1,720,957 research outputs found
Fluorescein and indocyanine green angiography after transpupillary thermotherapy of choroidal neovascularization. Early vascular changes
No full textUse of capsular tension ring in phacoemulsification. indications and technique
No full textThe capsular tension ring (CTR) was originally introduced to reinforce the zonule in eyes with zonular dehiscence and to prevent capsular phimosis in eyes at risk for postoperative capsular shrinkage. Since then, other designs and applications have been developed and described. Modified CTRs with shields can be used in eyes with iris coloboma. A CTR with loops is intended for scleral fixation. Studies are underway to determine if the presence of the CTR helps avoid or limit capsular opacification. A number of different insertion techniques with the aid of manipulators, injectors and traction sutures have been described. We have developed a technique that is particularly effective in cases of zonular dehiscence due to its low solicitation to the damaged bag
Effect of posture on the diurnal variation in clinically significant diabetic macular edema
No full textPURPOSE. To investigate the role of posture and other systemic factors in the diurnal variation of clinically significant diabetic macular edema (CSDME). METHODS. Ten eyes of 10 diabetic subjects with CSDME underwent four OCT foveal thickness measurements with Stratus-OCT at 9 AM and 12, 3, and 6 PM consecutively on two different days, with the subject in an upright position on one and in a recumbent position on the other. For the "recumbent-position" measurements, the patients were admitted the night before and remained in bed during the entire day of testing. Clinical laboratory results at baseline included HbA1c, urinary albumin, and serum creatinine. Refraction and Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity were also measured before each OCT measurement was taken. Variations in blood pressure, body temperature, plasma glucose, renin, aldosterone, and cortisol levels were measured and then correlated with macular thickness. RESULTS. Foveal thickening decreased in all cases over the course of the day. The decrease, however, was significantly greater for the upright-position measurements (relative mean +/- SD decrease of 20.6% +/- 6.5% in the upright position and 6.2% +/- 4.6% in the recumbent position). Visual acuity improved by at least 1 ETDRS line in three eyes in the upright position as opposed to only one eye in the recumbent position. There seemed to be no association between any of the systemic factors studied and foveal thickening, with the exception of cortisol. CONCLUSIONS. The results support the hypothesis that posture and hydrostatic pressure play a major role in determining time-related shifts in CSDME and suggest that the forces of Starling's law can in part, account for CSDME formation
Optical coherence tomography versus stereoscopic fundus photography or biomicroscopy for diagnosing diabetic macular edema: A systematic review
No full textPURPOSE. To review systematically the sensitivity and specificity of optical coherence tomography ( OCT) for diagnosing macular edema attributable to diabetic retinopathy compared with well-established gold standard tests such as fundus stereophotography or contact and noncontact fundus biomicroscopy. METHODS. Medline and Embase were searched electronically and six major ophthalmic journals from 1998 to 2006 were hand searched. Two reviewers independently assessed trial searches, studied quality with the QUADAS ( Quality Assessment of Diagnostic Accuracy Studies) checklist, and extracted data. The target disease was clinically significant macular edema ( CSME) according to Early Treatment of Diabetic Retinopathy Study ( ETDRS) criteria. A bivariate model was used to obtain summary estimates of sensitivity and specificity and fit a summary receiver operating characteristic ( ROC) curve. RESULTS. Fifteen studies were considered eligible. These studies were of good quality for most items of the QUADAS checklist, but most studies did not report masking of examiners and did not describe how withdrawals and undetermined results were treated. Seven studies included healthy control subjects, which could have artificially enhanced OCT diagnostic performance. All but one study included both eyes of the patients without taking into account the within-subject correlation in statistical analyses. Sensitivity and specificity data could be extracted from only 6 of 15 studies, because appropriate cross tabulations of index and reference tests were not reported by the others. In five of these studies, central retinal thickness cutoffs between 230 and 300 mu m were adopted to define abnormal OCT results and considered the central type of CSME only, whereas in one study a complex algorithm accounting for extrafoveal CSME was used. The design of one study was case-control and was excluded from the meta-analysis. The expected operating point on the summary ROC, a pooled estimate of all studies, corresponded to a sensitivity of 0.79 ( 95% CI: 0.71 - 0.86), a specificity of 0.88 ( 95% CI: 0.80 - 0.93), a positive likelihood ratio of 6.5 ( 95% CI: 4.0 - 10.7), and a negative likelihood ratio of 0.24 ( 95% CI: 0.17 - 0.32). These values suggest a good overall performance of OCT for diagnosing CSME. CONCLUSIONS. OCT performs well compared with fundus stereophotography or biomicroscopy to diagnose diabetic macular edema. The quality of reporting of such studies should be improved, and authors should present cross tabulations of index and reference test results. Data adjusted for within-subject correlation should also be provided, although this issue represents a challenge for systematic reviewers
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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