1,720,996 research outputs found
Comparison of the handheld RETeval ERG system with a routine ERG system in healthy adults and in paediatric patients
No full textBackground: Electroretinograms (ERG) are necessary for the evaluation of retinal function, however testing children is challenging and only performed at a few specialised centres. The handheld RETeval ERG instrument could prove a valuable tool for clinicians in assessing retinal function. This study evaluates this device using an ISCEV approved modified paediatric protocol and compares it to standard methods using a photic stimulator. Subjects and Method: Cone and rod ERGs were recorded using a standard photic stimulator (Grass) and the RETeval device. Both methods involve using skin electrodes, without mydriasis and under dark and light conditions. Two groups of participants were recruited: 44 healthy adult subjects (mean age =39 years) and 37 paediatric patients (mean=5 years). Three of the paediatric patients were not sufficiently compliant to undertake the RETeval recording.Results: Adult ERG reference range data is presented for the RETeval and compared to the standard system. There is lack of absolute agreement in the measurements between the two devices, highlighting the need for device-specific reference data. In the paediatric group there is a high level of diagnostic agreement between both systems (Cohen’s Kappa k = 0.80). The relative sensitivity and specificity of the RETeval was 1.0 and 0.91. Qualitative patient and user feedback is discussed. Conclusions: ERGs are similar between the two methodologies. This study demonstrates that the RETeval device is a useful tool for assessing retinal function in children. Importantly, it is quick, relatively easy to use and can potentially reduce the burden and costs of paediatric electrodiagnostic assessments. A Correction was issued to figure 1 of this paper shortly after publication due to typographical error. The correction can be accessed at the original paper, the additional links on this record and the correction pdf. Pease use figure 1 in the correction not the Accepted Manuscript
Use of a handheld electrophysiology device (RETeval, LKC) to identify visual pathway decussation defects
No full textElectrodiagnostic testing (EDTs) require large equipment and trained clinical scientists so are restricted to specialist centres, and often have long waiting lists. Pattern and flash visual evoked potentials (fVEP) have been utilised in the assessment of visual pathway integrity, including chiasmal anomalies in albinism. In this qualitative clinical study, we assess the potential of the handheld RETeval to screen for excess nerve decussation and other post-chiasmal defects
Use of a handheld electrophysiology device (RETeval, LKC) to identify visual pathway decussation defects
No full textPurpose : electrodiagnostic testing (EDTs) require large equipment and trained clinical scientists so are restricted to specialist centres, and often have long waiting lists. Pattern and flash visual evoked potentials (fVEP) have been utilised in the assessment of visual pathway integrity, including chiasmal anomalies in albinism. In this qualitative clinical study, we assess the potential of the handheld RETeval to screen for excess nerve decussation and other post-chiasmal defects.Methods : 18 patients with suspected albinism or retro-chiasmal lesions (aged 0-15yrs, mean 5) were selected from those undergoing routine EDTs at a regional referral centre. Standard paediatric EDTs were performed, followed by fVEP using the RETeval. Control data was collected from 12 volunteers (aged 26-54yrs, mean 32). Right and left occipital electrodes were placed midway between Oz (10-20 system) and either ear. The ground electrode was placed at Fz. FVEPs of 3cd.s/m2 were recorded from 10 brief (<5ms) 1Hz flashes. The left occipital VEP waveform was subtracted from that of the right occiput, creating a single channel response for each eye separately. RETeval data was compared to results obtained from the standard paediatric protocol using a photic stimulator (Grass PS 22). Pearson’s correlation was used to calculate the extent of asymmetry, where a value of -1 showed complete asymmetry whilst a value of +1 showed absolute symmetry in occipital VEP distribution. Data between controls and patients were compared using a Mann-Whitney U test.Results : FVEP testing using both the standard protocol and the RETeval identified asymmetry in 11 patients with suspected albinism. The Pearsons correlate of the albinism cohort (-0.504 ± 0.208) was compared to the control data (0.184 ± 0.339) and a Mann-Whitney U test showed a significant difference between the two groups (p<0.001). This demonstrates the effectiveness of the RETeval in detecting crossed asymmetry secondary to excessive nerve decussation in albinism. The RETeval also detected 7 cases of left and right retro-chiasmal lesions that showed an uncrossed asymmetry.Conclusions : this study adds to the growing body of work investigating the use of the handheld RETeval device for prioritising patients waiting for in-depth EDTs. This data shows the RETeval has the potential to be used as a screening tool for the detection of chiasmal and retro-chiasmal anomalies.<br/
Eyetracking-enhanced VEP for nystagmus
No full textVisual evoked potential (VEP) testing is an essential first stage in the diagnostic workup of patients with infantile nystagmus (IN). VEPs are an important factor in the diagnosis of albinism, which accompanies IN in ~28% of cases, as well as chiasmal, optic nerve and neurometabolic disease that can all present with IN. VEPs are also used to assess prognostic visual ability in cases of retinal dystrophy and optic nerve disease. Despite being used regularly in those with IN, VEP testing requires patients to keep the eyes still; something that people with IN naturally cannot do. Fixation instability during VEP testing is believed to reduce VEP signal amplitude, and as a result, the reliability of VEP may be reduced in one of the patient groups that needs it the most. This study investigates whether VEP signal quality (amplitude) can be improved in people with IN, by triggering acquisition only during the foveating (slow) periods of the nystagmus waveform
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
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