Dynamic measurement of accommodation and pupil size using the portable Grand Seiko FR-5000 autorefractor

PURPOSE. The purpose of this study was to evaluate the potential of the portable Grand Seiko FR-5000 autorefractor to allow objective, continuous, open-field measurement of accommodation and pupil size for the investigation of the visual response to real-world environments and changes in the optical components of the eye. METHODS. The FR-5000 projects a pair of infrared horizontal and vertical lines on either side of fixation, analyzing the separation of the bars in the reflected image. The measurement bars were turned on permanently and the video output of the FR-5000 fed into a PC for real-time analysis. The calibration between infrared bar separation and the refractive error was assessed over a range of 10.0 D with a model eye. Tolerance to longitudinal instrument head shift was investigated over a ±15 mm range and to eye alignment away from the visual axis over eccentricities up to 25.0°. The minimum pupil size for measurement was determined with a model eye. RESULTS. The separation of the measurement bars changed linearly (r = 0.99), allowing continuous online analysis of the refractive state at 60 Hz temporal and approximately 0.01 D system resolution with pupils >2 mm. The pupil edge could be analyzed on the diagonal axes at the same rate with a system resolution of approximately 0.05 mm. The measurement of accommodation and pupil size were affected by eccentricity of viewing and instrument focusing inaccuracies. CONCLUSIONS. The small size of the instrument together with its resolution and temporal properties and ability to measure through a 2 mm pupil make it useful for the measurement of dynamic accommodation and pupil responses in confined environments, although good eye alignment is important. Copyright © 2006 American Academy of Optometry.

Eye essentials:visual fields

This book covers the essentials of visual field measurement from the anatomical concepts of the visual pathway and how they relate to visual field loss to the measurement and analysis of visual fields. Eye Essentials is a major new series which provides authoritative and accessible information for all eye care professionals, whether in training or in practice. Each book is a rapid revision aid for students taking higher professional qualifications and a handy clinical reference guide for practitioners in busy clinics. Highly designed with synoptic text, handy tables, key bullet points, summaries, icons and stunning full colour illustrations, the books have rapidly established themselves as the essential eye clinic pocket books.

Highly sensitive refractive index sensor based on cascaded microfiber knots with Vernier effect

We propose and experimentally demonstrate a refractive index (RI) sensor based on cascaded microfiber knot resonators (CMKRs) with Vernier effect. Deriving from high proportional evanescent field of microfiber and spectrum magnification function of Vernier effect, the RI sensor shows high sensitivity as well as high detection resolution. By using the method named "Drawing-Knotting-Assembling (DKA)", a compact CMKRs is fabricated for experimental demonstration. With the assistance of Lorentz fitting algorithm on the transmission spectrum, sensitivity of 6523nm/RIU and detection resolution up to 1.533 x 10-7 RIU are obtained in the experiment which show good agreement with the numerical simulation. The proposed all-fiber RI sensor with high sensitivity, compact size and low cost can be widely used for chemical and biological detection, as well as the electronic/magnetic field measurement

The use of an energy analyser for the measurement of the total energy distribution of field-emitted electrons from tungsten

DUE TO COPYRIGHT RESTRICTIONS ONLY AVAILABLE FOR CONSULTATION AT ASTON UNIVERSITY LIBRARY AND INFORMATION SERVICES WITH PRIOR ARRANGEMENT

Sampling and measurement methods for a study of childhood refractive error in a UK population

Background There is a paucity of data describing the prevalence of childhood refractive error in the United Kingdom. The Northern Ireland Childhood Errors of Refraction study, along with its sister study the Aston Eye Study, are the first population-based surveys of children using both random cluster sampling and cycloplegic autorefraction to quantify levels of refractive error in the United Kingdom. Methods Children aged 6–7 years and 12–13 years were recruited from a stratified random sample of primary and post-primary schools, representative of the population of Northern Ireland as a whole. Measurements included assessment of visual acuity, oculomotor balance, ocular biometry and cycloplegic binocular open-field autorefraction. Questionnaires were used to identify putative risk factors for refractive error. Results 399 (57%) of 6–7 years and 669 (60%) of 12–13 years participated. School participation rates did not vary statistically significantly with the size of the school, whether the school is urban or rural, or whether it is in a deprived/non-deprived area. The gender balance, ethnicity and type of schooling of participants are reflective of the Northern Ireland population. Conclusions The study design, sample size and methodology will ensure accurate measures of the prevalence of refractive errors in the target population and will facilitate comparisons with other population-based refractive data.

Neuroimaging and psychophysiological measurement in organizational research:an agenda for research in organizational cognitive neuroscience

Although organizational research has made tremendous strides in the last century, recent advances in neuroscience and the imaging of functional brain activity remain underused. In fact, even the use of well-established psychophysiological measurement tools is comparatively rare. Following the lead of social cognitive neuroscience, in this review, we conceptualize organizational cognitive neuroscience as a field dedicated to exploring the processes within the brain that underlie or influence human decisions, behaviors, and interactions either (a) within organizations or (b) in response to organizational manifestations or institutions. We discuss organizational cognitive neuroscience, bringing together work that may previously have been characterized rather atomistically, and provide a brief overview of individual methods that may be of use. Subsequently, we discuss the possible convergence and integration of the different neuroimaging and psychophysiological measurement modalities. A brief review of prior work in the field shows a significant need for a more coherent and theory-driven approach to organizational cognitive neuroscience. In response, we discuss a recent example of such work, along with three hypothetical case studies that exemplify the link between organizational and psychological theory and neuroscientific methods.

Emergent strategy and the measurement of performance:the formulation of performance indicators at the microlevel

This article presents some evidence on an aspect of the design of a strategic control system, at the microlevel, within a single organization. The research we report used an ethnographic approach to provide an understanding of strategy formulation. Our aim is to contribute to an area of literature which is of increasing significance, but relatively underdeveloped in terms of the application of in-depth, field-research techniques. We take an intensive look at the manner in which performance measures are formulated, at the microlevel, within a single organization. The article presents, as an in-depth case analysis, the experience of a fisheries holding company in New Zealand. The article recounts the experiences of managers within the organization of the process of identification of such things as critical success factors and key performance indicators (KPIs) and, more broadly, the formulation of a strategic performance measurement system.

The frontier approach to the measurement of productivity and technical efficiency

In 1957, Farrell proposed to measure technical (in)efficiency as the realised deviation from a frontier isoquant. Since then, the research has developed several methods to derive the production frontier and it has also extended its scope in applying frontier techniques to the measurement of total factor productivity. In this paper, I present the core techniques for the measurement of technical efficiency and productivity based on the notion of frontier and introduce the more recent technological advances in the field.

The impact of performance measurement in strategic planning

Purpose – To investigate the impact of performance measurement in strategic planning process. Design/methodology/approach – A large scale survey was conducted online with Warwick Business School alumni. The questionnaire was based on the Strategic Development Process model by Dyson. The questionnaire was designed to map the current practice of strategic planning and to determine its most influential factors on the effectiveness of the process. All questions were close ended and a seven-point Likert scale used. The independent variables were grouped into four meaningful factors by factor analysis (Varimax, coefficient of rotation 0.4). The factors produced were used to build regression models (stepwise) for the five assessments of strategic planning process. Regression models were developed for the totality of the responses, comparing SMEs and large organizations and comparing organizations operating in slowly and rapidly changing environments. Findings – The results indicate that performance measurement stands as one of the four main factors characterising the current practice of strategic planning. This research has determined that complexity coming from organizational size and rate of change in the sector creates variation in the impact of performance measurement in strategic planning. Large organizations and organizations operating in rapidly changing environments make greater use of performance measurement. Research limitations/implications – This research is based on subjective data, therefore the conclusions do not concern the impact of strategic planning process' elements on the organizational performance achievements, but on the success/effectiveness of the strategic planning process itself. Practical implications – This research raises a series of questions about the use and potential impact of performance measurement, especially in the categories of organizations that are not significantly influenced by its utilisation. It contributes to the field of performance measurement impact. Originality/value – This research fills in the gap literature concerning the lack of large scale surveys on strategic development processes and performance measurement. It also contributes in the literature of this field by providing empirical evidences on the impact of performance measurement upon the strategic planning process.

Performance measurement based co-ordination of enterprise resource planning systems in a virtual enterprise

As the backbone of e-business, Enterprise Resource Planning (ERP)system plays an important role in today's competitive business environment. Few publications discuss the application of ERP systems in a virtual enterprise (VE). A VE is defined as a dynamic partnership among enterprises that can bring together complementary core competencies needed to achieve a business task. Since VE strongly emphasises partner cooperation, specific issues exist relative to the implementation of ERP systems in a VE. This paper discusses the use of VE Performance Measurement System(VEPMS) to coordinate ERP systems of VE partners. It also defines the framework of a `Virtual Enterprise Resource Planning (VERP) system', and identifies research avenues in this field.

Continuous measurement of accommodation in human factor applications

It has long been sought to measure ocular accommodation continuously in human factor applications such as driving or flying. Open-field autorefractors such as the Canon R-1 could be converted to allow continuous, objective recording, but steady eye fixation and head immobilisation were essential for the measurements to be valid. Image analysis techniques utilised by newer open-view autorefractors such as the Shin-Nippon SRW-5000 are more tolerant to head and eye movements, but perhaps the technique with the greatest potential for the measurement of accommodation in human factor applications is photoretinoscopy. This paper examines the development of techniques for high temporal measurements of accommodation and reports on the tolerance of one such recent commercial instrument, the PowerRefractor (PlusOptiX). The instrument was found to be tolerant to eye movements from the optical axis of the instrument (∼0.50 DS change in apparent accommodation with gaze 25° eccentric to the optical axis), longitudinal head movement (<0.25 DS from 8 cm towards and 20 cm away from the correct photorefractor to eye distance) and changes in background illuminance (<0.25 DS from 0.5 to 20 cd m-2 target luminance). The PowerRefractor also quantifies the direction of gaze and pupil size, but is unable to take measurements with small pupils <3.7 ±1.0 mm. © 2002 The College of Optometrists.

Investigation of some critical aspects of on-line surface measurement by a wavelength-division-multiplexing technique

Some critical aspects of a new kind of on-line measurement technique for micro and nanoscale surface measurements are described. This attempts to use spatial light-wave scanning to replace mechanical stylus scanning, and an optical fibre interferometer to replace optically bulky interferometers for measuring the surfaces. The basic principle is based on measuring the phase shift of a reflected optical signal. Wavelength-division-multiplexing and fibre Bragg grating techniques are used to carry out wavelength-to-field transformation and phase-to-depth detection, allowing a large dynamic measurement ratio (range/resolution) and high signal-to-noise ratio with remote access. In effect the paper consists of two parts: multiplexed fibre interferometry and remote on-machine surface detection sensor (an optical dispersive probe). This paper aims to investigate the metrology properties of a multiplexed fibre interferometer and to verify its feasibility by both theoretical and experimental studies. Two types of optical probes, using a dispersive prism and a blazed grating, respectively, are introduced to realize wavelength-to-spatial scanning.

A pragmatic Bayesian approach to wind field retrieval

The ERS-1 Satellite was launched in July 1991 by the European Space Agency into a polar orbit at about 800 km, carrying a C-band scatterometer. A scatterometer measures the amount of backscatter microwave radiation reflected by small ripples on the ocean surface induced by sea-surface winds, and so provides instantaneous snap-shots of wind flow over large areas of the ocean surface, known as wind fields. Inherent in the physics of the observation process is an ambiguity in wind direction; the scatterometer cannot distinguish if the wind is blowing toward or away from the sensor device. This ambiguity implies that there is a one-to-many mapping between scatterometer data and wind direction. Current operational methods for wind field retrieval are based on the retrieval of wind vectors from satellite scatterometer data, followed by a disambiguation and filtering process that is reliant on numerical weather prediction models. The wind vectors are retrieved by the local inversion of a forward model, mapping scatterometer observations to wind vectors, and minimising a cost function in scatterometer measurement space. This thesis applies a pragmatic Bayesian solution to the problem. The likelihood is a combination of conditional probability distributions for the local wind vectors given the scatterometer data. The prior distribution is a vector Gaussian process that provides the geophysical consistency for the wind field. The wind vectors are retrieved directly from the scatterometer data by using mixture density networks, a principled method to model multi-modal conditional probability density functions. The complexity of the mapping and the structure of the conditional probability density function are investigated. A hybrid mixture density network, that incorporates the knowledge that the conditional probability distribution of the observation process is predominantly bi-modal, is developed. The optimal model, which generalises across a swathe of scatterometer readings, is better on key performance measures than the current operational model. Wind field retrieval is approached from three perspectives. The first is a non-autonomous method that confirms the validity of the model by retrieving the correct wind field 99% of the time from a test set of 575 wind fields. The second technique takes the maximum a posteriori probability wind field retrieved from the posterior distribution as the prediction. For the third technique, Markov Chain Monte Carlo (MCMC) techniques were employed to estimate the mass associated with significant modes of the posterior distribution, and make predictions based on the mode with the greatest mass associated with it. General methods for sampling from multi-modal distributions were benchmarked against a specific MCMC transition kernel designed for this problem. It was shown that the general methods were unsuitable for this application due to computational expense. On a test set of 100 wind fields the MAP estimate correctly retrieved 72 wind fields, whilst the sampling method correctly retrieved 73 wind fields.

Non-standard techniques for the investigation of the visual field

The study investigated the potential applications and the limitations of non-standard techniques of visual field investigation utilizing automated perimetry. Normal subjects exhibited a greater sensitivity to kinetic stimuli than to static stimuli of identical size. The magnitude of physiological SKD was found to be largely independent of age, stimulus size, meridian and eccentricity. The absence of a dependency on stimulus size indicated that successive lateral spatial summation could not totally account for the underlying mechanism of physiological SKD. The visual field indices MD and LV exhibited a progressive deterioration during the time course of a conventional central visual field examination both for normal subjects and for ocular hypertensive patients. The fatigue effect was more pronounced in the latter stages and for the second eye tested. The confidence limits for the definition of abnormality should reflect the greater effect of fatigue on the second eye. A 330 cdm-2 yellow background was employed for blue-on-yellow perimetry. Instrument measurement range was preserved by positioning a concave mirror behind the stimulus bulb to increase the light output by 60% . The mean magnitude of SWS pathway isolation was approximately 1.4 log units relative to a 460nm stimulus filter. The absorption spectra of the ocular media exhibited an exponential increase with increase in age, whilst that of the macular pigment showed no systematic trend. The magnitude of ocular media absorption was demonstrated to reduce with increase in wavelength. Ocular media absorption was significantly greater in diabetic patients than in normal subjects. Five diabetic patients with either normal or borderline achromatic sensitivity exhibited an abnormal blue-on-yellow sensitivity; two of these patients showed no signs of retinopathy. A greater vulnerability of the SWS pathway to the diabetic disease process was hypothesized.

Rough-terrain groundspeed measurement:a radar-based commercial solution

Off-highway motive plant equipment is costly in capital outlay and maintenance. To reduce these overheads and increase site safety and workrate, a technique of assessing and limiting the velocity of such equipment is required. Due to the extreme environmental conditions met on such sites, conventional velocity measurement techniques are inappropriate. Ogden Electronics Limited were formed specifically to manufacture a motive plant safety system incorporating a speed sensor and sanction unit; to date, the only such commercial unit available. However, problems plague the reliability, accuracy and mass production of this unit. This project assesses the company's exisiting product, and in conjunction with an appreciation of the company history and structure, concludes that this unit is unsuited to its intended application. Means of improving the measurement accuracy and longevity of this unit, commensurate with the company's limited resources and experience, are proposed, both for immediate retrofit and for longer term use. This information is presented in the form of a number of internal reports for the company. The off-highway environment is examined; and in conjunction with an evaluation of means of obtaining a returned signal, comparisons of processing techniques, and on-site gathering of previously unavailable data, preliminary designs for an alternative product are drafted. Theoretical aspects are covered by a literature review of ground-pointing radar, vehicular radar, and velocity measuring systems. This review establishes and collates the body of knowledge in areas previously considered unrelated. Based upon this work, a new design is proposed which is suitable for incorporation into the existing company product range. Following production engineering of the design, five units were constructed, tested and evaluated on-site. After extended field trials, this design has shown itself to possess greater accuracy, reliability and versatility than the existing sensor, at a lower unit cost.