The investigation of the sensitivity gradient of the visual field, as a function of stimulus dynamic range, in the normal and abnormal eye

The study utilized the advanced technology provided by automated perimeters to investigate the hypothesis that patients with retinitis pigmentosa behave atypically over the dynamic range and to concurrently determine the influence of extraneous factors on the format of the normal perimetric sensitivity profile. The perimetric processing of some patients with retinitis pigmentosa was considered to be abnormal in either the temporal and/or the spatial domain. The standard size III stimulus saturated the central regions and was thus ineffective in detecting early depressions in sensitivity in these areas. When stimulus size was scaled in inverse proportion to the square root of ganglion cell receptive field density (M-scaled), isosensitive profiles did not result, although cortical representation was theoretically equivalent across the visual field. It was conjectured that this was due to variations in the ganglion cell characteristics with increasing peripheral angle, most notably spatial summation. It was concluded that the development of perimetric routines incorporating stimulus sizes adjusted in proportion to the coverage factor of retinal ganglion cells would enhance the diagnostic capacity of perimetry. Good general and local correspondence was found between perimetric sensitivity and the available retinal cell counts. Intraocular light scatter arising both from simulations and media opacities depressed perimetric sensitivity. Attenuation was greater centrally for the smaller LED stimuli, whereas the reverse was true for the larger projected stimuli. Prior perimetric experience and pupil size also demonstrated eccentricity-dependent effect on sensitivity. Practice improved perimetric sensitivity for projected stimuli at eccentricities greater than or equal to 30o; particularly in the superior region. Increase in pupil size for LED stimuli enhanced sensitivity at eccentricities greater than 10o. Conversely, microfluctuation in the accommodative response during perimetric examination and the correction of peripheral refractive error had no significant influence on perimetric sensitivity.

The abstracts of the 5th UQ symposium on organisational psychology 4 June 2005 Emmanuel College, University of Queensland, organised and sponsored by the Centre for Organisational Psychology, University of Queensland

These abstracts form the collection of papers that were presented at the 5th UQ Symposium on Organisational Psychology held at Emmanuel College, University of Queensland, Brisbane, on Saturday 4th June, 2005. The UQ Symposium on Organisational Psychology is an annual event organised by the Centre for Organisational Psychology at the University of Queensland. The aim of the symposium is for academic psychologists to present their latest research to fellow academics and practitioners. Papers were accepted for either paper presentation or poster presentation following a peer-review process. The 75 delegates who attended consisted of practitioners and academics. The inter-state invited speakers were Professor John Cordery (University of Western Australia) and Dr Leisa Sargent (University of Melbourne). The inter-state student speaker was Michelle Pizer (Deakin University). For more information about the UQ Symposium on Organisational Psychology series please contact Robin Martin (r.martin@psy.uq.edu.au).

Analysis of variables measured in the visual screening of University of Birmingham freshmen and a critical review of visual screening methods and approach

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Acquirer and owner perceptions of technology integration:the South African case

Developing countries are subject to the same global pressures as their developed counterparts but have additional domestic challenges that may place them at a significant, and perhaps insurmountable, disadvantage. However, technology still offers them the opportunity to participate in the international economy. Difficult conditions in their countries do not absolve managers from formulating and implementing technology policies that can make their firms globally competitive. At a macro-economic level, a number of broad developmental issues impact on the use of technology in developing countries. The subject of this paper is to examine the challenge for South African firms in their efforts to master technology, despite internal and external difficulties. Owners of technology need to consider the local context when supplying their technology to developing markets. The paper aims to investigate the views of technology recipients by examining the perceptions of South African managers regarding technology integration in a manufacturing environment. A number of technology suppliers were also interviewed in order to obtain their opinions on the issues raised by the technology acquirers. The importance of different factors in integrating technology is studied in relation to managers ’ abilities to control these variables. An importance-control grid framework is used to identify critical parameters and to assess how they can be managed in a complex environment.

Comparison of near visual acuity and reading metrics in presbyopia correction

PURPOSE: To provide a consistent standard for the evaluation of different types of presbyopic correction. SETTING: Eye Clinic, School of Life and Health Sciences, Aston University, Birmingham, United Kingdom. METHODS: Presbyopic corrections examined were accommodating intraocular lenses (IOLs), simultaneous multifocal and monovision contact lenses, and varifocal spectacles. Binocular near visual acuity measured with different optotypes (uppercase letters, lowercase letters, and words) and reading metrics assessed with the Minnesota Near Reading chart (reading acuity, critical print size [CPS], CPS reading speed) were intercorrelated (Pearson product moment correlations) and assessed for concordance (intraclass correlation coefficients [ICC]) and agreement (Bland-Altman analysis) for indication of clinical usefulness. RESULTS: Nineteen accommodating IOL cases, 40 simultaneous contact lens cases, and 38 varifocal spectacle cases were evaluated. Other than CPS reading speed, all near visual acuity and reading metrics correlated well with each other (r>0.70, P<.001). Near visual acuity measured with uppercase letters was highly concordant (ICC, 0.78) and in close agreement with lowercase letters (+/- 0.17 logMAR). Near word acuity agreed well with reading acuity (+/- 0.16 logMAR), which in turn agreed well with near visual acuity measured with uppercase letters 0.16 logMAR). Concordance (ICC, 0.18 to 0.46) and agreement (+/- 0.24 to 0.30 logMAR) of CPS with the other near metrics was moderate. CONCLUSION: Measurement of near visual ability in presbyopia should be standardized to include assessment of near visual acuity with logMAR uppercase-letter optotypes, smallest logMAR print size that maintains maximum reading speed (CPS), and reading speed. J Cataract Refract Surg 2009; 35:1401-1409 (C) 2009 ASCRS and ESCRS

An Investigation into the adoption and implementation of computer aided production management systems:using the Rogers model of adoption and implementation and a social constuctionist account of technology

The research investigates the processes of adoption and implementation, by organisations, of computer aided production management systems (CAPM). It is organised around two different theoretical perspectives. The first part is informed by the Rogers model of the diffusion, adoption and implementation of innovations, and the second part by a social constructionist approach to technology. Rogers' work is critically evaluated and a model of adoption and implementation is distilled from it and applied to a set of empirical case studies. In the light of the case study data, strengths and weaknesses of the model are identified. It is argued that the model is too rational and linear to provide an adequate explanation of adoption processes. It is useful for understanding processes of implementation but requires further development. The model is not able to adequately encompass complex computer based technologies. However, the idea of 'reinvention' is identified as Roger's key concept but it needs to be conceptually extended. Both Roger's model and definition of CAPM found in the literature from production engineering tend to treat CAPM in objectivist terms. The problems with this view are addressed through a review of the literature on the sociology of technology, and it is argued that a social constructionist approach offers a more useful framework for understanding CAPM, its nature, adoption, implementation, and use. CAPM it is argued, must be understood on terms of the ways in which it is constituted in discourse, as part of a 'struggle for meaning' on the part of academics, professional engineers, suppliers, and users.

Acquisition and management of technology in Malaysian companies

This thesis is about the acquisition and diffusion of imported technology. Writers in the field of technology development in developing countries have always recognised that technical progress depends on the diffusion of imported technology and its applications to the provision of products and processes (Rosemberg, 1982). Despite the massive importation of technology by Malaysian companies, little effort has been made to study and understand the diffusion system in local companies. This study analyses: The problems associated with the acquisition of technology, highlighting the technology strategies adopted by the suppliers of technology; the diffusion pattern and key characteristics of the diffusion process; and major factors affecting the diffusion of technology. The policy implications are examined and the framework to manage the diffusion process within the enterprises is suggested. The findings indicated that the diffusion process is not one of passive acceptance but involves systematic efforts to acquire and diffuse the imported technology. A strong system of diffusion in companies had enabled a rapid diffusion of imported technology resulting in higher levels of technical capability. On the other hand, weakness in the company's diffusion system led to limited diffusion and slow technical progress. Characteristics of diffusion system are analysed and discussed extensively. The thesis attempts to develop the idea of `in-house system of diffusion' associated with the acquisition and development of imported technology. It argues for the development ofa stronger theoretical framework on the diffusion and development of technology particularly in countries like Malaysia which relies extensively on the importation of foreign technology.

The effects of vigabatrin of the visual system

This thesis considers the visual electrophysiological effects of vigabatrin (an anti-epileptic drug, which acts by increasing the levels of the inhibitory neurotransmitter GABA on the retina of the eye compared to the concentric visual field defects which have been found associated with the drug. Flash and pattern ERG's, EOG's multifocal ERG's (VERIS), flash and pattern VEP's and visual fields were tested. Although VEP's have been shown not to be affected by vigabatrin, these were recorded to complete the testing. Initially, of the eight vigabatrin patients with known visual field defects, 7 showed abnormally delayed 30Hz flicker a-wave latencies, 5 abnormally delayed 30Hz b-wave latencies and 6 abnormally low 30Hz amplitudes. Also 7 showed an abnormally prolonged latency of oscillatory potential 1 (OP1). The two patients taking vigabatrin at the time of testing showed low EOG Arden index values. The VERIS results correlated well with the severity of the visual field defects. Following this finding, eleven healthy subjects received vigabatrin over a 10-day period. No changes were seen in the visual fields, however, the photopic ERG b-wave latency significantly increased (although not to abnormal values). A matched pairs study with eleven vigabatrin, patients and eleven epileptic patients, who had never taken vigabatrin supported the findings of abnormal 30Hz flicker b-wave and OP latencies associated with vigabatrin, again with the VERIS results correlating to the severity of the visual field defect. The abnormal 30Hz flicker and VERIS responses indicate involvement of the cone photoreceptors and the OP's show an effect on the amacrine cells. The ERG increase in the photopic b-wave latency also suggests involvement of the bipolar cells, however, this effect and the reversible effect on the Arden index after cessation of the drug may be unrelated to the visual field defect. To conclude this thesis, a field specific VEP stimulus was developed to assess the retinal function in the peripheral field of paediatric patients. It comprises of a dartboard stimulus with a central 0-5 degree black and white chequered stimulus, a blank 5-30 degree annulus and a 30-60 degree peripheral chequered stimulus. When optimised on four vigabatrin patients it was found that no peripheral response can be evoked with a field loss exceeding 30-35 degrees. Co-operation was found to be successful in children as young as four years old.

Early visual detection of oriented line targets: spatial characteristics,and reference frames of early visual orientation-processing

The orientations of lines and edges are important in defining the structure of the visual environment, and observers can detect differences in line orientation within the first few hundred milliseconds of scene viewing. The present work is a psychophysical investigation of the mechanisms of early visual orientation-processing. In experiments with briefly presented displays of line elements, observers indicated whether all the elements were uniformly oriented or whether a uniquely oriented target was present among uniformly oriented nontargets. The minimum difference between nontarget and target orientations that was required for effective target-detection (the orientation increment threshold) varied little with the number of elements and their spatial density, but the percentage of correct responses in detection of a large orientation-difference increased with increasing element density. The differing variations with element density of thresholds and percent-correct scores may indicate the operation of more than one mechanism in early visual orientation-processIng. Reducing element length caused threshold to increase with increasing number of elements, showing that the effectiveness of rapid, spatially parallel orientation-processing depends on element length. Orientational anisotropy in line-target detection has been reported previously: a coarse periodic variation and some finer variations in orientation increment threshold with nontarget orientation have been found. In the present work, the prominence of the coarse variation in relation to finer variations decreased with increasing effective viewing duration, as if the operation of coarse orientation-processing mechanisms precedes the operation of finer ones. Orientational anisotropy was prominent even when observers lay horizontally and viewed displays by looking upwards through a black cylinder that excluded all possible visual references for orientation. So, gravitational and visual cues are not essential to the definition of an orientational reference frame for early vision, and such a reference can be well defined by retinocentric neural coding, awareness of body-axis orientation, or both.

A comparison between static and kinetic visual attention as a means of detecting age-related deterioration of the visual system and driving performance

A critical review of previous research revealed that visual attention tests, such as the Useful Field of View (UFOV) test, provided the best means of detecting age-related changes to the visual system that could potentially increase crash risk. However, the question was raised as to whether the UFOV, which was regarded as a static visual attention test, could be improved by inclusion of kinetic targets that more closely represent the driving task. A computer program was written to provide more information about the derivation of UFOV test scores. Although this investigation succeeded in providing new information, some of the commercially protected UFOV test procedures still remain unknown. Two kinetic visual attention tests (DRTS1 and 2), developed at Aston University to investigate inclusion of kinetic targets in visual attention tests, were introduced. The UFOV was found to be more repeatable than either of the kinetic visual attention tests and learning effects or age did not influence these findings. Determinants of static and kinetic visual attention were explored. Increasing target eccentricity led to reduced performance on the UFOV and DRTS1 tests. The DRTS2 was not affected by eccentricity but this may have been due to the style of presentation of its targets. This might also have explained why only the DRTS2 showed laterality effects (i.e. better performance to targets presented on the left hand side of the road). Radial location, explored using the UFOV test, showed that subjects responded best to targets positioned to the horizontal meridian. Distraction had opposite effects on static and kinetic visual attention. While UFOV test performance declined with distraction, DRTS1 performance increased. Previous research had shown that this striking difference was to be expected. Whereas the detection of static targets is attenuated in the presence of distracting stimuli, distracting stimuli that move in a structured flow field enhances the detection of moving targets. Subjects reacted more slowly to kinetic compared to static targets, longitudinal motion compared to angular motion and to increased self-motion. However, the effects of longitudinal motion, angular motion, self-motion and even target eccentricity were caused by target edge speed variations arising because of optic flow field effects. The UFOV test was more able to detect age-related changes to the visual system than were either of the kinetic visual attention tests. The driving samples investigated were too limited to draw firm conclusions. Nevertheless, the results presented showed that neither the DRTS2 nor the UFOV tests were powerful tools for the identification of drivers prone to crashes or poor driving performance.