Equivalent Correction Research Articles

Fractionally Integrated Data and the Autodistributed Lag Model: Results from a Simulation Study

Two contributions in this issue, Grant and Lebo and Keele, Linn, and Webb, recommend using an ARFIMA model to diagnose the presence of and estimate the degree of fractional integration, then either (i) fractionally differencing the data before analysis or, (ii) for cointegrated variables, estimating a fractional error correction model. But Keele, Linn, and Webb also present evidence that ARFIMA models yield misleading indicators of the presence and degree of fractional integration in a series with fewer than 1000 observations. In a simulation study, I find evidence that the simple autodistributed lag model (ADL) or equivalent error correction model (ECM) can, without first testing or correcting for fractional integration, provide a useful estimate of the immediate and long-run effects of weakly exogenous variables in fractionally integrated (but stationary) data.

Gas Chromatography Coupled to Atmospheric Pressure Chemical Ionization FT-ICR Mass Spectrometry for Improvement of Data Reliability

Atmospheric pressure chemical ionization (APCI) offers the advantage of molecular ion information with low fragmentation. Hyphenating APCI to gas chromatography (GC) and ultrahigh resolution mass spectrometry (FT-ICR MS) enables an improved characterization of complex mixtures. Data amounts acquired by this system are very huge, and existing peak picking algorithms are usually extremely time-consuming, if both gas chromatographic and ultrahigh resolution mass spectrometric data are concerned. Therefore, automatic routines are developed that are capable of handling these data sets and further allow the identification and removal of known ionization artifacts (e.g., water- and oxygen-adducts, demethylation, dehydrogenation, and decarboxylation). Furthermore, the data quality is enhanced by the prediction of an estimated retention index, which is calculated simply from exact mass data combined with a double bond equivalent correction. This retention index is used to identify mismatched elemental compositions. The approach was successfully tested for analysis of semivolatile components in heavy fuel oil and diesel fuel as well as primary combustion particles emitted by a ship diesel research engine. As a result, 10-28% of the detected compounds, mainly low abundant species, classically assigned by using only the mass spectrometric information, were identified as not valid and removed. Although GC separation is limited by the slow acquisition rate of the FT-ICR MS (<1 Hz), a database driven retention time comparison, as commonly used for low resolution GC/MS, can be applied for revealing isomeric information.

Grid of theoretical NLTE equivalent widths of four Ba ii lines and barium abundance in cool stars

We present a grid of computed non-local thermodynamic equilibrium (NLTE) equivalent widths (EW) and NLTE abundance corrections for four Ba II lines: 4554, 5853, 6141, and 6496 A. The grid can be useful in deriving the NLTE barium abundance in stars having parameters in the following ranges: effective temperature from 4000 K to 6500 K, surface gravity log g from 0 to 5, microturbulent velocity 0 km s^-1 to 3 km s^-1, metallicity [Fe/H] from -2 to +0.5, and [Ba/Fe] from -0.4 to +0.6. The NLTE abundance can be either derived by EW interpolation (using the observed Ba II line EW) or by using the NLTE correction applied to a previously determined LTE abundance. Ba II line equivalent widths and the NLTE corrections were calculated using the updated MULTI code and the Ba II atomic model that was previously applied to determine the NLTE barium abundance in different types of stars. The grid is available on-line through the web, and we find that the grid Ba NLTE corrections are almost as accurate as direct NLTE profile fitting (to within 0.05-0.08 dex). For the weakest Ba II line (5853 A) the LTE abundances almost agree with the NLTE abundances, whereas the other three Ba II lines, 4554, 6141, and 6496 A, need NLTE corrections even at the highest metallicities tested here. The 4554 A line is extremely strong and should not be used for abundance analysis above [Fe/H]= -1. Furthermore, we tested the impact of different model atmospheres and spectrum synthesis codes and found average differences of 0.06 dex and 0.09 dex, respectively, for all four lines. At these metallicities we find an average Delta NLTE of +/-0.1 dex for the three useful Ba lines for subsolar cool dwarfs.

Demonstrating correction of low levels of astigmatism with realistic scenes.

Modern standard visual acuity tests are primarily designed as diagnostic tools for use during subjective refraction and normally bear little relation to real-world situations. We have developed a methodology to create realistic rendered scenes that demonstrate potential vision improvement in a relevant and engaging way. Low-cylindrical refractive error can be made more noticeable by optimizing the contrast and spatial frequencies, and by testing four different visual perception skills: motion tracking, pattern recognition, visual clutter differentiation and contrast sensitivity. Using a 1.00DC lens during iteration, we created a range of still and video scenes before optimizing to a selection 3-D rendered street scenes. These were assessed on everyday relevance, emotional and visual engagement and sensitivity to refractive correction for low-cylinder astigmats (0.75-1.00DC, n=74) wearing best spherical equivalent correction and then with astigmatism corrected. The most promising visual elements involved or combined optimized textures, distracting patterns behind text, faces at a distance, and oblique text. 91.9% of subjects (95% CI: 83.2, 97.0) reported an overall visual improvement when viewing the images with astigmatic correction, and 96% found the images helpful to determine which type of contact lens to use. Our method, which combines visual science with design thinking, takes a new approach to creating vision tests. The resultant test scenes can be used to improve patient interaction and help low cylinder astigmats see relevant, every-day benefits in correcting low levels (0.75 & 1.00DC) of astigmatism.

Comparison of prophylactic higher fluence corneal cross-linking to control, in myopic LASIK, one year results.

PurposeTo compare 1-year results: safety, efficacy, refractive and keratometric stability, of femtosecond myopic laser-assisted in situ keratomileusis (LASIK) with and without concurrent prophylactic high-fluence cross-linking (CXL) (LASIK-CXL).MethodsWe studied a total of 155 consecutive eyes planned for LASIK myopic correction. Group A represented 73 eyes that were treated additionally with concurrent prophylactic high-fluence CXL; group B included 82 eyes subjected to the stand-alone LASIK procedure. The following parameters were evaluated preoperatively and up to 1-year postoperatively: manifest refractive spherical equivalent (MRSE), refractive astigmatism, visual acuity, corneal keratometry, and endothelial cell counts. We plotted keratometry measurements pre-operatively and its change in the early, interim and later post-operative time for the two groups, as a means of keratometric stability comparison.ResultsGroup A (LASIK-CXL) had an average postoperative MRSE of −0.23, −0.19, and −0.19 D for the 3-, 6-, and 12-month period, respectively, compared to −6.58±1.98 D preoperatively. Flat keratometry was 37.69, 37.66, and 37.67 D, compared to 43.94 D preoperatively, and steep keratometry was 38.35, 38.36, and 38.37 D, compared to 45.17 D preoperatively. The predictability of Manifest Refraction Spherical Equivalent (MRSE) correction showed a correlation coefficient of 0.979. Group B (stand-alone LASIK) had an average postoperative MRSE of −0.23, −0.20, and −0.27 D for the 3-, 6-, and 12-month period, respectively, compared with −5.14±2.34 D preoperatively. Flat keratometry was 37.65, 37.89, and 38.02 D, compared with 43.15 D preoperatively, and steep keratometry was 38.32, 38.57, and 38.66 D, compared with 44.07 D preoperatively. The predictability of MRSE correction showed a correlation coefficient of 0.970. The keratometric stability plots were stable for the LASIK CXL group and slightly regressing in the standard LASIK group, a novel stability evaluation metric that may escape routine acuity and refraction measurements.ConclusionApplication of prophylactic CXL concurrently with myopic LASIK surgery appears to contribute to improved refractive and keratometric stability compared to standard LASIK. The procedure appears safe and provides a new potential for LASIK correction.

Novel evaluation method of fuel consumption and emission for heavy-duty hybrid electric vehicles

This paper is a continuation of a previous paper titled “A novel way to calculate energy efficiency for rechargeable batteries” published on Journal of Power Sources/2012 describing a new method to calculate energy efficiency for rechargeable batteries. The present paper further describes the application of energy efficiency model on the evaluation of fuel consumption and emission for the heavy-duty hybrid electric vehicles (HD-HEVs). A more accurate calculation method of net energy change for power battery pack is proposed based on energy efficiency model of power battery pack. A more simplified and accurate correction method of fuel consumption and emission is also presented based on equivalent mileage. The fuel consumption and emission on chassis dynamometer are measured in the HD-HEVs. The experiment results show that relative errors of fuel consumption and emission between equivalent mileage correction results and linear regression correction results are less than 3%, which verifies accuracy and validates the proposed evaluation method for HD-HEVs fuel consumption and emission.

Braces Optimized With Computer-Assisted Design and Simulations Are Lighter, More Comfortable, and More Efficient Than Plaster-Cast Braces for the Treatment of Adolescent Idiopathic Scoliosis

Study DesignFeasibility study to compare the effectiveness of 2 brace design and fabrication methods for treatment of adolescent idiopathic scoliosis: a standard plaster-cast method and a computational method combining computer-aided design and fabrication and finite element simulation. ObjectivesTo improve brace design using a new brace design method. Summary of Background DataInitial in-brace correction and patient's compliance to treatment are important factors for brace efficiency. Negative cosmetic appearance and functional discomfort resulting from pressure points, humidity, and restriction of movement can cause poor compliance with the prescribed wearing schedule. MethodsA total of 15 consecutive patients with brace prescription were recruited. Two braces were designed and fabricated for each patient: a standard thoracolumbo-sacral orthosis brace fabricated using plaster-cast method and an improved brace for comfort (NewBrace) fabricated using a computational method combining computer-aided design and fabrication software (Rodin4D) and a simulation platform. Three-dimensional reconstructions of the torso and the trunk skeleton were used to create a personalized finite element model, which was used for brace design and predict correction. Simulated pressures on the torso and distance between the brace and patient's skin were used to remove ineffective brace material situated at more than 6 mm from the patient's skin. Biplanar radiographs of the patient wearing each brace were taken to compare their effectiveness. Patients filled out a questionnaire to compare their comfort. ResultsNewBraces were 61% thinner and had 32% less material than standard braces with equivalent correction. NewBraces were more comfortable (11 of 15 patients) or equivalent to (4 of 15 cases) standard braces. Simulated correction was simulated within 5° compared with in-brace results. ConclusionsThis study demonstrates the feasibility of designing lighter and more comfortable braces with correction equivalent to standard braces. This design platform has the potential to further improve brace correction efficiency and its compliance.

Panoptes: Calibration of a dosimetry system for eye brachytherapy

Intraocular cancer is a serious threat to the lives of those that suffer from it. Dosimetry for eye brachytherapy presents a significant challenge due to the inherently steep dose gradients that are needed to treat such small tumours in close proximity to sensitive normal structures. This issue is addressed by providing much needed quality assurance to eye brachytherapy, a novel volumetric dosimetry system, called Panoptes was developed. This study focuses on the preliminary characterisation and calibration of the system. Using ion beam facilities, the custom, pixelated silicon detector of Panoptes was shown to have good charge collection uniformity and a well defined sensitive volume. Flat-field calibration was conducted on the device using a 250 kVp orthovoltage beam. Finally, the detector and phantom were simulated with Monte Carlo in Geant4, to create water equivalent dose correction factors for each pixel across a range of angles.

Visual and Refractive Outcomes of Femtosecond Lenticule Extraction and Small-Incision Lenticule Extraction for Myopia

To compare the visual and refractive outcomes of femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE) in eyes with myopia. Prospective, randomized, masked clinical trial with intraindividual comparison. This study evaluated 52 eyes of 26 consecutive patients with spherical equivalents of -4.19 ± 1.65 diopters (D) (mean ± standard deviation) who underwent FLEx in 1 eye and SMILE in the other eye by randomized assignment. Before surgery, and 1 week and 1, 3, and 6 months after surgery, we assessed safety, efficacy, predictability, stability, and adverse events of the 2 surgical techniques. LogMAR uncorrected and corrected distance visual acuity was, respectively, -0.17 ± 0.10, -0.20 ± 0.07 in the FLEx group and -0.15 ± 0.10, -0.19 ± 0.07 in the SMILE group 6 months postoperatively. In the FLEx and SMILE groups 6 months postoperatively, 96% and 100% of eyes, respectively, were within 0.5 D of the targeted spherical equivalent correction. Changes of -0.02 ± 0.39 D and 0.00 ± 0.30 D occurred in manifest refraction from 1 week to 6 months in the FLEx and SMILE groups, respectively. No clinically significant complications occurred in the FLEx or the SMILE group. Both FLEx and SMILE performed well in the correction of myopia throughout the 6-month observation period. FLEx may be essentially equivalent to SMILE in terms of safety, efficacy, predictability, and stability, suggesting that the presence or absence of lifting the flap does not significantly affect these visual and refractive outcomes.

Refractive and Keratometric Stability in High Myopic LASIK With High-Frequency Femtosecond and Excimer Lasers

To evaluate safety, efficacy, ergonomy, and refractive and keratometric stability in high myopia LASIK procedures using a novel femtosecond and excimer laser surgery platform. One hundred sixteen eyes in consecutive cases of high myopic LASIK ( ≥ -6.00 diopters [D]) with the Alcon-WaveLight FS200 femtosecond and EX500 excimer lasers (Alcon Laboratories, Fort Worth, TX) were evaluated preoperatively and postoperatively for the following parameters: refractive error, corrected distance visual acuity, uncorrected distance visual acuity, spherical equivalent correction, keratometry (with Placido topography and Scheimpflug tomography), and refractive astigmatism. Average follow-up time was 6.2 months (range: 3 to 12 months). Postoperative average refractive error was -0.37, -0.43, and -0.25 D for the 3-, 6-, and 12-month period, compared to -7.67 ± 1.55 D preoperatively. At 3, 6, and 12 months postoperatively 94%, 96.3%, and 100% of eyes, respectively, were within 1.0 D defocus equivalent. Postoperative refractive astigmatism was -0.21, -0.21, -0.13 D for the 3-, 6-, and 12-month period compared to -1.07 ± 1.91 D preoperatively. The proportion of eyes with postoperative astigmatism within 0.25 D was 85.3%, 81.5%, and 100%, for the 3-, 6-, and 12-month visit, respectively. Keratometric stability was within 0.22 D after the 12-month visit. There was no epithelial ingrowth or diffuse lamellar keratitis in any case. Clinical outcomes with this technique and technology appear to be promising in high level uncorrected visual rehabilitation of high myopia. There was small regression potential in the sample evaluated.

LargeNcdeconfinement transition in the presence of a magnetic field

We investigate the effect of a homogeneous magnetic field on the thermal deconfinement transition of QCD in the large ${N}_{c}$ limit. First we discuss how the critical temperature decreases due to the inclusion of ${N}_{f}\ensuremath{\ll}{N}_{c}$ flavors of massless quarks in comparison to the pure glue case. Then we study the equivalent correction in the presence of an external Abelian magnetic field. To leading order in ${N}_{f}/{N}_{c}$, the deconfinement critical temperature decreases with the magnetic field if the flavor contribution to the pressure behaves paramagnetically, with a sufficiently large magnetization as to overcome any possible magnetic effects in the string tension. Finally, we discuss the effects from a finite quark mass and its competition with magnetic effects.

Short Fusion Strategy for Lenke Type 1 Thoracic Curve Using Pedicle Screw Fixation

A retrospective case-control study Short fusion using pedicle screws (PSs) with an attempt to attain maximum correction of the main thoracic curve was conducted for patients with a Lenke type 1 curve, to prevent postoperative left shoulder elevation. The outcomes were compared with those of conventional surgery. Excessive correction of the main thoracic curve by PSs causes problematic left shoulder elevation even in a Lenke type 1 curve. Thirty-eight patients (3 male, 35 female, mean age 16.2 years, mean follow-up 24 mo) with Lenke type 1 curve underwent posterior corrective surgery using PSs. The upper instrumented vertebra was 1 level below the end vertebra in 14 patients (short, S group), and it was at the end vertebra in 24 patients (conventional, C group). There was no difference in the preoperative Cobb angle (51.8 vs. 58.0) or curve flexibility (49.7 vs. 46.1) between the 2 groups. Radiographic results, perioperative data, and scoliosis research society 22 scores were compared between the 2 groups. The postoperative Cobb angle of the main curve after surgery was 13.2±5.7 degrees in the S group and 10.6±7.3 degrees in the C group (not significant). The clavicle angle was -2.1±2.8 degrees versus -2.7±2.6 degrees before surgery (not significant), and 0.8±2.3 versus 3.8±2.4 after surgery (P<0.05). The number of fused vertebrae, mean surgical time, and estimated blood loss were significantly lower in the S group than in the C group. The scoliosis research society 22 score at follow-up was not different between the 2 groups. The short fusion strategy for a Lenke type 1 curve can produce equivalent correction of the main curve and clinical outcomes to conventional fusion strategy with less surgical time and blood loss, while maintaining better shoulder balance.

Experimental evaluations of the accuracy of 3D and 4D planning in robotic tracking stereotactic body radiotherapy for lung cancers

Due to the complexity of 4D target tracking radiotherapy, the accuracy of this treatment strategy should be experimentally validated against established standard 3D technique. This work compared the accuracy of 3D and 4D dose calculations in respiration tracking stereotactic body radiotherapy (SBRT). Using the 4D planning module of the CyberKnife treatment planning system, treatment plans for a moving target and a static off-target cord structure were created on different four-dimensional computed tomography (4D-CT) datasets of a thorax phantom moving in different ranges. The 4D planning system used B-splines deformable image registrations (DIR) to accumulate dose distributions calculated on different breathing geometries, each corresponding to a static 3D-CT image of the 4D-CT dataset, onto a reference image to compose a 4D dose distribution. For each motion, 4D optimization was performed to generate a 4D treatment plan of the moving target. For comparison with standard 3D planning, each 4D plan was copied to the reference end-exhale images and a standard 3D dose calculation was followed. Treatment plans of the off-target structure were first obtained by standard 3D optimization on the end-exhale images. Subsequently, they were applied to recalculate the 4D dose distributions using DIRs. All dose distributions that were initially obtained using the ray-tracing algorithm with equivalent path-length heterogeneity correction (3D EPL and 4D EPL) were recalculated by a Monte Carlo algorithm (3D MC and 4D MC) to further investigate the effects of dose calculation algorithms. The calculated 3D EPL, 3D MC, 4D EPL, and 4D MC dose distributions were compared to measurements by Gafchromic EBT2 films in the axial and coronal planes of the moving target object, and the coronal plane for the static off-target object based on the γ metric at 5%/3mm criteria (γ5%/3mm). Treatment plans were considered acceptable if the percentage of pixels passing γ5%/3mm (Pγ<1) ≥ 90%. The averaged Pγ<1 values of the 3D EPL, 3D MC, 4D EPL, and 4D MC dose calculation methods for the moving target plans are 95%, 95%, 94%, and 95% for reproducible motion, and 95%, 96%, 94%, and 93% for nonreproducible motion during actual treatment delivery. The overall measured target dose distributions are in better agreement with the 3DMC dose distributions than the 4DMC dose distributions. Conversely, measured dose distributions agree much better with the 4D EPL/MC than the 3D EPL/MC dose distributions in the static off-target structure, resulting in higher Pγ<1 values with 4D EPL/MC (91%) vs 3D EPL (24%) and 3D MC (25%). Systematic changes of target motion reduced the averaged Pγ<1 to 47% and 53% for 4D EPL and 4D MC dose calculations, and 22% for 3D EPL/MC dose calculations in the off-target films. In robotic tracking SBRT, 4D treatment planning was found to yield better prediction of the dose distributions in the off-target structure, but not necessarily in the moving target, compared to standard 3D treatment planning, for reproducible and nonreproducible target motion. It is important to ensure on a patient-by-patient basis that the cumulative uncertainty associated with the 4D-CT artifacts, deformable image registration, and motion variability is significantly smaller than the cumulative uncertainty occurred in standard 3D planning in order to make 4D planning a justified option.

Preformed vs Intraoperative Bending of Titanium Mesh for Orbital Reconstruction

The most accurate orbital reconstructions result from an anatomic repair of the premorbid orbital architecture. Many different techniques and materials have been used; unfortunately, there is currently no optimal method. This study compares the use of preformed vs intraoperative bending of titanium mesh for orbital reconstruction in 2-wall orbital fractures. Cadaver-based study. University hospital. Preinjury computed tomography scans were obtained in 15 cadaveric heads (30 orbits). Stereolithographic (STL) models were fabricated for 5 of the specimens (10 orbits). Two wall fractures (lamina papyracea and floor) were then generated in all orbits. Surgical reconstruction was performed in all orbits using 1 of 3 techniques (10 orbits each): (1) patient-specific implant molded from the preinjury STL model, (2) titanium mesh sheet bent freehand, and (3) preformed titanium mesh. Each technique was evaluated for orbital volume correction, contour accuracy, ease of use, and cost. No difference in volume restoration was found between the 3 techniques. Patient-specific implants had the greatest contour accuracy, poor ease of use, and highest cost. Freehand bending implants had the poorest contour accuracy, acceptable ease of use, and lowest cost. Preformed mesh implants had intermediate contour accuracy, excellent ease of use, and low cost. All 3 techniques provide equivalent orbital volume correction. However, preformed mesh implants have many advantages based on contour accuracy, ease of use, and relative cost.

Prevalence of ocular abnormalities in adults with Down syndrome in Hong Kong

Background/aimsThis was a cross-sectional survey to find the prevalence of visual impairment and eye diseases among adults with Down syndrome (DS) in Hong Kong.Methods91 DS patients over the age of...

Effect of blur and subsequent adaptation on visual acuity using letter and Landolt C charts: differences between emmetropes and myopes

To compare the effects of defocus induced blur and blur adaptation on visual acuity and to evaluate any differences between emmetropes and myopes using letter and Landolt C logMAR charts. The sample consisted of 26 volunteers, with a mean age of 27 ± 3 years, comprising 13 emmetropes (spherical equivalent range: -0.63 to +0.50 D) and 13 myopes (spherical equivalent range: -0.75 to -5.00 D). Monocular visual acuity (VA) was measured in each eye using letter and Landolt C logMAR charts under the following conditions: (1) with the distance refractive correction, (2) immediately after exposure to +2.00 D defocus and (3) following 60 min of binocular adaptation to +2.00 D blur. Objective refraction at the beginning and at the end of the experimental procedure was evaluated. Averaged VA data between the two eyes were used for analysis. Deterioration in VA with +2.00 D defocus was greater in the emmetropes compared to myopes for both charts. The mean difference between the two refractive groups was more pronounced for the Landolt-C (0.17 logMAR) compared to the letter chart (0.10 logMAR). The reduction in VA with blur was related to the amount of the refractive error. Following 60 min of adaptation, a significant improvement in VA was observed in both groups that did not differ between the two charts. The improvement in VA following adaptation using the letter chart was linearly correlated with spherical equivalent refractive correction. Myopes show higher tolerance to retinal defocus compared to emmetropes, which could be attributed to previous blur experience. The effect of blur on VA is more pronounced using Landolt C optotypes than with letters. Prolonged exposure to blur results in equally improved performance for both refractive groups.

Study of inhomogeneous tissue equivalent water thickness correction method in proton therapy

The inhomogeneous tissue equivalent water thickness correction method is an important part of research in proton radiotherapy. In this paper, we simulate the transport processes of a high-energy proton beam being injected into the water and other materials using Monte-Carlo multi-particle transport code Fluka, and according to the energy deposition distribution we obtain the depth of the Bragg peak when the protons are injected into different materials. Then we fit an analytic formula (R = αE0p) to the relationship between initial proton energy and the depth of the proton Bragg peak in different materials. It is found that for the different energies of proton beam being injected into non-uniform organization, the difference between the Bragg peak depth from fitting and the depth of the proton beam Bragg peaks from Fluka program is less than 1 mm. If we can establish a database about the relationship of Bragg peak ratio between medium and water, with electron density, then the equivalent water thickness correction method will be able to applied to the dose calculation of for homogeneous medium in proton therapy.

Laser in situ keratomileusis for high astigmatism in myopic and hyperopic eyes

To evaluate outcomes after laser in situ keratomileusis (LASIK) in highly astigmatic myopic and hyperopic eyes. University eye clinic. Retrospective case series. Eyes with more than 2.0 diopters (D) of astigmatism were identified from patient records. The mean preoperative cylinder was -3.92 D ± 0.82 (SD) in myopic eyes and -4.42 ± 1.10 D in hyperopic eyes. Patients were examined preoperatively and 3 months postoperatively. Laser in situ keratomileusis was performed with a Visumax femtosecond laser and a MEL-80 excimer laser. Preoperative and postoperative refractions were converted to polar values. Induced torsion and achieved correction of sphere and cylinder were determined. After 3 months, the mean sphere was 0.48 ± 0.68 D in myopic eyes and the mean cylinder -0.97 ± 0.52 D. Spherical equivalent (SE) correction was 0.05 ± 0.42 D from target. Astigmatism was 0.77 ± 0.62 D undercorrected (P<.01), and the mean induced torsion was -0.18 ± 0.51 D (P=.02). Astigmatic undercorrection was 21% of the intended correction. In hyperopia, the mean 3-month refraction was 0.79 ± 0.83 D in sphere and -1.38 ± 0.90 D in cylinder. The SE refraction was -0.01 ± 0.71 D from target. Astigmatism was 1.17 ± 0.81 D undercorrected (P<.01), with no significant torsion. Intended and achieved astigmatic corrections were correlated, with astigmatism being 28% undercorrected. Laser in situ keratomileusis in highly astigmatic eyes precisely corrected SE refraction but led to astigmatic undercorrection, particularly in hyperopia. Little to no torsion of the cylinder axis was induced.

Surgical hip dislocation versus hip arthroscopy for femoroacetabular impingement: clinical and morphological short-term results

Surgical hip dislocation (SHD) is an accepted standard to treat femoroacetabular impingement (FAI). However, arthroscopic techniques have gained widespread popularity and comparable results are reported. The purpose of this prospective comparative study was to test the hypothesis that, when compared to SHD, hip arthroscopy (HA) results in faster recovery, better short-term outcome, and equivalent morphological corrections. 38 patients presenting with clinically and morphologically verified isolated FAI were allocated to either HA or SHD. Morphological evaluation consisted of pre- and postoperative X-rays, and arthro-MRI. Demographic data, sport activities, hospital stay, complications, and the time off work were recorded. The subjective hip value, WOMAC, HHS, and hip abductor strength were measured up to 1 year. Shorter hospital stay and time off work, less pain at 3 months and 1 year, higher subjective hip values at 6 weeks and 3 months, and better WOMAC at 3 months were seen after HA. The HHS and the hip abductor strengths were higher in the HA group. However, morphological corrections at the head-neck-junction achieved by HA showed some overcorrection when compared to SHD. Labral refixation was performed less frequent in the HA group. When compared to SHD, HA results in faster recovery and better short-term outcome. However, some overcorrection of the cam deformity and limited frequency of labrum refixation with HA in this study may have a negative impact on long-term outcome.

Anterior corneal optical irregularity measured by higher‐order aberrations induced by a broad beam excimer laser

Background: The aim was to analyse anterior corneal optical irregularity in patients receiving photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with a conventional broad beam laser.Methods: Pre‐ and post‐operative anterior corneal aberrations including Zernike coefficients and root mean squares of higher‐order aberrations were measured and derived with a Placido‐ring‐based corneal topographer and wavefront software, respectively, from 768 right eyes of patients receiving either PRK or LASIK for myopia with a conventional broad beam excimer laser in National Taiwan University Hospital, Taipei, Taiwan. Multiple linear regression models selected by Mallows' Cp criteria were used to evaluate predictability of surgically induced aberrations and relevant factors.Results: Mean attempted spherical equivalent correction was ‐7.37 ± 2.33-D (range: ‐16.5 to ‐1.95). Root mean squares of higher‐order aberrations and variances of Zernike coefficients all increased significantly after surgery (p < 0.01). All post‐operative higher‐order aberrations increased with the amount of attempted myopic correction and secondary astigmatism increased with attempted cylindrical correction. LASIK surgery induced less coma and third‐order aberrations but more fifth‐ and sixth‐order aberrations than PRK, although squared partial correlation coefficients were low. Larger optic and transitional zones meant fewer higher‐order aberrations after surgery. Younger patients tended to have more surgically induced aberrations in the 3.0 mm pupil zone.Conclusions: Anterior corneal optical irregularity increased tremendously after refractive surgery by conventional broad beam lasers and correlated with greater attempted myopic correction, younger age and a smaller treatment zone. The effect of corneal flaps on post‐operative corneal irregularity differed trivially.