Magnification Changes Research Articles

Estimation of pupil size at iris plane and its magnification after cataract surgery.

To estimate the pupil size (at the iris plane) under photopic (PPH) and scotopic (PS) conditions after phacoemulsification with intraocular lens (IOL) implantation. This retrospective observational cohort study included 190 virgin eyes from 190 patients who underwent cataract surgery with IOL implantation. Data collected with Aladdin (Topcon), AS-OCT MS-39 (CSO), and iTrace (Tracey) were SimK, mean pupillary power at 6 mm (MPP), anterior chamber depth (ACD), lens thickness (LT), axial length (AL), lens rise (LR), PPH and PS before and after surgery at 30 days, dysfunctional lens index, and opacity grade. The position of the postoperative iris plane (PIP) was measured manually with MS-39, and a multivariate regression formula was developed to predict it. Statistical analysis was performed using Statistical Package for Social Science (SPSS) (IBM). The mean and standard deviations were 42.61 ± 3.20 D for MMP at 6 mm, 3.35 ± 0.37 mm for ACD, 3.89 ± 0.18 mm for PIP (P < 0.01), 4.55 ± 0.42 mm for LT, 0.43 ± 0.24 mm for LR, and 25.91 ± 3.03 mm for AL. The mean preoperative and postoperative topographic pupil magnification was 12% and 14.22%, respectively (P < 0.01). Despite an increase in magnification, the postoperative pupil was smaller than the preoperative one both for scotopic and photopic conditions: The larger the preoperative pupil, the more it tends to reduce in the postoperative period. Analysis of the preoperative topographic pupil alone is not sufficient for a correct indication of the optical zone and total diameter of IOL to be implanted but must be correlated with biometric data. The topographic pupil, therefore, undergoes a change in magnification from the preoperative period to the postoperative period. Furthermore, the real pupil presents a modification and, in most cases, tends to be smaller postoperatively in both photopic and scotopic conditions.

Patient Re-Identification Based on Deep Metric Learning in Trunk Computed Tomography Images Acquired from Devices from Different Vendors

During radiologic interpretation, radiologists read patient identifiers from the metadata of medical images to recognize the patient being examined. However, it is challenging for radiologists to identify “incorrect” metadata and patient identification errors. We propose a method that uses a patient re-identification technique to link correct metadata to an image set of computed tomography images of a trunk with lost or wrongly assigned metadata. This method is based on a feature vector matching technique that uses a deep feature extractor to adapt to the cross-vendor domain contained in the scout computed tomography image dataset. To identify “incorrect” metadata, we calculated the highest similarity score between a follow-up image and a stored baseline image linked to the correct metadata. The re-identification performance tests whether the image with the highest similarity score belongs to the same patient, i.e., whether the metadata attached to the image are correct. The similarity scores between the follow-up and baseline images for the same “correct” patients were generally greater than those for “incorrect” patients. The proposed feature extractor was sufficiently robust to extract individual distinguishable features without additional training, even for unknown scout computed tomography images. Furthermore, the proposed augmentation technique further improved the re-identification performance of the subset for different vendors by incorporating changes in width magnification due to changes in patient table height during each examination. We believe that metadata checking using the proposed method would help detect the metadata with an “incorrect” patient identifier assigned due to unavoidable errors such as human error.

Estimation of pore structure and permeability in tight carbonate reservoir based on machine learning (ML) algorithm using SEM images of Jaisalmer sub-basin, India

Analyzing the pore structure in carbonate reservoirs plays a crucial role in predicting fluid flow characteristics within these formations. The goal of the study was to use machine learning techniques for pore structure analysis and estimation of permeability in carbonate reservoirs. We implemented these algorithms by examining 2D scanning electron microscope (SEM) images of carbonate samples from the Jaisalmer sub-basin captured at various magnifications. In the initial stage of the analysis, various binarization algorithms were applied to determine carbonate sample porosity. Among these algorithms, the MaxEntropy algorithm gave a porosity value closely aligned with those obtained through petrography analysis. We employed the watershed algorithm to find the pore network parameters of carbonate samples at various magnifications. We observed that changes in magnification affected pore network parameters, resulting in a reduction in pore size distribution, throat radius, and grain size. Subsequently, we employed the numerical lattice Boltzmann method (LBM) to estimate the permeability of carbonate samples and compared to values derived from well logs. We employed machine learning (ML) algorithms, specifically Artificial Neural Network (ANN) and Support Vector Machine (SVM), to predict the permeability of carbonate samples. The input features for these models were the pore network parameters, while the LBM permeability values served as the output. We examine the prediction performance of these methods against the measured LBM permeability by conducting the error analysis and the coefficient of determination (R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}^{2}$$\\end{document}) calculation. Our findings revealed that the ANN models outperformed the SVM models. Specifically, the ANN model displayed an impressive R2 value of 0.892, along with root mean square error (RMSE), mean squared error (MSE) and, mean absolute error (MAE) values of 1.927, 3.716 and 1.580, respectively. In contrast, the SVM model yielded an R2 value of 0.849, with RMSE, MSE and, MAE values of 2.324, 5.401 and, 2.166 respectively, when assessed on testing data of measured permeability. This study found that ANN is more dependable, robust, and precise than SVM in forecasting carbonate sample permeability.

A Monocular Variable Magnifications 3D Laparoscope System Using Double Liquid Lenses.

During minimal invasive surgery (MIS), the laparoscope only provides a single viewpoint to the surgeon, leaving a lack of 3D perception. Many works have been proposed to obtain depth and 3D reconstruction by designing a new optical structure or by depending on the camera pose and image sequences. Most of these works modify the structure of the conventional laparoscopes and cannot provide 3D reconstruction of different magnification views. In this study, we propose a laparoscopic system based on double liquid lenses, which provide doctors with variable magnification rates, near observation, and real-time monocular 3D reconstruction. Our system composes of an optical structure that can obtain auto magnification change and autofocus without any physically moving element, and a deep learning network based on the Depth from Defocus (DFD) method, trained to suit inconsistent camera intrinsic situations and estimate depth from images of different focal lengths. The optical structure is portable and can be mounted on conventional laparoscopes. The depth estimation network estimates depth in real-time from monocular images of different focal lengths and magnification rates. Experiments show that our system provides a 0.68-1.44x zoom rate and can estimate depth from different magnification rates at 6fps. Monocular 3D reconstruction reaches at least 6mm accuracy. The system also provides a clear view even under 1mm close working distance. Ex-vivo experiments and implementation on clinical images prove that our system provides doctors with a magnified clear view of the lesion, as well as quick monocular depth perception during laparoscopy, which help surgeons get better detection and size diagnosis of the abdomen during laparoscope surgeries.

Monte-Carlo simulation for calculating phakic supplementary lenses based on a thick and thin lens model using anterior segment OCT data

BackgroundPhakic lenses (PIOLs, the most common and only disclosed type being the implantable collamer lens, ICL) are used in patients with large or excessive ametropia in cases where laser refractive surgery is contraindicated. The purpose of this study was to present a strategy based on anterior segment OCT data for calculating the refraction correction (REF) and the change in lateral magnification (ΔM) with ICL implantation.MethodsBased on a dataset (N = 3659) containing Casia 2 measurements, we developed a vergence-based calculation scheme to derive the REF and gain or loss in ΔM on implantation of a PIOL having power PIOLP. The calculation concept is based on either a thick or thin lens model for the cornea and the PIOL. In a Monte-Carlo simulation considering, all PIOL steps listed in the US patent 5,913,898, nonlinear regression models for REF and ΔM were defined for each PIOL datapoint.ResultsThe calculation shows that simplifying the PIOL to a thin lens could cause some inaccuracies in REF (up to ½ dpt) and ΔM for PIOLs with high positive power. The full range of listed ICL powers (− 17 to 17 dpt) could correct REF in a range from − 17 to 12 dpt with a change in ΔM from 17 to − 25%. The linear regression considering anterior segment biometric data and the PIOLP was not capable of properly characterizing REF and ΔM, whereas the nonlinear model with a quadratic term for the PIOLP showed a good performance for both REF and ΔM prediction.ConclusionWhere PIOL design data are available, the calculation concept should consider the PIOL as thick lens model. For daily use, a nonlinear regression model can properly predict REF and ΔM for the entire range of PIOL steps if a vergence calculation is unavailable.

A computer vision based optical method for measuring fluid level in cell culture plates.

For a transparent well with a known volume capacity, changes in fluid level result in predictable changes in magnification of an overhead light source. For a given well size and fluid, the relationship between volume and magnification can be calculated if the fluid's index of refraction is known or in a naive fashion with a calibration procedure. Light source magnification can be measured through a camera and processed using computer vision contour analysis with OpenCV. This principle was applied in the design of a 3D printable sensing device using a raspberry pi zero and a camera.

Effect of Low-Concentration Atropine Eye Drops in Controlling the Progression of Myopia in Children: A One- and Two-Year Follow-Up Study

ABSTRACT Purpose Atropine eye drops have been shown to slow the progression of myopia, but there has been limited research on the effectiveness of 0.05% atropine in treating myopia. This study aimed to investigate the safety and efficacy of 0.05% atropine eye drops in controlling myopia in children. Methods The study included 424 participants aged 6 to 12 years between January 1, 2015, and January 1, 2021. Of these, 213 were randomly assigned to the 0.05% atropine group and 211 to the placebo group. The cycloplegic spherical equivalent (SE), axial length (AL), corneal curvature (K), and anterior chamber depth (ACD) were measured using IOLMaster. The lens power and corneal astigmatism were also determined. The changes in ocular biometric parameters were compared between the two groups, and the contributions of ocular characteristics to SE progression were calculated and compared. Results Over a 12-month period, the changes in spherical equivalent were −0.03 ± 0.28 and −0.32 ± 0.14 in the atropine and placebo groups, respectively (P = .01). The changes in axial length were 0.06 ± 0.11 and 0.17 ± 0.12, respectively (P = .01). At 18 and 24 months, there were significant differences in axial length and spherical equivalent between the atropine and placebo groups. Multiple regression models accounting for changes in AL, K, and lens magnification explained 87.23% and 98.32% of SE changes in the atropine and placebo groups, respectively. At 1 year (p = .01) and 2 years (p = .03), there were significant differences in photophobia between the atropine and placebo groups. Conclusions This two-year follow-up study demonstrates that 0.05% atropine eye drops are safe and effective in preventing the development of myopia in school-aged children.

Magnification and Refocusing Comparison in Cataract Surgery Using a Heads-Up Three-Dimensional Visualization System versus Conventional Binocular Microscopy.

To comparemagnification and refocusing during phacoemulsification with the NGENUITY® 3-D Visualization System (3-D) versus the conventional microscope (CM) OPMI LUMERA 700. This study was performed in the Department of Anterior Segment of the Fundación Hospital Nuestra Señora de la Luz. Prospective, randomized, cross-sectional, multi-surgeon, and comparative study. This study enrolled 100 patients (eyes) scheduled for phacoemulsification to measure the number of times changes in focusing and magnification were needed during cataract surgery. Our study included 100 patients. From the endpoints evaluated, "zoom-in" showed statistically significant differences for all of the four predefined cataract surgery steps (means: Step 1, 0.38 (CM) vs 0.08 (3-D); Step 2, 0.36 (CM) vs 0.06 (3-D); Step 3, 0.54 (CM) vs 0.22 (3-D); Step 4, 0.56 (CM) vs 0.24 (3-D); all comparisons, p <0.05). In Step 4, there was a statistically significant increased use of "focus-out" for the 3-D system (mean 0.16 (CM) vs 0.58 (3-D); p <0.05). "Focus-in" and "zoom-out" showed no group differences for all steps. The duration of surgery with the 3-D system was longer at each step and overall. The percentage of light intensity did not show a statistically significant difference between both systems, with a mean of 99.45 for CM vs 98.43% for the heads-up system. The heads-up 3-D system is a safe option that offers excellent magnification for anterior segment visualization. The surgical time is longer, but adjusting settings like light intensity and brightness may facilitate some surgical steps early in the learning curve.

THREE-COMPONENT LENS ZOOM-AFOCAL TRANSFOCAL SYSTEMS FOR THREAD RANGEFINDER

Problems. Synthesis of zoom zooms, which use zoom-afocal systems together with fixed lenses. Creation of a method of parametric synthesis of a three-component zoom-afocal system of a zoom-zoom based on the requirements for the required range of change in angular magnification, permissible cutting of peripheral beams of rays, the field of view of the system and the external location of the aperture diaphragm.&#x0D; The aim of the study. Development of a method for the synthesis of a three-component zoom-afocal system suitable for computer automation.&#x0D; Methodology of implementation. The theory of optical systems composed of thin components is used. Based on this theory, a system of equations is created in which the distances between the components are unknown. To ensure manufacturability, the first and third components of the system are identical. Using the formulas for angles and heights of zero rays, taking into account the requirements for permissible vignetting of beams and the angles of the zoom field of view, the necessary light diameters of the components are calculated.&#x0D; Research results. The resulting formulas for the overall calculation of the zoom-afocal system allow you to take into account the requirements for the longitudinal and transverse dimensions of the system, the position of the aperture diaphragm, determine the focal lengths of the components and their relative location depending on the angular magnification over the entire range of its change. It is established that a three-component system with identical first and second components has a variable axial length, which is maximal at an angular increase of one.&#x0D; Conclusions. The created method of parametric synthesis of a three-component zoom-afocal system for a zoom-zoom, in which the aperture diaphragm of a fixed lens serves as the aperture diaphragm, allows you to automate the dimensional calculation of the system and determine the laws of linear movement of its components along the optical axis.

Intraoperative zoom lens calibration for high magnification surgical microscope

Background and objectivesAn augmented reality (AR)-based surgical guidance system is often used with high-magnification zoom lens systems such as a surgical microscope, particularly in neurology or otolaryngology. To superimpose the internal structures of relevant organs on the microscopy image, an accurate calibration process to obtain the camera intrinsic and hand–eye parameters of the microscope is essential. However, conventional calibration methods are unsuitable for surgical microscopes because of their narrow depth of focus at high magnifications. To realize AR-based surgical guidance with a high-magnification surgical microscope, we herein propose a new calibration method that is applicable to the highest magnification levels as well as low magnifications. MethodsThe key idea of the proposed method is to find the relationship between the focal length and the hand–eye parameters, which remains constant regardless of the magnification level. Based on this, even if the magnification changes arbitrarily during surgery, the intrinsic and hand–eye parameters are recalculated quickly and accurately with one or two pictures of the pattern. We also developed a dedicated calibration tool with a prism to take focused pattern images without interfering with the surgery. ResultsThe proposed calibration method ensured an AR error of < 1 mm for all magnification levels. In addition, the variation of focal length was within 1% regardless of the magnification level, and the corresponding variation with the conventional calibration method exceeded 20% at high magnification levels. ConclusionsThe comparative study showed that the proposed method has outstanding accuracy and reproducibility for a high-magnification surgical microscope. The proposed calibration method is applicable to various endoscope or microscope systems with zoom lens.

Monte-Carlo simulation of a thick lens IOL power calculation.

The purpose of this Monte-Carlo study is to investigate the effect of using a thick lens model instead of a thin lens model for the intraocular lens (IOL) on the resulting refraction at the spectacle plane and on the ocular magnification based on a large clinical data set. A pseudophakic model eye with a thin spectacle correction, a thick cornea (curvatures for both surfaces and central thickness) and a thick IOL (equivalent power PL derived from a thin lens IOL, Coddington factor CL (uniformly distributed from -1.0 to 1.0), either preset central thickness LT = 0.9 mm (A) or optic edge thickness ET = 0.2 mm, (B)) was set up. Calculations were performed on a clinical data set containing 21 108 biometric measurements of a cataractous population based on linear Gaussian optics to derive spectacle refraction and ocular magnification using the thin and thick lens IOL models. A prediction model (restricted to linear terms without interactions) was derived based on the relevant parameters identified with a stepwise linear regression approach to provide a simple method for estimating the change in spectacle refraction and ocular magnification where a thick lens IOL is used instead of a thin lens IOL. The change in spectacle refraction using a thick lens IOL with (A) or (B) instead of a thin lens IOL with identical power was within limits of around ±1.5 dpt when the thick lens IOL was placed with its haptic plane at the plane of the thin lens IOL. In contrast, the change in ocular magnification from considering the IOL as a thick lens instead of a thin lens was small and not clinically significant. This Monte-Carlo simulation shows the impact of using a thick lens model IOL with preset LT or ET on the resulting spherical equivalent refraction and ocular magnification. If IOL manufacturers would provide all relevant data on IOL design data and refractive index for all power steps, this would make it possible to perform direct calculations of refraction and ocular magnification.

Three-component lens zoom-afocal transfocal systems

Parametric synthesis of zoom-afocal optical systems for zooms. Development of an algorithm for overall calculation of three-component zoom-afocal systems taking into account their overall limitations, ensuring the required range of change in angular magnification and field of view of the zoom lens, admissible vignetting of extreme beams of rays when changing the field of view in the entire specified range. Synthesis of an afocal system for a fixed lens, the entrance pupil of which is behind the afocal system. Creation of a universal analytical and suitable for computer automation algorithm for calculating the optical and dimensional parameters of the components of zoom-afocal three-component zoom systems. The zoom-afocal system is represented by thin components. A system of equations is created in which the distances between the components are unknown. The values of these distances are determined from the equations, which provide the required values of the angular magnification and zero optical power of the afocal system. At the same time, the values of the optical powers of the components and their ratio should ensure positive values of the distances between them. Using the formulas for the angles and heights of zero rays on the components of the system and taking into account the permissible vignetting of the beam from the edge of the field of view, the required light diameters of the components are determined. The obtained analytical dependencies make it possible to determine the focal distances of its components and their relative location over the entire range of the desired change in angular magnification based on the initial data on the admissible longitudinal and transverse dimensions of the afocal system. It was established that the afocal system has a maximum axial length at an angular magnification of one. The first component needs the largest light diameter. The diameter of this component reaches its largest value when the angular increase approaches unity. The obtained results make it possible to analytically carry out a parametric synthesis of three-component zoom-afocal systems, taking into account the requirements for their dimensions, the range of changes in the angular magnification and the permissible vignetting of the beam beams from the edge of the field of view.

Single-shot electron radiography using a laser–plasma accelerator

Contact and projection electron radiography of static targets was demonstrated using a laser–plasma accelerator driven by a kilojoule, picosecond-class laser as a source of relativistic electrons with an average energy of 20 MeV. Objects with areal densities as high as 7.7 g/cm2 were probed in materials ranging from plastic to tungsten, and radiographs with resolution as good as 90 μm were produced. The effects of electric fields produced by the laser ablation of the radiography objects were observed and are well described by an analytic expression relating imaging magnification change to electric-field strength.

Measurement of Crosshair Shift on Magnification Change in Field-Conditions

Crosshair shift with changing magnification of VIS camera is investigated in this article. The shift is a real problem that can significantly worsen fire-control system performance. The main condition of this measurement is ability to perform it on mounted devices in real fire-control system in field condition, it means that the measurement is adjusted to be done with accessible equipment. To measure this shift it is important to design target image which enables the shift measurement. Inaccuracy of this measurement is also discussed. The theoretical solution of the problem is demonstrated on experimental measurement.

Assessment of Maxillary First Molars Rotation in Class II malocclusion cases: A Cross Sectional Study

Introduction: Determination of malocclusion including individual tooth malposition is crucial during diagnosis and treatment planning. Along with anteroposterior mal-relation, there is often the rotation of upper first molars in Class II cases. Rotated molars not only occupy more space than normally positioned molars but also increase the challenge for orthodontic treatment. Aims and objectives: This study aimed to determine the prevalence and extent of maxillary molar rotation in Class II division 1 and 2 malocclusion cases. Material and Methods: A total of 142 pretreatment maxillary casts of Class II malocclusion (71 division 1 and 71 division 2) cases were collected from the Department of Orthodontics of People's Dental College and Hospital. All the casts were scanned at a 1 200 dpi resolution with teeth touching the glass of the scanner (brother MFC-L2700DW model). Scanned pictures were then printed without any change in magnification. Measurement was made on those printed copies of casts. To determine the rotation and its severity a method developed by Ricketts (Line of Ricketts) was used. Descriptive analysis was carried out in Microsoft Excel 2013. Result: In Class II division 1 cases, 45 (63.4%) had right molar rotation and 47 (66.2%) had left molar rotation. In Class II division 2 cases, 33 (46.5%) had right molar rotation while 34 (47.9%) had left molar rotation. Similarly, the mean rotations of the right and left molars in division 1 were 6.24 mm and 6.77 mm respectively and those in division 2 were 4.82 mm and 4.94 mm respectively. Conclusion: The prevalence and extent of rotation of maxillary molars in Class II divisions 1 and 2 malocclusion cases were assessed in this study. Mesiopalatal rotation and left molar rotation were observed more commonly in both divisions.

A Depth Sensor Based on Transient Property of Liquid Crystal Lens

The property of maintaining the lens state of the liquid crystal (LC) lens during the switching between positive and negative lens states is made use of in the fast acquirement of multi-focus images without magnification change. A depth from focus (DFF) pipeline that can generate a low-error depth map and an all-in-focus image is proposed. The depth of the scene is then obtained via DFF pipeline from the captured images. The depth sensor proposed in this paper has the advantages of simple structure, low cost, and long service life.

PiRamid: A compact Raspberry Pi imaging box to automate small-scale time-lapse digital analysis, suitable for laboratory and field use

Digital imaging permits the quantitation of many experiments, such as microbiological growth assays, but laboratory digital imaging systems can be expensive and too specialised. The Raspberry Pi camera platform makes automated, controlled imaging affordable with accessible customisation. When combined with open source software and open-source 3D printed hardware, the control over image quality and capture of this platform permits the rapid development of novel instrumentation. Here we present “PiRamid”, a compact, portable, and inexpensive enclosure for autonomous imaging both in the laboratory and in the field. The modular three-piece 3D printed design makes it easy to incorporate different camera systems or lighting configurations (e.g., single wavelength LED for fluorescence). The enclosed design allows complete control of illumination unlike a conventional digital camera or smartphone, on a tripod or handheld, under ambient lighting. The stackable design permits rapid sample addition or camera focus adjustment, with a corresponding change in magnification and resolution. The entire unit is small enough to fit within a microbiological incubator, and cheap enough (∼£100) to scale out for larger parallel experiments. Simply, Python scripts fully automate illumination and image capture for small-scale experiments with an ∼110×85 mm area at 70–90 µm resolution. We demonstrate the versatility of PiRamid by capturing time-resolved, quantitative image data for a wide range of assays. Bacterial growth kinetics was captured for conventional microbiology (agar Petri dishes), 3D printed custom microbiology labware and microfluidic microbiology. To illustrate application beyond microbiology, we demonstrate time-lapse imaging of crystal growth and degradation of salad leaves. Minor modifications permit epi-illumination by addition of a LED ring to the camera module. We conclude that PiRamid permits inexpensive digital capture and quantitation of a wide range of experiments by time-lapse imaging to simplify both laboratory and field imaging.

Radial and Tangential Retinal Magnifications as Functions of Visual Field Angle Across Spherical, Oblate, and Prolate Retinal Profiles.

PurposeTo provide a tool for calculating radial and tangential retinal magnifications as functions of field angle and retinal shape and to articulate patterns of magnification across the retina for monocular and binocular combinations of prolate-, oblate-, and spherical-shaped retinas.MethodsFormulae were derived to calculate radial and tangential retinal magnifications (mm/deg) from field angle (degrees), retinal asphericity (unitless conic constant), retinal vertex radius of curvature (mm), and nodal point position (mm). Monocular retinal magnifications were determined for eyes with prolate, spherical, and oblate retinas as functions of field angle. Bilateral differences in magnifications were examined for combinations of those eyes.ResultsRetinal shape substantially affects magnification profiles even for eyes with the same axial length. Greatest magnification changes across a retina and between eyes, as well as greatest increase in radial–tangential differences (distortion), occur with prolate retinas. Binocular magnification differences were smallest for oblate retinas. Nodal points anterior to the vertex center of curvature and oblate asphericity both cause field-dependent reductions in magnification relative to the fovea (barrel distortion), whereas nodal points posterior to vertex center of curvature and prolate asphericity cause the opposite (pincushion distortion). Retinal magnification differences due to eye shape are much greater than aniseikonia thresholds and chromatic differences in magnification. A spreadsheet tool implements the magnification calculations.ConclusionsLocal retinal magnifications as functions of field angle have substantial effects on objective applications (imaging retinal anatomy) and subjective experiences (aniseikonia) and quantify an ocular property that differs across eye shapes and refractive errors.Translational RelevanceMethods are provided to customize the calculation of radial and tangential magnifications across the retina for individual eyes, which will bolster the multifactorial study of the effects of foveal and peripheral optics across eye shapes and refractive errors.

Patient's posteroanterior chest radiographs are routinely displayed at different sizes on PACS: Cause and prevalence

ObjectiveSequential posteroanterior chest radiographs (CXRs) on any one patient are commonly displayed at different sizes on PACS monitors. The purpose of this study was to determine the cause of these differences, the percentage of radiographs affected, the relative change in magnification seen and if radiologists were aware of this display difference. MethodsDifferences in routine radiographer collimation pre-acquisition and image cropping (shuttering) post acquisition were noted. From three different hospitals, 300 posteroanterior (PA) erect CXRs with prior comparative studies were viewed side-by-side on a standard landscape display monitor. Variation in display size was calculated using the number of detector elements in the autofitted axis of the radiograph, when compared with the prior study. Correlation between patient gender and extent of magnification between images was recorded. Following this, a national survey was circulated to see if radiologists were aware of this phenomenon. ResultsLarge variations in display size were noted. The mean extent of magnification between sequential PA chest radiographs was ±6.8% (range 0–21.6%). 98% of CXRs had some degree of variability in display size. There was no significant difference in the extent of variation in magnification based on age or gender. 86% of the radiologists who responded to the survey (n = 132) were unaware of any display size variability. ConclusionSequential DR acquired chest radiographs are routinely displayed with varying degrees of magnification on PACS monitors due to differences in radiographer practice and auto-fit display settings. Most radiologists surveyed were unaware of these differences and their causation.

Field-of-view correction in a VR HMD display with varifocal optics

Nowadays, we observe a progressive increase amount of virtual technologies application. VR devices, i.e. HMDs, are still struggling with the VAC. It is possible to “implement” the accommodation mechanism in HMDs using a varifocal system. By using focus tuneable lenses, we achieve high speed and smoothness of displacement of the virtual image plane. This solution involves also unfavourable changes of geometrical parameters of the projected image i.e. change in magnification. This can be solved by software modification parameters of the virtual camera. In this paper, the developed construction of varifocal HMD is presented, including the method of maintaining the constancy magnification. Full Text: PDF ReferencesY-J. Wang , Y-H. Lin, "Liquid crystal technology for vergenceaccommodation conflicts in augmented reality and virtual reality systems: a review", Liq. Cryst. Rev. 9. 35 (2021). CrossRef P.P. Monticone, M. Menozzi, M. Schlup, "Instrument for high-speed recording of accommodation of the human eye", Biomed. Tech. 55: 83 (2010). CrossRef G. Kramida, "Resolving the vergence-accommodation confict in headmounted displays", IEEE Trans. Vis. Comput. Graph. 22, 1912 (2016). CrossRef S. Shiwa, K. Omura, and F. Kishino, "Proposal for a 3-D display with accommodative compensation: 3DDAC," J. Soc. Inf. Disp. 4, 255 (1996). CrossRef K. Rathinavel, G. Wetzstein, H. Fuchs, "Varifocal Occlusion-Capable Optical See-through Augmented Reality Display based on Focus-tunable Optics," IEEE Trans. Vis. Comput. Graph. 25, 3125 (2019). CrossRef