sensitivity, patient satisfaction, ocular higher order aberrations (HOAs), and spherical aberration. The Wilcoxon signed rank test, Mann-Whitney U test, and paired t test were used for testing differences between groups. P<.05 was statistically significant. Main outcome measures included HOAs, spherical aberration, visual and refractive outcomes, and contrast sensitivity.

RESULTS

Postoperatively, 36 patients (72 eyes) were evaluated. The MRSE was -0.07±0.23 D for the OPA group and +0.02±0.24 D for the OATz group (P>.05). Two (5%) eyes in the OPA group and 1 (3%) eye in the OATz group (P=.114) lost 1 line of corrected distance visual acuity. Postoperative visual acuity was not statistically different between groups (P>.05). Statistically lower change was noted in spherical aberration (0.011 μm) in the OPA group versus the OATz group (0.099 μm) (P<.001). Statistically higher induction of coma was noted in the OPA group (P=.035). No statistically significant differences were noted in photopic, mesopic, or glare contrast sensitivity and patient satisfaction between groups (P>.05, for all comparisons).

CONCLUSIONS

The refractive and visual outcomes of OPA and OATz were equivalent. However, the postoperative optical quality of OPA-treated eyes was better.

A prospective, randomized, fellow eye comparison of WaveLight® Allegretto Wave ® Eye-Q versus VISX CustomVue™ STAR S4 IR™ in laser in situ keratomileusis (LASIK): analysis of visual outcomes and higher order aberrations

Purpose

To compare outcomes in visual acuity, refractive error, higher-order aberrations (HOAs), contrast sensitivity, and dry eye in patients undergoing laser in situ keratomileusis (LASIK) using wavefront (WF) guided VISX CustomVue and WF optimized WaveLight Allegretto platforms.

Methods

In this randomized, prospective, single-masked, fellow eye study, LASIK was performed on 44 eyes (22 patients), with one eye randomized to WaveLight Allegretto, and the fellow eye receiving VISX CustomVue. Postoperative outcome measures at 3 months included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive error, root-mean-square (RMS) value of total and grouped HOAs, contrast sensitivity, and Schirmers testing.

Results

Mean values for UDVA (logMAR) were −0.067 ± 0.087 and −0.073 ± 0.092 in the WF optimized and WF guided groups, respectively (P = 0.909). UDVA of 20/20 or better was achieved in 91% of eyes undergoing LASIK with both lasers while UDVA of 20/15 or better was achieved in 64% of eyes using the Allegretto platform, and 59% of eyes using VISX CustomVue (P = 1.000). In the WF optimized group, total HOA increased 4% (P = 0.012), coma increased 11% (P = 0.065), and spherical aberration increased 19% (P = 0.214), while trefoil decreased 5% (P = 0.490). In the WF guided group, total HOA RMS decreased 9% (P = 0.126), coma decreased 18% (P = 0.144), spherical aberration decreased 27% (P = 0.713) and trefoil decreased 19% (P = 0.660). One patient lost one line of CDVA secondary to residual irregular astigmatism.

Conclusion

Both the WaveLight Allegretto and the VISX CustomVue platforms had equal visual and safety outcomes. Most wavefront optimized HOA values trended upward, with a statistically significant increase in total HOA RMS. Eyes treated with the WF guided platform showed a decreasing trend in HOA values.

Prospective, randomized, fellow eye comparison of WaveLight Allegretto Wave Eye-Q versus VISX CustomVueTM STAR S4 IRTM in photorefractive keratectomy: analysis of visual outcomes and higher-order aberrations

Background

The purpose of this study was to compare differences in visual outcomes, higher-order aberrations, contrast sensitivity, and dry eye in patients undergoing photorefractive keratectomy using wavefront-guided VISX CustomVue™ and wavefront-optimized WaveLight^® Allegretto platforms.

Methods

In this randomized, prospective, single-masked, fellow-eye study, photorefractive keratectomy was performed on 46 eyes from 23 patients, with one eye randomized to WaveLight Allegretto, and the fellow eye receiving VISX CustomVue. Three-month postoperative outcome measures included uncorrected distance visual acuity, corrected distance visual acuity, refractive error, root mean square of total and grouped higher-order aberrations, contrast sensitivity, and Schirmer’s testing.

Results

Mean values for uncorrected distance visual acuity (logMAR) were −0.03 ± 0.07 and −0.06 ± 0.09 in the wavefront-optimized and wavefront-guided groups, respectively (P = 0.121). Uncorrected distance visual acuity of 20/20 or better was achieved in 91% of eyes receiving wavefront-guided photorefractive keratectomy, and 87% of eyes receiving wavefront-optimized photorefractive keratectomy, whereas uncorrected distance visual acuity of 20/15 was achieved in 35% of the wavefront-optimized group and 64% of the wavefront-guided group (P ≥ 0.296). While root mean square of total higher-order aberration, coma, and trefoil tended to increase in the wavefront-optimized group (P = 0.091, P = 0.115, P = 0.459, respectively), only spherical aberration increased significantly (P = 0.014). Similar increases were found in wavefront- guided root mean square of total higher-order aberration (P = 0.113), coma (P = 0.403), trefoil (P = 0.603), and spherical aberration (P = 0.014). There was no significant difference in spherical aberration change when comparing the two platforms. The wavefront-guided group showed an increase in contrast sensitivity at 12 cycles per degree (P = 0.013).

Conclusion

Both VISX CustomVue and WaveLight Allegretto platforms performed equally in terms of visual acuity, safety, and predictability in photorefractive keratectomy. The wavefront-guided group showed slightly improved contrast sensitivity. Both lasers induced a comparable degree of statistically significant spherical aberration, and tended to increase other higher-order aberration measures as well.

Long-term corneal wavefront aberration variations after photorefractive keratectomy for myopia and myopic astigmatism

PURPOSE

To analyze the higher-order corneal wavefront aberration during an 8-year follow-up after photorefractive keratectomy (PRK).

SETTING

IRCCS Fondazione G.B. Bietti, Rome, Italy.

DESIGN

Case series.

METHODS

Patients having PRK using the Technolas 217C excimer laser platform were divided into 3 groups according to the preoperative refraction as follows: low myopia, high myopia, and astigmatism. The preoperative and 1-, 4-, 6-, and 8-year postoperative root mean square (RMS) values of coma, spherical aberration, and total higher-order aberrations (HOAs) were calculated with 3.5 mm and 6.0 mm simulated pupils. The mean preoperative and postoperative higher-order corneal wavefront aberration maps, point-spread functions, and radial modulation transfer functions (MTFs) were represented to describe the impact of PRK on the optical quality of the anterior cornea.

RESULTS

The study enrolled 33 patients (66 eyes). Corneal spherical aberration was statistically significantly higher after PRK for simple myopia with 3.5 mm and 6.0 mm pupils (P<.05). The postoperative increase in coma was statistically significant in the high-myopia group with both pupil sizes (P<.05). Total RMS HOAs increased postoperatively with a 6.0 mm pupil in all groups (P<.05). The mean radial MTF was almost stable in all groups between preoperatively and postoperatively.

CONCLUSIONS

Higher-order corneal wavefront aberrations stabilized 1 year after PRK to treat myopia or myopic astigmatism. The effect of induced corneal HOAs tended to increase after correction of high myopia with large pupils, although without degrading the image optical quality of the cornea over the long term.

Visual acuity and higher-order aberrations with wavefront-guided and wavefront-optimized laser in situ keratomileusis

PURPOSE

To compare visual acuity and higher-order aberrations (HOAs) after wavefront-guided and wavefront-optimized laser in situ keratomileusis (LASIK).

METHODS

This retrospective study comprised refraction-matched myopic eyes that had wavefront-guided (Visx Star S4 laser) or wavefront-optimized (WaveLight Allegretto Wave laser) LASIK targeted for emmetropia. Preoperative and postoperative manifest refraction spherical equivalent (MRSE), uncorrected (UDVA) and corrected (CDVA) distance visual acuities, and preoperative and postoperative HOAs were compared.

RESULTS

Preoperatively, there were no significant differences between the wavefront-guided and wavefront-optimized groups in age, sex, corneal thickness, MRSE, or HOAs (all P>.05). The mean MRSE was -2.88 diopters (D) +/- 2.6 (SD) and -2.96 +/- 2.6 D, respectively, preoperatively and -0.01 +/- 0.25 D and -0.02 +/- 0.33 D, respectively, postoperatively; 96% of all eyes were within +/-0.50 D of emmetropia postoperatively. There were no differences in UDVA, CDVA, MRSE, or HOAs between groups (all P>.05). The UDVA was 20/20 or better in 85% of eyes in the wavefront-guided group and 86% of eyes in the wavefront-optimized group. All eyes had 20/25 or better CDVA postoperatively; no eye lost 2 lines of CDVA. Fourteen eyes were converted from wavefront-guided to wavefront-optimized treatment because of poor limbal ring alignment (8 eyes), a wave scan not consistent with the manifest refraction (5 eyes), and no iris registration (1 eye).

CONCLUSIONS

Wavefront-guided LASIK and wavefront-optimized LASIK produced equivalent visual outcomes and no differences in HOAs. Wavefront-guided treatment could not be performed in many eyes because of difficulties during wavefront measurement.