Ablation Profile Research Articles

Presbyopic Correction Using Monocular Bi-aspheric Ablation Profile (PresbyMAX) in Hyperopic Eyes: 1-Year Outcomes.

To present the 1-year outcomes of combining monocular bi-aspheric ablation profile and contralateral monofocal LASIK in hyperopic patients with presbyopia. In this retrospective case series, 36 consecutive patients (72 eyes) who underwent simultaneous bi-aspheric ablation (PresbyMAX: SCHWIND Eye-Tech-Solutions GmbH and Co KG, Kleinostheim, Germany) in the non-dominant eye and monofocal regular LASIK in the dominant eye for correction of hyperopia and presbyopia were reviewed for 1 year. Binocular uncorrected distance (UDVA), near (UNVA), corrected distance (CDVA), and distance corrected near (DCNVA) visual acuity and manifest refraction were analyzed postoperatively. At 1 year, the mean binocular UDVA improved significantly from 0.26 ± 0.25 to 0.039 ± 0.088 logMAR (P < .001). Binocular UNVA also improved from 0.73 ± 0.30 to 0.10 ± 0.22 logRAD (P < .001). Eighty-seven percent of patients achieved UDVA of 20/25 or better and 90% had UNVA of J3 or better. Simultaneous binocular distance and near vision of 20/25 and J2 or better was achieved in 70%. Only 17% of patients had a binocular DCNVA of J2 or better. No patient suffered from a loss of 2 lines of CDVA. Refractive stability was achieved for both eyes from 1 month postoperatively. The re-treatment rate was 14% for improvement of near vision within 6 months to 1 year. Presbyopic correction using monocular PresbyMAX combined with monofocal regular LASIK in the fellow eye is safe and acceptable in hyperopic patients. [J Refract Surg. 2017;33(1):37-43.].

Depth profiling of galvanoaluminium–nickel coatings on steel by UV- and VIS-LIBS

Laser-induced depth profiling was applied to the investigation of galvanised steel sheets as a typical modern multi-layer coating system for environmental corrosion protection. The samples were ablated stepwise by the use of two different wavelengths of a frequency-converted Nd:YAG-laser, 266nm and 532nm, with a pulse duration of τ=4ns at fluences ranging from F=50 to 250Jcm−2. The emission light of the resulting plasma was analysed as a function of both penetration depth and elemental spectrum in terms of linear correlation analysis. Elemental depth profiles were calculated and compared to EDX-cross sections of the cut sample. A proven mathematical algorithm designed for the reconstruction of layer structures from distorted emission traces caused by the Gaussian ablation profile can even resolve thin intermediate layers in terms of depth and thickness. The obtained results were compared to a purely thermally controlled ablation model. Thereby light-plasma coupling is suggested to be a possible cause of deviations in the ablation behaviour of Al. The average ablation rate h as a function of fluence F for Ni ranges from 1 to 3.5μm/pulse for λ=266nm as well as for λ=532nm. In contrast, the range of h for Al differs from 2 to 4μm/pulse for λ=532nm and 4 to 8μm/pulse for λ=266nm in the exact same fluence range on the exact same sample.

Changes to Corneal Aberrations and Vision After Monovision in Patients With Hyperopia After Using a Customized Aspheric Ablation Profile to Increase Corneal Asphericity (Q-factor).

To evaluate the visual outcomes and fourth-order Zernike spherical aberrations induced with a customized change in corneal asphericity (ΔQ) correction of presbyopia combined with monovision for hyperopic patients. Consecutive hyperopic patients who underwent presbyopic LASIK between September 2013 and July 2014 were included. For the non-dominant eyes, the aspheric ablation profile associated with a myopic refraction was planned using the Custom-Q nomogram (Alcon Laboratories, Inc., Fort Worth, TX). Uncorrected distance visual acuity (UDVA), uncorrected near visual acuity (UNVA), spherical equivalent refraction, ΔQ, and change in corneal spherical aberration coefficient (ΔC40) were analyzed. Postoperative data were collected at 1, 3, and 6 months. Sixty-five patients were included. The mean age was 56.5 ± 5.7 years (range: 47 to 70 years). At the 6-month follow-up, the spherical equivalent refraction for non-dominant and dominant eyes was -1.07 ± 0.74 and 0.32 ± 0.55 diopters (D), respectively. The mean binocular UDVA was 0.01 ± 0.04 logMAR (range: -0.12 to 0.30 logMAR); 91% of patients achieved 20/20 or better binocular UDVA and 83% of patients had Jaeger 3 (Parinaud 4) or better binocular UNVA. The ΔQ for non-dominant and dominant eyes was -0.61 ± 0.15 and -0.33 ± 0.25, respectively, for a 6-mm pupil diameter and was significantly higher for non-dominant eyes (P < .0001). The achieved ΔC40 was -0.49 ± 0.23 µm for non-dominant eyes (for a theoretical ideal value of -0.40 µm) and -0.30 ± 0.18 µm for dominant eyes. For non-dominant eyes, the attempted ΔQ (-0.60) was close to the achieved value (-0.61 ± 0.15). For hyperopic patients, combining the customized corneal aspheric ablation profile with monovision is safe, effective, and reproducible, inducing intended changes in corneal spherical aberrations. [J Refract Surg. 2016;32(11):734-741.].

Design of LTCC Based 3-D Antenna for Sub-THz Application

In the paper, selected aspects of LTCC technology for fabrication of passive elements for microwave application are presented. The research effect is based on the example of experimental 3-D antenna performed for a sub-THz scanner. For the described methods of antennas performance the achieved printing quality have been determined basing on observations using a digital microscope Hirox KH7700 and measurements of geometrical dimensions. The impact of geometrical structure dimensions and printed pattern resolution on its working abilities is also discussed. The main emphasis of the research work is on high resolution metallization obtainment by modification of screen printing parameters and conditions (the angle and pressure of squeegee, the mesh size), laser ablation and co-firing profile.

Femtosecond laser-assisted in situ keratomileusis multifocal ablation profile using a mini-monovision approach for presbyopic patients with hyperopia.

PurposeTo report the visual outcomes of the femtosecond laser-assisted multifocal aspheric corneal ablation profile using a mini-monovision approach and to evaluate if corneal multifocality was effective, and to report the relative benefits of this approach.Patients and methodsBilateral femtosecond laser-assisted in situ keratomileusis using a multifocal aspheric corneal ablation profile was performed on 19 hyperopic patients (38 eyes). They were divided into two groups based on eye dominance: dominant eye (DE) group targeting emmetropia and the nondominant eye (NDE) group targeting −0.5 D slight myopia. The uncorrected distance visual acuity (UDVA), uncorrected intermediate visual acuity (UIVA), uncorrected near visual acuity (UNVA), and retreatment rates were reported from baseline to 6 months.ResultsThe UNVA, UIVA, and UDVA improved significantly in both groups (Kruskal–Wallis test, DE and NDE: P<0.00001, P<0.000005, and P=0.00001, respectively). Corrected distance visual acuity (CDVA) baseline was better in both groups in comparison to UDVA at 6 months (Wilcoxon test, DE: P<0.001, 95% confidence interval (CI) of the median 0.0–0.0 LogMAR and 0.1000–0.1218 LogMAR and NDE: P=0.010, 95% CI of the median 0.0–0.0 LogMAR and 0.00–0.10 LogMAR). There was a significant loss of lines between CDVA baseline and UDVA at 6 months in both groups (DE group: 68% of eyes lost one line or more; NDE group: 58% of eyes lost one line or more). The corrected near visual acuity baseline compared to UNVA at 6 months was not statistically important (Wilcoxon test, DE: P=0.8125, 95% CI of the median 0.0–0.0 LogMAR and 0.0–0.0 LogMAR and NDE: P=0.82, 95% CI of the median 0.0–0.0 LogMAR and 0.0–0.0 LogMAR). The comparison among the UDVA, UIVA, and UNVA between the two groups at baseline and during all follow-ups was not statistically important. Two cases from the DE group were retreated (6%).ConclusionUse of this multifocal aspheric corneal ablation profile in patients with hyperopic presbyopia significantly improved UDVA, UIVA, and UNVA. This improvement was due to created multifocality of the cornea. The mini-monovision seems not to affect UDVA, UIVA, and UNVA between the two groups. The retreatment rates at the 6-month evaluation were significantly less in our study when compared with other studies. This method seems to improve UDVA, UIVA, and UNVA but could result in a significant statistical difference between CDVA baseline and UDVA at 6 months that leads to loss of lines in distance vision. Despite promising results, this is a preliminary evaluation of this new profile, and a larger number of eyes are needed to verify visual outcomes, retreatment rates, and safety.

Photorefractive keratectomy combined with corneal wavefront–guided and hyperaspheric ablation profiles to correct myopia

To evaluate the effects of photorefractive keratectomy (PRK) combined with corneal wavefront-guided ablation profiles and hyperaspheric ablation profiles on changes in higher-order aberrations (HOAs). Yonsei University College of Medicine and Eyereum Clinic, Seoul, South Korea. Comparative observational case series. Medical records of patients who had corneal wavefront-guided hyperaspheric PRK, corneal wavefront-guided mild-aspheric PRK, or non-corneal wavefront-guided mild-aspheric PRK were analyzed. The logMAR uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), and changes in corneal aberrations (root-mean-square [RMS] HOAs, spherical aberration, coma) were evaluated 1, 3, and 6months postoperatively. The records of 61 patients (96 eyes) were reviewed. There was no statistically significant difference in logMAR UDVA or MRSE between the 3 groups at any timepoint. Corneal RMS HOAs were significantly smaller in the corneal wavefront-guided hyperaspheric group and the corneal wavefront-guided mild-aspheric group than in the noncorneal wavefront-guided mild-aspheric group at each timepoint. Corneal spherical aberration was significantly smaller for corneal wavefront-guided hyperaspheric PRK than for noncorneal wavefront-guided mild-aspheric PRK 6months postoperatively. Changes in corneal spherical aberration (preoperatively and 6months postoperatively) in corneal wavefront-guided hyperaspheric PRK were significantly smaller than in corneal wavefront-guided mild-aspheric PRK (P=.046). Corneal coma was significantly smaller with corneal wavefront-guided hyperaspheric PRK and corneal wavefront-guided mild-aspheric PRK than with noncorneal wavefront-guided mild-aspheric PRK 3months and 6months postoperatively. Corneal wavefront-guided hyperaspheric PRK induced less corneal spherical aberration 6months postoperatively than corneal wavefront-guided mild-aspheric PRK and noncorneal wavefront-guided mild-aspheric PRK. None of the authors has a financial or proprietary interest in any material or method mentioned.

Outcomes of excimer laser enhancements in pseudophakic patients with multifocal intraocular lens.

PurposeThe aim of this study was to assess visual and refractive outcomes of laser vision correction (LVC) to correct residual refraction after multifocal intraocular lens (IOL) implantation.Patients and methodsIn this retrospective study, 782 eyes that underwent LVC to correct unintended ametropia after multifocal IOL implantation were evaluated. Of all multifocal lenses implanted during primary procedure, 98.7% were refractive and 1.3% had a diffractive design. All eyes were treated with VISX STAR S4 IR excimer laser using a convectional ablation profile. Refractive outcomes, visual acuities, patient satisfaction, and quality of life were evaluated at the last available visit.ResultsThe mean time between enhancement and last visit was 6.3±4.4 months. Manifest spherical equivalent changed from −0.02±0.83 D (−3.38 D to +2.25 D) pre-enhancement to 0.00±0.34 D (−1.38 D to +1.25 D) post-enhancement. At the last follow-up, the percentage of eyes within 0.50 D and 1.00 D of emmetropia was 90.4% and 99.5%, respectively. Of all eyes, 74.9% achieved monocular uncorrected distance visual acuity 20/20 or better. The mean corrected distance visual acuity remained the same before (−0.04±0.06 logMAR [logarithm of the minimum angle of resolution]) and after LVC procedure (−0.04±0.07 logMAR; P=0.70). There was a slight improvement in visual phenomena (starburst, halo, glare, ghosting/double vision) following the enhancement. No sight-threatening complications related to LVC occurred in this study.ConclusionLVC in pseudophakic patients with multifocal IOL was safe, effective, and predictable in a large cohort of patients.

Corneal-Wavefront guided transepithelial photorefractive keratectomy after corneal collagen cross linking in keratoconus

PurposeTo evaluate the efficacy and safety of Corneal-Wavefront guided transepithelial photorefractive keratectomy (TransPRK) after corneal collagen cross linking (CXL) in keratoconic patients. MethodsIn this retrospective, non-comparative, consecutive case series, 39 keratoconic eyes underwent Corneal-Wavefront guided TransPRK for the correction of aberrations at least 4 months after conventional CXL at SEKAL Rovigo Microsurgery Centre, Rovigo, Italy. Two eyes (5%) underwent a secondary laser retreatment for the improvement of post-operative visual acuity and were not included in this retrospective analysis. The mean age of the patients was 35±12 years (19–64 years) at the time of the surgery. Keratron-Scout (Optikon) topographer was used for diagnostic tests and a flying-spot laser (AMARIS; SCHWIND eye-tech-solutions) was used for the refractive surgery. Complete ophthalmic examinations were performed before and after the surgery (4–36 months postoperatively with a mean follow up time of 10±8 months). ResultsPreoperatively, eyes showed irregular astigmatism up to 8D. At last postoperative follow-up, 21 eyes (57%) had UDVA better than 20/40, and six eyes (16%) had UDVA of 20/20. Twenty-three eyes (62%) were within 1.50D of attempted correction in spherical equivalent (mean deviation from target was +1.09±2.36D, range −2.50 to +7.38D). No eye lost 2 Snellen lines of CDVA, and 15 eyes (41%) had an increase of more than 2 lines. ConclusionsCorneal-Wavefront guided transepithelial PRK ablation profiles after conventional CXL yields to good visual, optical, and refractive results. These treatments are safe and efficacious for the correction of refracto-therapeutic problems in keratoconic patients.

Ultrafast laser spatial beam shaping based on Zernike polynomials for surface processing

In femtosecond laser machining, spatial beam shaping can be achieved with wavefront modulators. The wavefront modulator displays a pre-calculated phase mask that modulates the laser wavefront to generate a target intensity distribution in the processing plane. Due to the non-perfect optical response of wavefront modulators, the experimental distribution may significantly differ from the target, especially for continuous shapes. We propose an alternative phase mask calculation method that can be adapted to the phase modulator optical performance. From an adjustable number of Zernike polynomials according to this performance, a least square fitting algorithm numerically determines their coefficients to obtain the desired wavefront modulation. We illustrate the technique with an optically addressed liquid-crystal light valve to produce continuous intensity distributions matching a desired ablation profile, without the need of a wavefront sensor. The projection of the experimental laser distribution shows a 5% RMS error compared to the calculated one. Ablation of steel is achieved following user-defined micro-dimples and micro-grooves targets on mold surfaces. The profiles of the microgrooves and the injected polycarbonate closely match the target (RMS below 4%).

A numerical study of isotropic and anisotropic ablation in MCCI by MPS method

Anisotropic and isotropic ablation in molten corium-concrete interaction (MCCI) phenomenon was studied with the Moving Particle Semi-implicit (MPS) method by carrying out numerical simulations of CCI-2 and 3 experiments. The interaction of the fully oxidized PWR core melts with specially-designed two-dimensional limestone and siliceous concrete test sections was analyzed, focusing on investigating the two-dimensional ablation behavior with both limestone and siliceous concrete. The phase transition of molten corium and concrete was modeled based on a phase transition model for mixture. Slag film model and crust dissolution models were incorporated in the current MPS code to simulate the effect of gas generation and crust dissolution phenomena in limestone concrete. The effects of gas generation and aggregates on the concrete ablation behavior were investigated by simulating different specially designed cases. The simulation results by MPS method reproduced the isotropic and anisotropic cavity ablation profile and the overall axial and lateral ablation rates agreed well with the experimental measures. The experimental and MPS results both indicate that the crust on the corium-concrete interface can play an important part in concrete ablation process. The simulation results by MPS method also provide evidence to support the theory that aggregates are part of the cause of anisotropic ablation profile in cavity with siliceous concrete because aggregates could delay the axial basemat ablation more significantly than the lateral one and influence the power split in the melt pool.

Numerical simulation of 2D ablation profile in CCI-2 experiment by moving particle semi-implicit method

Numerous experiments have been performed to explore the mechanisms of molten core-concrete interaction (MCCI) phenomena since the 1980s. However, previous experimental results show that uncertainties pertaining to several aspects such as the mixing process and crust behavior remain. To explore the mechanism governing such aspects, as well as to predict MCCI behavior in real severe accident events, a number of simulation codes have been developed for process calculations. However, uncertainties exist among the codes because of the use of different empirical models. In this study, a new computational code is developed using multiphysics models to simulate MCCI phenomena based on the moving particle semi-implicit (MPS) method. Momentum and energy equations are used to solve the velocity and temperature fields, and multiphysics models are developed on the basis of the basic MPS method. The CCI-2 experiment is simulated by applying the developed code. With respect to sidewall ablation, good agreement is observed between the simulation and experimental results. However, axial ablation is slower in the simulation, which is probably due to the underestimation of the enhancement effect of heat transfer provided by the moving bubbles at the bottom. In addition, the simulation results confirm the rapid erosion phenomenon observed in the experiment, which in the numerical simulation is explained by solutal convection provided by the liquid concrete at the corium/concrete interface. The results of the comparison of different model combinations show the effect of each multiphysics model on ablation behavior.

Multifocal corneal ablation (Supracor) in hyperopic presbyopia: 1-year results in a cross-sectional study.

To evaluate the efficacy and safety of the multifocal excimer laser corneal ablation profile (the Supracor procedure) in hyperopic presbyopia 1 year after laser treatment. This prospective, consecutive, one-center, cross-sectional study included 20 patients with hyperopic presbyopia 1 year after treatment with the Supracor procedure. The main outcome measures were monocular uncorrected distance visual acuity (UDVA) and uncorrected near visual acuity (UNVA), photopic contrast sensitivity (Pelli-Robson charts), patient satisfaction, and functioning at 12 months. Thirty-nine eyes of 20 patients (mean age 59 ± 7.2 years) were treated. Mean UDVA improved from 0.56 ± 0.31 (mean 0.34 logMAR) preoperatively to 0.9 ± 0.15 (mean 0.06 logMAR) 12 months after surgery. Mean UNVA increased from 0.15 ± 0.07 (mean 0.84 logMAR) before surgery to 0.62 ± 0.24 (mean 0.23 logMAR) 12 months after treatment. Four eyes lost 2 lines of corrected distance visual acuity (10.3%). Monocular photopic contrast sensitivity was within age-correlated normal range (Pelli-Robson chart, mean contrast sensitivity 1.83 ± 0.18). A total of 75% of the patients would undergo Supracor again (1 not, 4 perhaps). The most frequently reported side effects were increased glare, reduced distance vision, and fluctuations in vision. Most patients used artificial tears. One year after Supracor, UDVA and UNVA improved markedly, photopic contrast sensitivity was in normal age-correlated range, and the majority of patients (75%) was satisfied with the results. Side effects like loss of distance vision, fluctuations of vision, and increased glare have a greater influence on patient satisfaction than the improvement of spectacle-free near vision.

Simulated effect of aspheric transition zone ablation profiles on optical aberrations after customized myopia ablation

PurposeTo understand and study the effect of transition zone on wavefront aberrations after laser refractive surgery is important for improving visual correction outcomes. MethodsBased on the ablation profiles of optical zone and aspheric transition zone for wavefront-guided refractive surgery, the influence of aspheric transition zone on the induced wavefront aberrations was studied. ResultsThe types of ablation profile of aspheric transition zone had a significant influence on the induced higher-order wavefront aberrations. The induced aberrations were mainly spherical aberration and coma. In addition, the profile #9 showed that the induced spherical aberration had a lower RMS value than that in other profiles and yet the induced secondary astigmatism was relatively larger. Furthermore, secondary spherical aberration in the profile #9 was slightly lower than that in other profiles. ConclusionThe residual higher order aberrations may be decreased by creating an optimized transition zone and may be result in improving postoperative visual performance, but they cannot be eliminated.

Optical Profile Following High Hyperopia Correction With a 500-Hz Excimer Laser System.

To evaluate corneal higher order aberrations after LASIK for the correction of high hyperopia using a 500-Hz excimer laser and optimized ablation profile. Retrospective consecutive study including 51 eyes of 28 patients (age range: 21 to 54 years) with high hyperopia or hyperopic astigmatism (sphere ≥ 5.00 diopters). All cases underwent LASIK using the sixth generation Amaris excimer laser (SCHWIND eye-tech-solutions, Kleinostheim, Germany) and a femtosecond laser platform for flap creation. Postoperative changes in corneal higher order aberrations for the 4-, 5-, and 6-mm pupil diameters and corneal asphericity for 4.5 and 8 mm were represented at the end of the 6-month follow-up. A significant increase in corneal root mean square higher order, spherical, and coma aberrations was observed 6 months after surgery (P < .01). Corneal asphericity for the 4.5-mm (Q45) and 8-mm (Q8) corneal diameter also changed significantly during the postoperative period (P < .01). Strehl ratio change was not statistically significant (P = .77). Correction of high hyperopia with LASIK significantly induces corneal higher order aberrations regardless of the physiologic level of photopic and mesopic pupil conditions.

Corneal Surgical Approach in the Treatment of Presbyopia

Purpose: The aim of this paper is to outline the various corneal approaches to the treatment of presbyopia and discuss their effectiveness Method: Most corneal surgical procedures involve LASIK. Supracor uses a progressive ablation profile to provide an aberration optimized smooth transition from distance to near correction. In presbyLASIK a hyper positive area is created at the centre of the cornea for near vision and the periphery provides a focus for distance. The Intracor procedure is an intra-stromal treatment using a femto-second laser. It creates concentric rings with the stroma. These bring about central steepening of the cornea. Monovision corrects one eye for distance and the less dominant eye for near. Conductive keratoplasty uses heat generated by high radio frequency current to alter the corneal stroma. Corneal small aperture implants or inlays are inserted into the cornea through a pocket created by femtosecond laser to improve the near and intermediate vision. Results: Supracor offers the best prospect but the high retreatment rate is a major drawback. Intracor and corneal inlays offer the best hope for elimination of reading glasses but reduction of distance vision, loss of binocularity and reduction of the effect overtime limit their use. Monovision for a selective group of patient is still the best alternative. Conclusions: There is no ideal corneal surgical approach to presbyopia. The future may involve more than one approach, perhaps a corneal approach for patients under 50 and a lens solution for older patient. The ideal procedure and best outcome is still some way off.

Corneal higher-order aberrations and higher-order Strehl ratio after aberration-free ablation profile to treat compound myopic astigmatism

To evaluate the changes in corneal higher-order aberrations (HOAs) and their impact on corneal higher-order Strehl ratio after aberration-free ablation profile. Verter Institute, H. Olhos, São Paulo, Brazil. Prospective interventional study. Eyes that had aberration-free myopic ablation were divided into 3 groups, based on the spherical equivalent (SE). The corneal HOAs and higher-order Strehl ratios were calculated before surgery and 3 months after surgery. The postoperative uncorrected-distance visual acuity, corrected-distance visual acuity, and SE did not present statistical differences among groups (88 eyes, P > .05). For a 6 mm pupil, the corneal HOA showed a mean increase of 0.17 μm (range 0.39 to 0.56 μm) (P < .001) and the corneal higher-order Strehl ratio presented a reduction of 0.03 (from 0.25 to 0.22) (P = .001). The following consistent linear predictive model was obtained: corneal HOA induction = 1.474 - 0.032 × SE - 0.225 × OZ, where OZ is the optical zone (R(2) = 0.49, adjusted R(2) = 0.48, P < .001). The corneal HOAs and the higher-order Strehl ratios deteriorated after moderate and high myopic ablations. The worsening in corneal aberrations and optical quality were related to the magnitude of the intended correction and did not affect high-contrast visual performance. The OZ was the only modifiable parameter capable to restrain the optical quality loss. The author has no financial or proprietary interest in any material or method mentioned.

Control of Induced Spherical Aberration in Moderate Hyperopic LASIK by Customizing Corneal Asphericity.

To compare differences in induced aberrations and visual acuity after wavefront-optimized LASIK and aspheric-customized LASIK for the treatment of hyperopia. Forty consecutive eyes underwent uneventful LASIK for treatment of moderate hyperopia (+3.82 ± 0.63 diopters [D] [+2.75; +5.125]). A standard procedure was performed in the wavefront-optimized LASIK group (n = 24), whereas a postoperative Q-factor equal to zero was scheduled in the aspheric-customized LASIK group (n = 16). At 6 months, mean spherical aberration for a 6-mm pupil diameter was -0.39 ± 0.23 µm (range: -0.76 to 0.01 µm) and Q-factor was -0.52 ± 0.22 (range: -1.00 to -0.12 µm) in the wavefront-optimized group and 0.04 ± 0.18 µm (range: -0.34 to 0.29 µm) and -0.04 ± 0.25 (range: -0.64 to 0.40 µm) in the aspheric-customized LASIK group (P ≤ .05). All remaining outcomes showed no significant differences between groups. UDVA was 20/18.69 ± 0.15 (range: 0.80 to 1.20) in the wavefront-optimized LASIK group and 20/20 ± 0.17 (range: 0.50 to 1.20) in the aspheric-customized LASIK group. One patient in the wavefront-optimized LASIK group lost two or more lines of CDVA and no lines were lost in the aspheric-customized LASIK group. The results in this small cases series suggest that using an aspheric-customized ablation profile with a target Q-factor equal to 0 in moderate hyperopic LASIK is statistically compatible with a diminishing induced spherical aberration without altering procedural safety when the WaveLight Allegretto 400-Hz excimer laser platform (Alcon Laboratories, Inc., Fort Worth, TX) is used.

Flap lift and photorefractive keratectomy enhancements after primary laser in situ keratomileusis using a wavefront-guided ablation profile: Refractive and visual outcomes

To analyze results of wavefront-guided laser vision correction retreatments performed either by lifting the original flap or by surface ablation over the flap. Optical Express, Glasgow, United Kingdom. Retrospective case series. This retrospective study included patients grouped according to whether they had flap lift enhancement or photorefractive keratectomy (PRK) performed over the LASIK flap. All retreatment procedures were performed with the Visx Star S4 IR excimer laser with wavefront-guided ablation profile derived from the iDesign aberrometer. Visual acuities, refractive outcomes, vector analysis of refractive cylinder and complications were analyzed in this study. The results of the last available clinical visit are presented. This retrospective study included 290 eyes of 202 patients divided into 2 groups: 119 eyes that had flap lift enhancement (Group A), and 171 eyes in which photorefractive keratectomy (PRK) was performed over the LASIK flap (Group B). The mean follow-up was 4.0 ± 1.9 months in Group A and 4.2 ± 1.6 in Group B. The mean postoperative manifest spherical equivalent was -0.01 ± 0.35 D and +0.06 ± 0.39 D in Groups A and B, respectively. The percentage of eyes with postenhancement UDVA 20/20 or better was 87.4% in Group A and 79.5 % in Group B (P = .09). In Group A, 22 eyes (18.5%) developed epithelial ingrowth, of which surgical intervention was required in 2 eyes (1.7%). Grade 1 or less haze was noted in 9 (5.3%) eyes in Group B, and resolved in all cases within the first 6 postoperative months. Both retreatment techniques were considered to be effective, predictable, and safe. Steven C Schallhorn MD is a consultant to Abbott Medical Optics and Zeiss, and Global Medical Director for Optical Express. None of the other authors have a financial or proprietary interest in the products and materials presented in this paper.

Comparison of femtosecond laser small-incision lenticule extraction and laser-assisted subepithelial keratectomy to correct myopic astigmatism

To compare the efficacy of correcting myopic astigmatism with femtosecond laser small-incision lenticule extraction (SMILE, Carl Zeiss Meditec AG) versus laser-assisted subepithelial keratectomy (LASEK). The study was conducted at the Ophthalmology Department, Eye and ENT Hospital, Shanghai, China. A retrospective, cross-sectional study. This study included patients who underwent small-incision lenticule extraction or LASEK for the correction of myopia and myopic astigmatism. Preoperative and 6-month postoperative astigmatism values were analyzed. The efficacies of the 2 surgeries to correct astigmatism were compared. A total of 180 right eyes of 180 patients (small-incision lenticule extraction: n = 113, LASEK: n = 67) were included. No significant difference was found between the 2 groups in the preoperative astigmatism (small-incision lenticule extraction: 1.16 ± 0.85D, LASEK: 1.16 ± 0.83D, P > .05) or the postoperative astigmatism (small-incision lenticule extraction: 0.35 ± 0.37D; LASEK: 0.31 ± 0.42D, P > .05), determined by manifest refraction. No significant difference was found between the 2 groups in surgically induced astigmatism vector (small-incision lenticule extraction: 1.13 ± 0.83D, LASEK: 1.01 ± 0.65D, P > .05). The correction index was higher for the small-incision lenticule extraction group (1.05 ± 0.53) than for the LASEK group (0.95 ± 0.21, P = .045). The postoperative astigmatism was significantly higher for the small-incision lenticule extraction group when the preoperative astigmatism was 1.0 D or less (small-incision lenticule extraction: 0.26 ± 0.30D, LASEK: 0.12 ± 0.20D, P = .007) and lower for the small-incision lenticule extraction group when the preoperative astigmatism was more than 2.0 D (small-incision lenticule extraction: 0.48 ± 0.37D, LASEK: 0.89 ± 0.46D, P = .002). An adjustment of nomograms for correcting low astigmatism (≤1.0 D) by small-incision lenticule extraction is suggested due to the tendency toward overcorrection, whereas a nomogram adjustment for tissue-saving ablation profile is needed for the correction of high astigmatism (>2.0 D) by LASEK due to the tendency toward undercorrection. The authors declare that they have no competing financial interests.

Risk factors of regression and undercorrection in photorefractive keratectomy: a case-control study.

To determine risk factors of regression and undercorrection following photorefractive keratectomy (PRK) in myopia or myopic astigmatism. A case-control study was designed in which eyes with an indication for re-treatment (RT) were defined as cases; primary criteria for RT indication, as assessed at least 9mo postoperatively, included an uncorrected distance visual acuity (UDVA) of 20/30 or worse and a stable refraction for more than 3mo. Additional considerations included optical quality symptoms and significant higher order aberrations (HOAs). Controls were chosen from the same cohort of operated eyes which had complete post-operative follow up data beyond 9mo and did not need RT. The cohort included patients who had undergone PRK by the Tissue-Saving (TS) ablation profile of Technolas 217z100 excimer laser (Bausch & Lomb, Rochester, NY, USA). Mitomycin C had been used in all of the primary procedures. We had 70 case eyes and 158 control eyes, and they were comparable in terms of age, sex and follow-up time (P values: 0.58, 1.00 and 0.89, respectively). Pre-operative spherical equivalent of more than -5.00 diopter (D), intended optical zone (OZ) diameter of less than 6.00 mm and ocular fixation instability during laser ablation were associated with RT indications (all P values <0.001). These factors maintained their significance in the multiple logistic regression model with odd ratios of 6.12, 6.71 and 7.89, respectively. Higher refractive correction (>-5.00 D), smaller OZ (<6.00 mm) and unstable fixation during laser ablation of PRK for myopia and myopic astigmatism were found to be strong predictors of undercorrection and regression.