1,721,038 research outputs found
Surgical management of retinal detachment because of macular hole in highly myopic eyes
No full textPURPOSE: The purpose of this study was to review the current management of macular hole retinal detachment in highly myopic eyes. METHODS: We searched English MEDLINE databases from January 1997 to January 2011 for surgical management of macular hole retinal detachment in highly myopic eyes. The main outcomes reported include retinal reattachment and visual acuity after primary surgery. RESULTS: Surgical procedures including pneumoretinopexy, pars plana vitrectomy with gas or silicone oil tamponade with or without laser therapy around the macular hole, and macular buckling have been the primary treatment choices. New techniques, including internal limiting membrane or epiretinal membrane peeling and heavy silicone oil tamponade, have been introduced over the last decade, and use of optical coherence tomography has allowed evaluation of the postoperative anatomical status of holes undetectable by conventional ophthalmoscope or lens biomicroscope. Poor functional and anatomical outcomes and nonclosure or reopening of a macular hole are still crucial problems, and some patients may require multiple procedures. CONCLUSION: Macular hole retinal detachment in highly myopic eyes is one of the most difficult types of retinal detachment to treat, and its primary treatment choice is still controversial, although the different surgical techniques reported in this review have been demonstrated as good surgical options. Randomized clinical trials are largely lacking. © Lippincott Williams & Wilkins
Transconjunctival sutureless 25-gauge versus 20-gauge standard vitrectomy: Correlation between corneal topography and ultrasound biomicroscopy measurements of sclerotomy sites
No full textPurpose: To determine the correlation between corneal shape changes and ultrasound biomicroscopy (UBM) findings at the sclerotomy sites in conventional 20-gauge (G) pars plana vitrectomy (PPV) and 25-G transconjunctival sutureless vitrectomy (TSV) and to compare the effectiveness of the two surgical methods. Design: Prospective, comparative, observational case series. Methods: Sixty consecutive eyes (60 patients) undergoing primary 3-port PPV. Thirty eyes (30 patients, group 20-G) were treated with 20-G standard PPV and 30 eyes (30 patients, group 25-G) with 25-G TSV. We compared healing of the sclerotomy sites in the two groups. We determined the correlation between corneal shape changes (surgically induced astigmatism) measured by videokeratography and the durations of scleral healing cicatrization by UBM within each group. Results: UBM examination showed that the 20-G sclerotomy sites took about 8 weeks to heal, measured as complete opposition, whereas healing of the 25-G TSV sclerotomy was quite rapid, with complete scleral opposition in about 4 weeks. Corneal topography analysis showed, during the early postoperative period, a surgically induced steepening of the cornea in both groups (20 G, 3.08 ± 0.56 diopters and 25 G, 0.805 ± 0.61 diopters, P < 0.001, Mann-Whitney test), which then decreased gradually, recovering to the preoperative level within two months in group 20 G (P > 0.05) and 1 month in group 25 G (P > 0.05). We found a strong statistical correlation between the mean surgically induced keratometric astigmatism and the mean UBM measures of scleral healing (r = 0.99 for group 20 G and r = 0.97 for group 25 G). Conclusion: After PPV, astigmatic changes are especially significant in the early postoperative period in 20-G group; the 25-G TSV system results in faster reduction of surgically induced keratometric astigmatism because of rapid cicatrization of the sclerotomy sites. © 2009 by Lippincott Williams & Wilkins
Sensitivity-based investigation of threshold voltage variability in 32-nm flash memory cells
Full text linkWe investigate variability of a 32 nm flash memory cell and of 32 nm MOSFETs with a methodology based on sensitivity analysis performed with a limited number of TCAD simulations. We show that – as far as the standard deviation of the threshold voltage is concerned – our method provides results in very good agreement with those from three-dimensional atomistic statistical simulations, with a computational burden that is orders of magnitude smaller. We show that the proposed approach is a powerful tool to understand the role of the main variability sources and to explore the device design parameter space
Possible involvement of nitric oxide in morphine-induced miosis and reduction of intraocular pressure in rabbits.
No full textThe role of μ3 opioid receptors in morphine-induced intraocular pressure (IOP) lowering effect and miosis was evaluated in conscious, dark-adapted New Zealand white (NZW) rabbits using a masked-design study. IOP and pupil diameter (PD) measurements were taken at just before and 0.5, 1, 2, 4, 6 h after monolateral instillation of morphine (10, 50 and 100 μg/30 μl) as compared to vehicle administered in the contralateral eye. Morphine-induced ocular effects were challenged by a pre-treatment with the non-selective opioid receptor antagonist, naloxone (100 μg/30 μl), the nitric oxide synthase inhibitor, Nω-nitro-l-arginine methyl ester (l-NAME, 1%, 30 μl), or the non-selective μ3 opioid receptor inhibitor, reduced l-glutathione (GSH, 1%, 30 μl). Morphine induced a dose-dependent decrease in IOP and PD. Pre-treatment with naloxone totally prevented morphine-induced decrease in IOP and miosis. Ocular administration of l-NAME or GSH alone failed to affect IOP or PD of NZW rabbits. However, pre-treatment with either drugs significantly reduced, but not totally prevented ocular effects of morphine. These results suggest that biochemical mechanisms related to nitric oxide release are involved, at least in part, in morphine effects on the eye. Since the μ3 opioid receptor subtype is able to release nitric oxide and is sensitive to inactivation by GSH, it may be possible that μ3 opioid receptors are involved in morphine-induced miosis and reduction in IOP. © 2006 Elsevier B.V. All rights reserved
Correlation of optical coherence tomography pattern and visual recovery after vitrectomy with silicone oil for retinal detachment
No full textPURPOSE: To assess prospectively the features of the macular surface in silicone oil-filled eyes after surgery by analyzing whether silicone oil affects optical coherence tomography (OCT) measurements and their reproducibility and whether a statistical correlation exists between postoperative best-corrected visual acuity (BCVA) and foveal thickness measured by OCT. METHODS: Twenty eyes of 20 patients underwent vitrectomy with silicone oil tamponade for retinal detachment. After vitrectomy, complete ophthalmic examination including determination of BCVA and OCT was performed to quantify the visual recovery and the foveal thickness. RESULTS: Ophthalmoscopy revealed that the retina appeared to be reattached in all 20 eyes at 3 months after surgery. BCVA ranged from 0.4 logMAR to 1.7 logMAR, and foveal thickness ranged from 80 μm to 500 μm. Postoperative foveal thickness and BCVA had a strong correlation (r = 0.93; P = 0.003). CONCLUSION: The presence of silicone oil in the vitreous chamber does not change the reproducibility of OCT measurements of foveal thickness (coefficient of reproducibility, 1.48%). This study showed high statistical correlation between BCVA and foveal thickness. Therefore, postoperative BCVA is affected by postoperative foveal thickness, and visual improvement is limited in eyes with increased or decreased foveal thickness. © The Ophthalmic Communications Society, Inc
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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