bluuebunny/crossref_metadata_2025 huggingface dataset:
Petrophysical Characterization and Fractal Analysis of Carbonate Reservoirs of the Eastern Margin of the Pre-Caspian Basin
Authors: Sha Feng , Xiao Lizhi , Mao Zhiqiang , Jia Chen
Published: December 2018

Petrophysical properties including pore structure and permeability are essential for successful evaluation and development of reservoirs. In this paper, we use casting thin section and mercury intrusion capillary pressure (MICP) data to investigate the pore structure characterization, permeability estimation, and fractal characteristics of Carboniferous carbonate reservoirs in the middle blocks of the eastern margin of the Pre-Caspian Basin. Rock casting thin sections show that intergranular and intragranular dissolution pores are the main storage spaces. The pore throats greater than 1 μm and lower than 0.1 μm account for 47.98% and 22.85% respectively. A permeability prediction model was proposed by incorporating the porosity, Swanson, and R35 parameters. The prediction result agrees well with the core sample data. Fractal dimensions based on MICP curves range from 2.29 to 2.77 with an average of 2.61. The maximum mercury intrusion saturation is weakly correlated with the fractal dimension, while the pore structure parameters such as displacement pressure and median radii have no correlation with fractal dimension, indicating that single fractal dimension could not capture the pore structure characteristics. Finally, combined with the pore types, MICP shape, and petrophysical parameters, the studied reservoirs were classified into four types. The productivity shows a good correlation with the reservoir types.
Assessing Submarine Slope Stability through Deterministic and Probabilistic Approaches: A Case Study on the West-Central Scotia Slope
Authors: MacKillop Kevin , Fenton Gordon , Mosher David , Latour Valerie , Mitchelmore Perry
Published: December 2018

A simplified geostatistical approach was adopted to assess the effect of spatial variability of soil properties on slope stability analysis in order to understand continental margin geologic processes and potential geohazards for an area of the central Scotian Slope, offshore Nova Scotia, Canada. The analyses are conducted on piston core samples, thus are restricted to ~12 m sub-seabed; however, the approach provides insight into the general effects of spatial and temporal variability. Data processing using geostatistics and assessment of spatial correlation are used to characterize the current dataset. A deterministic assessment was performed for both non-spatially averaged and spatially averaged core sections. The results indicate that the estimated factor of safety increased by about 30% when spatially averaged values were used. A probabilistic model is introduced to assess reliability of the slope. The approach makes use of estimates of both the mean and variance of input random variables (e.g., Su and γb). The model uses an exact probabilistic formulation for the total stress stability analysis and a Taylor series approximation for the effective stress stability analysis. In both cases, the mean and variance of the factor of safety are computed, leading to estimates of failure probability. The results suggest that the deterministic analysis is conservative with respect to slope reliability, although they do not lead to an estimate of the probability of failure. While these results indicate sediment instability is largely unlikely under static conditions, the reality is that many examples of submarine slope failure are observed in the geologic record. These results suggest that cyclic loading (earthquakes) or pre-conditioning factors (elevation of pore pressures) are critical for slope instability on the Scotian Slope.
A Cluster-Based Machine Learning Ensemble Approach for Geospatial Data: Estimation of Health Insurance Status in Missouri
Authors: Mueller Erik , Sandoval J. S. Onésimo , Mudigonda Srikanth , Elliott Michael
Published: December 2018

Mainstream machine learning approaches to predictive analytics consistently prove their ability to perform well using a variety of datasets, although the task of identifying an optimally-performing machine learning approach for any given dataset becomes much less intuitive. Methods such as ensemble and transformation modeling have been developed to improve upon individual base learners and datasets with large degrees of variance. Despite the increased generalizability and flexibility of ensemble approaches, the cost often involves sacrificing inference for predictive ability. This paper introduces an alternative approach to ensemble modeling, combining the predictive ability of an ensemble framework with localized model construction through the incorporation of cluster analysis as a pre-processing technique. The workflow not only outperforms independent base learners and comparative ensemble methods, but also preserves local inferential capability by manipulating cluster parameters and maintaining interpretable relative importance values and non-transformed coefficients for the overall consideration of variable importance. This paper demonstrates the ensemble technique on a dataset to estimate rates of health insurance coverage across the state of Missouri, where the cluster pre-processing assists in understanding both local and global variable importance and interactions when predicting high concentration areas of low health insurance coverage based on demographic, socioeconomic, and geospatial variables.
Hot Tearing of 9Cr3Co3W Heat-Resistant Steel during Solidification
Authors: Zhong Honggang , Li Xihao , Wang Biao , Wu Tieming , Zhang Yunhu , Liu Bin , Zhai Qijie
Published: December 2018

The linear contraction and hot tearing behavior of 9Cr3Co3W heat-resistant steel during solidification were studied by combining in-situ casting experiments and the corresponding numerical simulations. The linear contraction, stress and temperature of the samples were detected during solidification. The results show that the linear contraction of 9Cr3Co3W heat-resistant steel was 1.7% in the sand mold. Meanwhile, the critical temperature and stress of the hot tearing that occurred at the hot spot were 1304 °C and 0.72 MPa, respectively. The occurrence of hot tearing was observed at the tip of secondary dendrites along the primary dendritic arms, where the solute elements were significantly enriched at the final solidification.
Isolation and Characterization of Plant Growth-Promoting Endophytic Fungi from the Roots of Dendrobium moniliforme
Authors: Shah Sujit , Shrestha Roshani , Maharjan Sabitri , Selosse Marc-Andre , Pant Bijaya
Published: December 2018

The present study aims to identify the diverse endophytic fungi residing in the roots of Dendrobium moniliforme and their role in plant growth and development. Nine endophytic fungi were isolated from the root sections and characterized by molecular technique. Quantification of the indole acetic acid (IAA) compound by these endophytes was done. Further, Chemical profiling of R11 and R13 fungi was done by Gas Chromatography-Mass Spectroscopy (GC-MS). Asymbiotic seed derived protocorms of Rhynchostylis retusa was used for the plant growth assay to investigate the growth promoting activities of the fungal elicitor prepared from the isolated fungi from D. moniliforme. Among the isolated fungi, the relative dominant fungus was Fusarium sp. The R13 and R6 fungi were identified only at the genus level which concludes the fungi are of new species or strain. The indole acetic acid production was relatively higher in R10. Bioactive compound diversity was observed in the organic extract of R11 and R6. The presence of phenolic compound and essential oil suggest their contribution for the antimicrobial and antioxidant properties to their host plant, D. moniliforme. The plant growth assay result concluded, the fungal elicitor prepared from R10, Colletotrichum alatae was the best among all other for the plant growth activities.
Organogenesis at the Shoot Apical Meristem
Authors: Traas Jan
Published: December 2018

Lateral organ initiation at the shoot apical meristem involves complex changes in growth rates and directions, ultimately leading to the formation of leaves, stems and flowers. Extensive molecular analysis identifies auxin and downstream transcriptional regulation as major elements in this process. This molecular regulatory network must somehow interfere with the structural elements of the cell, in particular the cell wall, to induce specific morphogenetic events. The cell wall is composed of a network of rigid cellulose microfibrils embedded in a matrix composed of water, polysaccharides such as pectins and hemicelluloses, proteins, and ions. I will discuss here current views on how auxin dependent pathways modulate wall structure to set particular growth rates and growth directions. This involves complex feedbacks with both the cytoskeleton and the cell wall.
Teacher Questioning Practices over a Sequence of Consecutive Lessons: A Case Study of Two Mathematics Teachers
Authors: Dong Lianchun , Clarke David , Cao Yiming , Wang Lidong , Seah Wee Tiong
Published: December 2018

This study examined teacher questioning practices over a sequence of consecutive lessons in China. Based on the IRF (initiation–response–follow-up) framework, a comprehensive coding system was developed to analyze what kinds of verbal questions were initiated by the teachers to elicit mathematical information and in what ways the teachers made use of students’ verbal contributions. This study finds that all participating teachers’ questioning practices showed both variations and consistencies over the lesson sequence. It is argued that the act of asking questions in classroom interaction not only includes the teachers’ conscious planning so as to accomplish pedagogical goals, but also involves the teachers’ unconscious routine in how to build up on students’ thinking.
Public Transport-Based Crowdshipping for Sustainable City Logistics: Assessing Economic and Environmental Impacts
Authors: Gatta Valerio , Marcucci Edoardo , Nigro Marialisa , Patella Sergio Maria , Serafini Simone
Published: December 2018

This paper aims at understanding and evaluating the environmental and economic impacts of a crowdshipping platform in urban areas. The investigation refers to the city of Rome and considers an environmental-friendly crowdshipping based on the use of the mass transit network of the city, where customers/crowdshippers pick-up/drop-off goods in automated parcel lockers located either inside the transit stations or in their surroundings. Crowdshippers are passengers that would use the transit network anyhow for other activities (e.g., home-to-work), thus avoiding additional trips. The study requires firstly, estimating the willingness to buy a crowdshipping service like the one proposed here, in order to quantify the potential demand. The estimation is realized adopting an extensive stated preference survey and discrete choice modeling. Then, several scenarios with different features of the service are proposed and evaluated up to 2025 in terms of both externalities (local and global pollutant emissions, noise emissions and accidents reductions) and revenues. The results are useful to understand and quantify the potential of this strategy for last mile B2C deliveries. Moreover, it provides local policy-makers and freight companies with a good knowledge base for the future development of a platform for public transport-based crowdshipping and for estimating the likely impact the system could have both from an economic and environmental point of view.
Impact of Plasma Instability on Constraint of the Intergalactic Magnetic Field
Authors: Yan Dahai , Zhou Jianeng , Zhang Pengfei , Zhu Qianqian , Wang Jiancheng
Published: December 2018

A relativistic electron–positron pair beam can be produced in the interaction between TeV photons from a blazar and extragalactic background light. The relativistic e
± pairs lose energy through inverse-Compton scattering (ICS) photons of the cosmic microwave background or plasma instabilities. The dominant energy-loss process is under debate. Based on the assumption that the dominant energy-loss process is ICS, the resulting cascade GeV radiation is usually used to constrain the intergalactic magnetic field (IGMF). Here, we include the energy-loss due to plasma oblique instability in the calculation of cascade gamma-ray flux, and investigate the impact of the plasma instability on the constraint of IGMF. Up-to-date GeV data and archival TeV data of the blazar 1ES 0229+200 are used. The results indicate that even if the oblique instability cooling is dominating ICS cooling, the cascade flux could still be used to constrain the IGMF. It is found that with the ratio between the cooling rates of the oblique instability and the ICS varying from 0.1,1 to 10, the lower limit of the IGMF of the cascade flux and the gamma-ray data changes from 8 × 10−18 G, 5 × 10−18 G to 10−18 G. If the ratio between the two cooling rates is 30, the estimate of IGMF based on the cascade flux is invalid.
Emission Signatures from Sub-parsec Binary Supermassive Black Holes. II. Effect of Accretion Disk Wind on Broad Emission Lines
Authors: Nguyen Khai , Bogdanović Tamara , Runnoe Jessie C. , Eracleous Michael , Sigurdsson Steinn , Boroson Todd
Published: December 2018

We present an improved semi-analytic model for calculation of the broad optical emission-line signatures from sub-parsec supermassive black hole binaries (SBHBs) in circumbinary disks. The second-generation model improves on the treatment of radiative transfer by taking into account the effect of the radiation-driven accretion disk wind on the properties of the emission-line profiles. Analysis of 42.5 million modeled emission-line profiles shows that correlations between the profile properties and SBHB parameters identified in the first-generation model are preserved, indicating that their diagnostic power is not diminished. The profile shapes are a more sensitive measure of the binary orbital separation and the degree of alignment of the black hole mini-disks and are less sensitive to the SBHB mass ratio and orbital eccentricity. We also find that modeled profile shapes are more compatible with the observed sample of SBHB candidates than with our control sample of regular active galactic nuclei. Furthermore, if the observed sample of SBHBs is made up of genuine binaries, it must include compact systems with comparable masses and misaligned mini-disks. We note that the model described in this paper can be used to interpret the observed emission-line profiles once a sample of confirmed SBHBs is available but cannot be used to prove that the observed SBHB candidates are true binaries.
Late-time Observations of the Type Ia Supernova SN 2014J with the Hubble Space Telescope Wide Field Camera 3
Authors: Graur Or
Published: December 2018

Recent works have studied the late-time light curves of Type Ia supernovae (SNe Ia) when these were older than 500 days past B-band maximum light. Of these, SN 2014J, which exploded in the nearby galaxy M82, was studied with the Advanced Camera for Surveys onboard the Hubble Space Telescope (HST) by Yang et al. Here, I report complementary photometry of SN 2014J taken with the HST Wide Field Camera 3 when it was ∼360–1300 days old. My F555W measurements are consistent with the F606W measurements of Yang et al., but the F438W measurements are ∼1 mag fainter than their F475W measurements. I corroborate their finding that, even though SN 2014J has spatially resolved light echoes, its photometry is not contaminated by an unresolved echo. Finally, I compare the F438W and F555W light curves of SN 2014J to those of the other late-time SNe Ia observed to date and show that more intrinsically luminous SNe have slower light curve decline rates. This is consistent with the correlation claimed by Graur et al., which was based on a comparison of pseudo-bolometric light curves. By conducting a direct comparison of the late-time light curves in the same filters, I remove any systematic uncertainties introduced by the assumptions that go into constructing the pseudo-bolometric light curves, thus strengthening the Graur et al. claim.
Retinal Straylight and Complaint Scores 18 Months After Implantation of the AcrySof Monofocal and ReSTOR Diffractive Intraocular Lenses
Authors: Hofmann Thomas , Zuberbuhler Bruno , Cervino Alejandro , Montés-Micó Robert , Haefliger Eduard
Published: December 2018

Purpose:

To evaluate retinal straylight and patient complaint scores 18 months after implantation with the AcrySof ReSTOR diffractive multifocal intraocular lens (IOL) (Alcon Laboratories Inc).

Methods:

Retinal straylight was measured with the C-Quant (Oculus Optikgeräte GmbH) system in 40 eyes implanted with the AcrySof ReSTOR IOL (SA60D3) and in 40 eyes implanted with the AcrySof SA60AT monofocal IOL. Complaint scores were assessed by a questionnaire in both groups of patients at three different lighting conditions—day light, dimmed light, and at night.

Results:

Seventy-five percent of eyes (30/40) of the ReSTOR group and 80% of eyes (32/40) of the SA60AT control group showed a retinal straylight value within or better than the normal range. No statistically significant differences between groups were found (
P
=.790). Patients of the ReSTOR group showed significantly more complaint scores at all assessed lighting conditions: increasing factors were 1.53, 2.02, and 2.66, for day light, dimmed light, and night, respectively (
P
<.0001). Comparing the amount of straylight, the multifocal group had 20% more straylight, albeit not significant at the 1% level.

Conclusions:

The AcrySof ReSTOR IOL showed similar retinal straylight values compared to the monofocal IOL. Subjectively, patients with the diffractive IOL claimed significantly more glare for all light conditions, especially at night. [
J Refract Surg.
2009;25:485–492.]
Combined Corneal Topography and Corneal Wavefront Data in the Treatment of Corneal Irregularity and Refractive Error in LASIK or PRK Using the Carl Zeiss Meditec MEL 80 and CRS-Master
Authors: Reinstein Dan Z. , Archer Timothy J. , Gobbe Marine
Published: December 2018

Purpose:

To assess the efficacy, safety, and accuracy of TOSCA II (Topography Supported Custom Ablation) treatments for the correction of high corneal aberrations and refractive error following previous ocular surgery.

Methods:

Forty-eight eyes of 32 patients were included for study. Indications for TOSCA II treatment included small optical zone, decentered ablation, subjective visually significant higher order aberrations, and irregularly irregular astigmatism induced by LASIK, photorefractive keratectomy, radial keratotomy, conductive keratoplasty, cataract surgery, and deep lamellar keratoplasty. An ablation profile based on corneal topography data and corneal wavefront and manifest refraction was created using the CRS-Master software (Carl Zeiss Meditec) to treat corneal irregularity and refractive error simultaneously. Postoperative assessments were performed at 1 week and 1, 2, 3, 6, and 12 months.

Results:

Mean attempted spherical equivalent refraction (SE) was −1.12 A 1.97 diopters (D) (range: +1.13 to −10.50 D). Mean attempted cylinder correction was 1.34±1.65 D (range: 0.00 to 7.75 D). Median age was 38 years (range: 19 to 68 years). Median follow-up was 9.4 months. Accuracy: mean deviation from the intended SE correction was −0.19±0.94 D, 60% of eyes were within ±0.50 D and 77% of eyes were within ±1.00 D of the intended SE. Cylinder: the correction ratio was 1.49±0.85 and the error ratio was 0.87±0.69. Efficacy: 56% of eyes achieved uncorrected visual acuity of 20/20 or better and 88% achieved 20/40 or better. Safety: 34% of eyes gained one or more lines of best spectacle-corrected visual acuity, 15% lost one line, and no eye lost two or more lines. Contrast sensitivity: for the subset of eyes with below normal contrast sensitivity preoperatively, there was a statistically significant improvement in contrast sensitivity at 3 cycles per degree (cpd), 6 cpd, and 12 cpd (
P
<.05). Stability: the average change in refraction between 3 months and 1 year was +0.38±0.30 D. Higher order aberrations: the average higher order root-meansquare decreased by 21% and the average spherical aberration decreased by 41%.

Conclusions:

The MEL 80 CRS-Master TOSCA II software appears to be an effective treatment for decentrations, optical zone enlargement, and reduction of higher order aberrations. The refractive outcome was satisfactory after one treatment. [
J Refract Surg
. 2009;25:503–515.]
Presbyopia Treatment by Monocular Peripheral PresbyLASIK
Authors: Epstein Robert Leonard , Gurgos Mark Andrew
Published: December 2018

Purpose:

To investigate monocular peripheral presby-LASIK on the non-dominant eye with distance-directed monofocal refractive surgery on the dominant eye in treating presbyopia.

Methods:

One hundred three patients underwent treatment with a VISX S4 system and follow-up from 1.1 to 3.9 years (mean 27.4 months). Average patient age was 53.3 years. Preoperative refraction ranged from −9.75 to +2.75 diopters (D). Non-dominant eyes underwent peripheral presbyLASIK—an aspheric, pupil–size dependent LASIK to induce central corneal relative flattening and peripheral corneal relative steepening. Dominant eyes underwent monofocal refraction-based LASIK (75.8%), wavefront-guided LASIK, limbal relaxing incisions, or no treatment to optimize distance vision.

Results:

At final follow-up, 91.3% (94/103) of all patients, 89% (25/28) of hyperopes, and 92% (69/75) of myopes reported complete spectacle independence and 7.8% (8/103) used spectacles for less than 1 hour per week. Distance unaided visual acuity was at least 20/20 in 67.9% (19/28) of hyperopes and 70.7% (53/75) of myopes, at least 20/20 at 80 cm in 85.7% (24/28) of hyperopes and 84% (63/75) of myopes, and at least 20/20 at 40 cm in 71.4% (20/28) of hyperopes and 65.3% (49/75) of myopes. PresbyLASIK increased overall higher order aberrations similarly to refraction-based LASIK for myopes but to a greater extent in hyperopic cases. PresbyLASIK WaveScan spherical equivalent refraction was stable in myopes but migrated an average +0.31 D in hyperopes over the follow-up period.

Conclusions:

Monocular peripheral presbyLASIK is a valuable option for presbyopic patients considering refractive surgery. [
J Refract Surg
. 2009;25:516–523.]
Wavefront-guided LASIK for Myopia: Effect on Visual Acuity, Contrast Sensitivity, and Higher Order Aberrations
Authors: Keir Nancy J. , Simpson Trefford , Jones Lyndon W. , Fonn Desmond
Published: December 2018

Purpose:

To determine the impact of wavefront-guided LASIK for myopia with or without astigmatism on high and low contrast best spectacle-corrected visual acuity (BSCVA), photopic and mesopic contrast sensitivity, and higher order aberrations.

Methods:

Bilateral wavefront-guided LASIK (LADARVision4000; Hansatome microkeratome) was performed on 324 eyes (162 patients) with a mean spherical manifest refraction of −2.84±1.35 diopters (D) (range: −0.25 to −6.50 D) and astigmatism of −0.81±0.74 D (range: 0 to −4.00 D). Mean age was 37.7±9.3 years (range: 20 to 60 years). Best spectacle-corrected visual acuity and contrast sensitivity were assessed using ETDRS charts and vertical sinusoidal gratings, respectively. Higher order aberrations were measured using a Shack-Hartmann wavefront sensor, analyzed across a 5-mm pupil. Repeated measures and post hoc analyses determined statistical significance (
P
<.0025). Only right eyes were analyzed.

Results:

One hundred thirty-six eyes (84%) had uncorrected visual acuity of 20/20 or better 6 months postoperative; 80.9% (131 eyes) were within ±0.50 D of attempted correction. Statistically significant postoperative improvements were noted in high and low contrast BSCVA (both
P
⩽.001); in photopic contrast sensitivity at 3, 6, and 12 cycles per degree (cpd); and in mesopic contrast sensitivity at 12 and 18 cpd (all
P
⩽.001). With respect to higher order aberrations, a statistically significant change was seen in Zernike coefficients

Z

3

−
1

,

Z

3
1

,

Z

3

−
3

,

Z

3
3

, and

Z

4
4

following surgery (range of mean absolute change: 0.042 to 0.142 µm; all
P
⩽.001). All increased in magnitude except for

Z

3

−
3

, which decreased.

Conclusions:

Despite an increase in higher order aberrations, wavefront-guided LASIK yields excellent visual acuity and contrast sensitivity. Spherical aberration, which increases the most following non-wavefront-guided LASIK, showed no significant change. [
J Refract Surg.
2009;25:524–533.]
Agreement Between Pentacam and Videokeratography in Corneal Power Assessment
Authors: Savini Giacomo , Barboni Piero , Carbonelli Michele , Hoffer Kenneth J.
Published: December 2018

Purpose:

To investigate agreement between a rotating Scheimpflug camera (Pentacam, Oculus Optikgeräte GmbH) and two corneal topographers (TMS-2 Topography System, Tomey; and Keratron Scout, Optikon 2000 SpA) in measuring the corneal power of normal eyes.

Methods:

The mean corneal powers calculated by simulated keratometry (SimK) with each topographer were compared to those provided by the Pentacam in 71 patients. Specifically, the corneal power values of the Pentacam included in this analysis were the SimK (calculated using the measured anterior corneal radius and standard keratometric index of 1.3375) and the True net power (calculated using the anterior and posterior corneal curvatures and Gaussian optics formula for thick lenses, where the actual refractive index of the air, cornea, and aqueous humor are entered). Bland-Altman plots were used to investigate agreement and analysis of variance (ANOVA) was performed to detect statistical differences.

Results:

Although ANOVA did not disclose a statistically significant difference among the mean SimK values (TMS-2: 43.20±1.51 diopters [D], Keratron Scout: 43.29±1.48 D, Pentacam: 43.25±1.53 D), the 95% limits of agreement between the TMS-2 and Pentacam and between the Keratron Scout and Pentacam were wide (−1.05 to +0.94 D and −0.95 to +1.02 D, respectively). Agreement was even poorer when considering the mean True net power (42.00±1.54 D), which was significantly lower than the mean Pentacam SimK (
P
<.001).

Conclusions:

Although corneal topography and the Pentacam provide similar SimK values, their data should not be used interchangeably as only moderate agreement exists between them. Corneal power values calculated by the True net power are significantly lower than any SimK and cannot be entered into intraocular lens power formulas. [
J Refract Surg
. 2009;25:534–538.]
Repeatability and Reproducibility of Corneal Curvature Measurements Using the Pentacam and Keratron Topography Systems
Authors: Kawamorita Takushi , Nakayama Nanami , Uozato Hiroshi
Published: December 2018

Purpose:

To compare the repeatability and reproducibility of corneal curvature measurements using the Pentacam eye scanner (Oculus Optikgeräte GmbH) and Keratron corneal topographer (Optikon 2000 SpA).

Methods:

Axial topography maps were used to acquire measurements. Twenty-six eyes of 26 healthy patients were measured to determine repeatability and reproducibility. Another 10 eyes of 10 healthy patients were included in a parallel study. Three measurements per eye were performed. Repeatability was assessed via the coefficient of variation. Reproducibility was assessed using Bland-Altman plots. Linear correlations were used to determine the agreement between devices. A
P
value <.05 was considered statistically significant.

Results:

The majority of coefficient of variations for both devices were within 1%. The coefficient of variation of the Pentacam was higher in the superior cornea (
P
<.01). The mean difference (95% limits of agreement) in the flattest meridian between examiners was −0.03±0.27 diopters (D) (range: −0.56 to +0.49 D) for the Pentacam and −0.08±0.21 D (range: −0.50 to +0.33 D) for the Keratron. The mean difference (95% limits of agreement) in the steepest meridian was −0.10±0.26 D (range: −0.60 to +0.41 D) for the Pentacam and −0.11±0.22 D (range: −0.53 to +0.31 D) for the Keratron. The mean axial power for the central 3.0 mm of the Pentacam was statistically significantly lower than that of the Keratron (
P
<.01).

Conclusions:

Although statistically significant differences were noted, both devices provided repeatable and reproducible corneal measurements centrally. Pentacam repeatability outcomes indicate that superior corneal measurements should be interpreted with caution. [
J Refract Surg.
2009;25:539–544.]
A 14-year Follow-up of Photorefractive Keratectomy
Authors: Bricola Graziano , Scotto Riccardo , Mete Maurizio , Cerruti Simonetta , Traverso Carlo E.
Published: December 2018

Purpose:

To evaluate the long-term outcome of myopic photorefractive keratectomy (PRK).

Methods:

This prospective study included 31 patients (49 eyes) who underwent PRK between 1991 and 1993. A Summit UV200 excimer laser was used. Patients were divided into two groups—low myopia: preoperative <6.00 diopters (D) (range: −1.50 to −5.75 D) (n=19); and high myopia: preoperative ⩾6.00 D (range: −6.00 to −13.00 D) (n=12). Long-term postoperative follow-up was every 2 years up to 14 years. Refraction, visual acuity, corneal status, and intraocular pressure (IOP) were evaluated. At 14 years, corneal topography and endothelial cell count were performed.

Results:

At last follow-up, manifest refraction spherical equivalent (MRSE) for the low myopia group was −0.17±0.8, uncorrected visual acuity (UCVA) logMAR was −0.06±0.55, and best spectacle-corrected visual acuity (BSCVA) logMAR was 0.00±1.00. The high myopia group had a final MRSE of −0.67±1.4, UCVA log-MAR −0.11±0.55, and BSCVA logMAR −0.03±1.00. At 14 years, BSCVA for most eyes was at least equal to preoperative BSCVA. In both groups, haze increased between 3 and 6 months, then declined in the first year. A temporary increase of IOP was seen in 4 eyes. Complications were minor haze (2 eyes), transient anisocoria (9 eyes), and intraepithelial hemosiderin deposits (4 eyes). No abnormalities in endothelial cell count or morphology, astigmatism, or ectasia were noted. Three patients reported night vision disturbance, but the majority of patients were satisfied with the outcome based on subjective questionnaire (low myopia group: 84%; high myopia group: 75%).

Conclusions:

Our study demonstrates the safety of myopic PRK. [
J Refract Surg.
2009;25:545–552.]
Correlation of Aberrometry, Contrast Sensitivity, and Subjective Symptoms With Quality of Vision After LASIK
Authors: Bühren Jens , Martin Tim , Kühne Anja , Kohnen Thomas
Published: December 2018

Purpose:

To compare which parameter category (wavefront data, psychophysical data, or subjective symptoms) predicts best subjective quality of vision after LASIK.

Methods:

Twenty-eight eyes (15 patients) were included. Twenty-three eyes (12 patients) underwent uneventful LASIK; 5 eyes (3 patients) were symptomatic eyes treated with myopic LASIK elsewhere. Mean preoperative spherical equivalent refraction was −4.79±1.92 diopters (D) (range: −1.63 to −7.13 D); mean patient age was 36.6±7.4 years (range: 18 to 48 years). All examinations were performed 1 month postoperatively. The wavefront error was described with Zernike polynomials (6-mm pupil). Psychophysical tests included high-contrast visual acuity and contrast sensitivity with and without glare at 167 cd/m
−2
, 1.67 cd/m
−2
, and 0.167 cd/m
−2
with best spectacle correction. Correspondingly, overall subjective quality of vision and frequency of visual symptoms (glare, halos, starbursts, ghosting, blur) were assessed for three lighting conditions (photopic, high-mesopic, and low-mesopic) using a questionnaire with a visual analog scale. For each parameter category and each lighting condition, a multiple stepwise backwards regression model with the overall quality of vision item value as dependent was applied.

Results:

Under all lighting conditions, subjective symptom scores predicted subjective quality of vision best (adjusted R
2
=0.83–0.92) with blur as the main predictor throughout all conditions. Psychophysical tests did not significantly predict postoperative subjective quality of vision. The adjusted R
2
for the Zernike coefficients was highest for low-mesopic (0.56) and lowest for photopic conditions (0.31).

Conclusions:

Different parameter categories for the description of optical quality did not predict subjective quality of vision after LASIK equally. Subjective symptom scores had the highest predictability, whereas psychophysical tests with spectacle correction had no predictability. The latter probably do not reflect all dimensions of subjective quality of vision.

[
J Refract Surg
. 2009;25:559–568.]
Stability of LASIK in Topographically Suspect Keratoconus Confirmed Non-keratoconic by Artemis VHF Digital Ultrasound Epithelial Thickness Mapping: 1-year Follow-up
Authors: Reinstein Dan Z. , Archer Timothy J. , Gobbe Marine
Published: December 2018

Purpose:

To determine the 1-year stability of LASIK in corneas with topographic suspect keratoconus confirmed as non-keratoconic by epithelial thickness mapping.

Methods:

This was a retrospective case/control comparative study. Eyes suspected of keratoconus using criteria based mainly on Atlas (Carl Zeiss Meditec AG) and Orbscan II (Bausch & Lomb) topography were scanned by Artemis very high-frequency digital ultrasound (ArcScan Inc). Keratoconus was confirmed if the epithelial thickness profile showed relative epithelial thinning coincident with an eccentric posterior elevation best-fit sphere apex. Laser in situ keratomileusis was performed in all eyes where keratoconus was excluded by finding relatively thicker epithelium or not finding localized thinning over the topographically suspected cone. Patients were followed for 1 year after LASIK. A control group was generated matched within 0.50 diopter (D) for sphere, cylinder, and spherical equivalent refraction (SEQ) to compare refractive stability.

Results:

The average change in SEQ between 3 and 12 months was −0.10±0.30 D for the suspect keratoconus group and −0.10±0.28 D for controls. No statistically significant difference in shift from 3 months to 12 months in SEQ or cylinder between groups was noted. No statistically significant change in best spectacle-corrected visual acuity between groups was noted, with no eye losing 2 lines and 5% in the suspect keratoconus group and 2% of controls losing 1 line. No cases of ectasia were observed in either group.

Conclusions:

Suspect keratoconus, confirmed to be non-keratoconic by epithelial thickness profile criteria demonstrated equal stability to control eyes 1 year after LASIK. Epithelial thickness profiles may enable LASIK to be performed in eyes that would otherwise have been excluded due to topographic suspect keratoconus. Further follow-up is being carried out. [
J Refract Surg.
2009;25:569–577.]
Objective Evaluation of the Visual Benefit in Contact Lens Fitting After Complicated LASIK
Authors: Villa-Collar César , González-Méijome José Manuel , Gutiérrez-Ortega Ramón
Published: December 2018

Purpose:

To report the clinical application of the measurement of luminous distortion under scotopic conditions and wavefront aberrations to objectively corroborate the optical and visual benefit of contact lens fitting to rehabilitate vision after complicated LASIK.

Methods:

Seven eyes (four patients) that underwent LASIK for the correction of myopia with different postoperative visual complaints are reported in this observational case series. Luminous distortion index with the Starlights System v1.0 (Novosalud) and total wavefront aberration using a Hartmann-Shack aberrometer were used to objectively quantify the benefit of contact lens fitting to corroborate subjective improvements in terms of patient satisfaction and photopic visual acuity. Uncorrected visual acuity, best spectacle and contact lens corrected visual acuity, root-mean-square for higher order aberrations, and luminous distortion under scotopic conditions were obtained.

Results:

Visual complaints were attributed to a small optical zone, decentered ablation, and iatrogenic ectasia, and patients were fit with contact lenses of different materials, designs, and fitting approaches. Reverse geometry rigid gas permeable contact lenses are beneficial in reducing higher order aberrations to less than one half of the cornea and total aberrometry, with a positive effect in reducing luminous distortion up to 100% associated with complaints of night vision distortion to less than 5% in patients with small optical zones or decentered ablations. Artificial pupil cosmetic soft contact lens also decreased the luminous distortion index.

Conclusions:

The visual benefit reported by patients after contact lens fitting in postoperative complications secondary to LASIK can be objectively measured through the luminous distortion under scotopic conditions. [
J Refract Surg
. 2009;25:591–598.]
Clinical Results of a Corneal Radius Correcting Factor in Calculating Intraocular Lens Power After Corneal Refractive Surgery
Authors: Rosa Nicola , Capasso Luigi , Lanza Michele , Borrelli Maria
Published: December 2018

Purpose:

To describe the clinical results of a corneal radius correcting factor (CRCF), which is based on the axial length and independent of knowledge from the previous surgical procedure, in calculating intraocular lens (IOL) power in eyes that developed cataract after corneal refractive surgery.

Methods:

Intraocular lens power for 62 eyes that previously underwent corneal refractive surgery was calculated with the SRK/T and SRK II formulas using an axial length–related CRCF, and the expected refractive errors were compared with the actual postoperative refractive errors.

Results:

Using the CRCF, the refractive outcomes ranged between −3.25 and +1.00 diopters (D) (mean −0.41±0.75 D), with 37 (60%) eyes within ±0.50 D and 53 (85%) eyes within ±1.00 D of the intended refraction. Using the raw data, without the correcting factor, the refractive outcomes would have ranged between −2.00 and +5.00 D (mean +2.17±1.45 D) with 7 (11%) eyes within ±0.50 D and 15 (24%) eyes within ±1.00 D of the intended refraction.

Conclusions:

Pending further validation through a larger prospective evaluation, the CRCF combined with the SRK/T formula is recommended in eyes with an axial length up to 30 mm and the average IOL power calculated with the SRK/T and SRK II formulas when the axial length is >30 mm. [
J Refract Surg
. 2009;25:599–603.]
Late-onset Severe Diffuse Lamellar Keratitis Associated With Uveitis After LASIK in a Patient With Ankylosing Spondylitis
Authors: Díaz-Valle David , Arriola-Villalobos Pedro , Benitez-del-Castillo Sánchez José M. , Bueso Enrique Santos , Martínez de la Casa José M. , Sardiña Ricardo Cuiña
Published: December 2018

Purpose:

To report a case of diffuse lamellar keratitis (DLK) associated with acute anterior uveitis that occurred 3 years after uneventful LASIK in a patient with a history of ankylosing spondylitis and recurrent acute anterior uveitis.

Methods:

A 36-year-old man presented with pain and decreased vision in the left eye. Left eye visual acuity was 20/100. He had undergone bilateral LASIK 3 years prior to presentation to treat moderate myopia.

Results:

Slit-lamp examination revealed aqueous flare and cells, vertical corneal folds, and cell aggregates at the central interface. Flattening and thinning of the cornea were observed with Pentacam (Oculus Optikgeräte GmbH). Diffuse lamellar keratitis stage III was diagnosed and intensive corticosteroid and anticollagenolytic treatment was started with satisfactory results.

Conclusions:

Acute anterior uveitis may be a predisposing factor for late-onset DLK after LASIK surgery. Indication of LASIK in patients at high risk of developing recurrent flares of acute anterior uveitis, such as those with spondyloarthropathies, should be carefully considered. [
J Refract Surg
. 2009;25:623–625.]
Bilateral Complicated Stromal Dissections During Mechanical Epikeratome Separation of the Corneal Epithelium
Authors: Chen Yan-Ming , Hu Fung-Rong , Su Pei-Yuang , Chen Wei-Li
Published: December 2018

Purpose:

To present a case of bilateral inadvertent stromal cuts during mechanical epikeratome separation of the corneal epithelium using a Centurion SES epikeratome (Norwood EyeCare Pty Ltd).

Methods:

A 25-year-old woman underwent epi-LASIK surgery. Preoperative examinations showed no remarkable findings. After epithelial flap creation, a linear stromal cut near the temporal upper flap edge was found in the right eye. An irregular stromal cut involving the central cornea was found in the left eye after undergoing epi-LASIK with a new separator. Excimer laser ablation was continued in both eyes without flap reposition.

Results:

Six months postoperatively, best spectacle-corrected visual acuity was 20/20 in the right eye and 20/25 in the left eye. Corneal topographic examination revealed a regular pattern in the right eye and irregularities in the left.

Conclusions:

Stromal dissection during mechanical separation of the corneal epithelium with a Centurion SES epikeratome is a potential complication of epi-LASIK. Visual impairment can result from such complications. [
J Refract Surg.
2009;25:626–628.]
One-month Outcomes of Wavefront-guided LASIK for Low to Moderate Myopia With the VISX STAR S4 Laser in 32,569 Eyes
Authors: Schallhorn Steven C. , Venter Jan A.
Published: December 2018

Purpose:

To determine the safety and efficacy of wavefront-guided LASIK for the correction of low to moderate myopia, as performed by surgeons employed by Optical Express, a large corporate provider.

Methods:

Data were extracted from the Optical Express central database on 22,900 patients (42,143 eyes) who underwent primary LASIK to treat low to moderate myopia and/or astigmatism. All treatments used a wavefront-guided ablation profile and had a refractive target of emmetropia. Outcomes were evaluated using 1-month follow-up data, which were available for 32,569 eyes of 17,713 patients (77% follow-up). Complications were tabulated using all available data.

Results:

The mean manifest spherical equivalent (MSE) was reduced from −2.97±1.33 diopters (D) (range: −0.37 to −6.00 D) to −0.03±0.29 D (range: −3.50 to −4.50 D) 1 month after surgery. Ninety-four percent of eyes were within 0.50 D of the intended correction, and the correlation coefficient of the attempted versus achieved MSE was 0.96. Uncorrected visual acuity (UCVA) of 20/20 or better was achieved in 92% of eyes; 99% of eyes achieved UCVA of 20/40 or better. Among patients who had bilateral laser vision correction, 98% achieved 20/20 uncorrected binocular vision. Average best spectacle-corrected visual acuity (BSCVA) improved slightly 1 month after surgery (mean change: +0.01 logMAR). There were 210 (0.67%) eyes that lost 2 or more lines of BSCVA; however, all eyes were 20/40 or better. Intraoperative complications occurred in 25 eyes (0.06%; 1:1686), and postoperative complications occurred in 210 eyes (0.64%; 1:155). The most common complications were dry eye (n=58; 0.18%; 1:562) and mild diffuse lamellar keratitis (grade 1 or 2) (n=58; 0.18%; 1:562).

Conclusions:

Wavefront-guided LASIK can safely and effectively correct low to moderate myopia, as demonstrated by 1-month postoperative visual outcomes from a large number of patients. [
J Refract Surg
. 2009;25: S634–S641.]
Satisfaction of 13,655 Patients With Laser Vision Correction at 1 Month After Surgery
Authors: Brown Mitchell C. , Schallhorn Steven C. , Hettinger Keith A. , Malady Stephanie E.
Published: December 2018

Purpose:

To assess the level of laser vision correction patient satisfaction achieved by a large corporate provider of refractive surgery.

Methods:

A computer-based, interactive survey was used to query patients regarding their satisfaction with the services, experience, and results of their laser vision correction procedure.

Results:

Responses from 13,655 consecutive patients who completed their 1-month postoperative examination were analyzed in this study. A very high level of satisfaction was observed both for the quality of postoperative care provided (98.6%) and for the visual results obtained (95.0%). Most patients (94.2%) indicated that the surgery improved their life, and most would recommend both laser vision correction (96.5%) and the corporate provider (97.5%) to friends and family.

Conclusions:

Patients report a high level of satisfaction with laser vision correction performed by a large corporate provider. [
J Refract Surg
. 2009;25:S642–S646.]
Using an International Medical Advisory Board to Guide Clinical Governance in a Corporate Refractive Surgery Model
Authors: Vukich John A.
Published: December 2018

Purpose:

To describe the role played by the International Medical Advisory Board (IMAB) in clinical and corporate governance at Optical Express, a corporate provider of refractive surgery.

Methods:

A review of goals, objectives, and actions of the IMAB.

Results:

The IMAB has contributed to study design, data analysis, and selection of instruments and procedures. Through interactions with Optical Express corporate and clinical staff, the IMAB has supported management's effort to craft a corporate culture focused on continuous improvement in the safety and visual outcomes of refractive surgery.

Conclusions:

The IMAB has fashioned significant changes in corporate policies and procedures and has had an impact on corporate culture at Optical Express.

[
J Refract Surg
. 2009;25:S647-S650.]
The Role of Biostatistics in the Quality Improvement of Refractive Surgery
Authors: Hettinger Keith A.
Published: December 2018

Purpose:

To demonstrate how the large quantity of uniformly collected data available to a corporate refractive surgery provider, Optical Express, is applied to drive improvements in patient outcomes.

Methods:

Optical Express employs a skilled team of biostatisticians to analyze the information in its electronic medical records database of over 5,500,000 patient records. The techniques used to ensure high data quality and the selection of statistical methods used in making data-driven clinical decisions are described. The importance of appropriate statistical methods is demonstrated in an example in which the effect of age on refractive outcomes in low myopes is studied. The use of a corporate database in prospective and retrospective analyses is detailed.

Results:

By providing the resources necessary to interpret the information in Optical Express' medical records database, the biostatistics department has helped Optical Express refine its procedures and improve surgical protocols and patient outcomes.

Conclusions:

Biostatistical analyses help transform the large quantities of uniformly collected clinical data available to a corporate surgery provider into information that can be applied to improve clinical practice. Such data-driven process improvements play a key role in improving patient outcomes. [
J Refract Surg
. 2009;25:S651–S654.]