1,721,020 research outputs found
Multifocal pupillographic objective perimetry in age-related maculopathy
No full textAge-related macular degeneration (AMD) is a multifactorial disease caused by the interaction of environmental and genetic factors (Rattner & Nathans, 2006). Prevalence data has identified AMD as the leading cause of visual impairment and blindness in the western world (Hawkins et al., 1999; Klein et al., 2007). Recent advances in retinal imaging have improved the detection of pathology, allowing for timely diagnosis, identification of prognostic factors and the monitoring of therapy to be made. However, the newer imaging modalities fail to provide information on retinal function leaving clinicians to rely on diagnostically poor examination techniques to determine a patient's change in visual function (Ivers et al., 2001). The purpose of this thesis was to investigate the effects of various stages of AMD on the pupillary response with the secondary aim of determining the diagnostic potential of multifocal pupillographic objective perimetry (mfPOP) in AMD.
Our investigation began with the determination of the optimal features for centrally directed stimuli in multifocal pupillography. To overcome the effects of saturation and achieve high signal to noise ratios from stimuli presented in the central visual field, we conducted a series of 3 experiments testing on normal subjects a range of stimulus presentation intervals, spatial densities, visual angles and luminances. We determined that longer stimulus presentation intervals with low resolution (24-region) non-overlapping layouts at a luminance of approximately 250 cd/m{u00B2} achieved the largest contraction amplitudes and shortest times to peak response. We utilized the optimal stimulus features determined from our initial investigation to conduct a series of clinical experiments on subjects with early and advanced stages AMD. We also wished to assess the ability of mfPOP to monitor the effect of treatment for exudative AMD over time.
Contrary to our preliminary study results in normals, our investigation of the effects of exudative AMD on retinal function measured by mfPOP identified higher resolution stimuli (44 region) with shorter presentation intervals to elicit the largest changes in pupillary responses. In addition, receiver operator characteristic (ROC) analysis confirmed this stimulus to be the most diagnostic. The results suggest that signal convergence elicited from large slow stimulus presentations reduces the effects of localized severe defects. A subsequent study examining retinal dysfunction following 3 months of ranibizumab therapy confirmed our previous results. What was striking was the revelation that prior to treatment, the delay of pupillary responses to multifocal stimuli were the most vulnerable in AMD, and demonstrated the largest improvement following the typical course of therapy. There was also evidence that peripheral hypersensitivity was predicative of good treatment outcomes as expressed by reductions in retinal thickness.
Our final experiment investigated the potential of mfPOP to identify subjects with early clinical signs of AMD with the aim of offering prognostic factors identifying patients at risk of rapid progression. Implementing a novel stimulus presentation technique we demonstrated temporal response impairment biased to the superior hemifield in early AMD subjects. Our results suggested that mfPOP may identify retinal dysfunction in eyes with preserved visual acuity and in the absence of clinically visible signs
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Book Review: Clinical Procedures in Primary Eye Care, 5th Edition
No full textDavid Elliott’s Clinical Procedures in Primary Eye Care continues its growing reputation of being one of the most well-known and trusted procedures textbooks in optometry. The first edition of this book was released in 1997 when we were undergraduate optometry students, and we were very thankful to have used that edition. During subsequent successive versions, this book has evolved substantially. The newly revised 5th edition of this valuable resource continues to be concise and is divided into nine chapters covering a wide range of commonly used clinical techniques in primary care optometry. Each chapter begins with an outline format which makes the pertinent information easy to follow and easy to locate. Optometry students will find this book helpful as they navigate the many potential examination techniques by providing evidence-based eye examination techniques in a very easy-to-read and understandable format
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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