1,720,978 research outputs found
Preloaded Tissues for Descemet Membrane Endothelial Keratoplasty
No full textIntroduction To determine the feasibility of preloading endothelial tissues for Descemet membrane endothelial keratoplasty (DMEK). Design Laboratory investigation. Methods setting: Institutional. participants: Twenty human donor corneas unsuitable for transplantation with endothelial cell density in a range of 1600-2700 cells/mm2. Intervention: The endothelium was punched, stripped (8.5 mm diameter) and manually tri-folded with the endothelial side inward. The excised membranes were gently moved in a 2.2 intraocular lens (IOL) cartridge and pulled further in the funnel using 25 G end-grasping forceps. The cartridge was filled with transport media (TM) (sealed at its funnel and back entrance with a stopper) and the tissue was preserved for 4 days at room temperature in the bottles containing TM. main outcome measures: Success rate of preparation, processing time, endothelial cell loss (ECL), and active metabolism. Results The tissues were peeled and loaded successfully in all cases. Average stripping and loading time was 20 and 4.5 minutes, respectively. ECL after preservation was 4.35% with 3.55% (± 5.89%) mortality and 7.80% (± 14.12%) uncovered areas. A total of 0.55 (± 0.26) mg/mL of glucose was consumed by the cells showing active metabolism. Conclusions Tri-folded (endothelium-in) DMEK grafts can be preloaded using TM in an IOL cartridge and stored up to 4 days with limited endothelial damage. Direct injection of TM should be avoided because of the presence of bovine serum, but the tissue can be washed using balanced salt solution and gently injected. Alternatively, the graft can be easily delivered using a bimanual pull-through technique. Preloading DMEK grafts will simplify the surgery with reproducibility, reduced surgical time, and reduced tissue wastage, cost, and logistical requirements
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
Descemet membrane endothelial keratoplasty tissue preparation from donor corneas using a standardized submerged hydro-separation method
No full textPurpose To standardize a novel submerged hydro-separation technique for Descemet membrane endothelial keratoplasty (DMEK) graft preparation from donor corneal tissues. Design Experimental study, laboratory investigation. Methods setting: The Veneto Eye Bank Foundation, Venice, Italy. study population: Fifty-four random human donor corneal tissues unsuitable for transplantation. intervention: Donor corneas were laid in a sterile basin partially filled with tissue culture medium. A 25 gauge needle with 1 mL mounted syringe was filled with the tissue culture medium. The needle (with bevel up) was bent to 90 degrees and was inserted in the posterior cornea initiating beneath the trabecular meshwork. It was further advanced toward the midperiphery, ensuring that only the bevel was inserted, considering it as a threshold of insertion. The liquid was injected with a medium to high pressure into the posterior stroma or in the Descemet membrane-stroma interface to create the bubble. The tissues were preserved for 7 days in tissue culture medium at 31°C. Parametrical, physiological and histological analyses were carried out. main outcome measures: Larger-diameter tissue, no tissue wastage, reproducibility, and preshipment evaluation. Results Complete detachment was achieved in all the cases without any tissue wastage. Average diameter of the excised graft was 10.80 (±0.28) mm and endothelial cell loss post preservation was 11.48%. Expression of tight junction protein and regular morphology was observed post preservation. No signs of cell apoptosis were seen. Histological analysis showed elimination of residual stroma in most of the cases. Conclusions The submerged hydro-separation method reduces tissue wastage. It allows preshipment evaluation, thus allowing a validated tissue to be transported from the eye banks to the surgeon. Because of the liquid interface, the peeling of the DMEK graft becomes easy for transplantation. © 2014 by Elsevier Inc. All rights reserved
Banking of donor tissues for descemet stripping automated endothelial keratoplasty
No full textPURPOSE: The demands for precut lamellar grafts for Descemet stripping automated endothelial keratoplasty rose in our eye bank from 74 in 2007 to 408 in 2010. To meet this expanding requirement, we explored the possibility to preserve these preparations in organ culture. METHODS: Organ cultured corneas, stored in a medium containing 6% dextran, were mounted on a Moria artificial anterior chamber, deprived of the epithelium and then cut with a microkeratome. The posterior lamella was protected by positioning the anterior stromal cap, trephined at a diameter of 8.5 mm and stored at 31°C in the medium containing dextran. The endothelium was examined with trypan blue and alizarin staining and tested for its glycolytic activity (conversion of glucose into lactate). RESULTS: Incubation for a period of 1 week caused a small increase in the cell loss observed after trephination (from 6.2% to 10.6%). After 2 weeks, the decrease in endothelial cell density was 19.9% but the endothelial organization remained intact. The rate of glycolysis remained unchanged during the 2 weeks of preservation, with the majority of glucose uptake accounted for by lactate production. The thickness of the lenticules remained constant, ranging from 170 to 180 Î1⁄4m during the preservation. CONCLUSIONS: The lamellar grafts for Descemet stripping automated endothelial keratoplasty may be stored in organ culture for 2 weeks without damaging the endothelium or increasing the overall thickness. Copyright © 2012 by Lippincott Williams & Wilkins
Clinical Outcomes of Preloaded Descemet Membrane Endothelial Keratoplasty Grafts With Endothelium Tri-Folded Inwards
No full textPurpose: To evaluate the initial outcomes and complications of Descemet membrane endothelial keratoplasty (DMEK) using donor tissues tri-folded with the endothelium inwards, preloaded at the Eye Bank, and delivered with bimanual pull-through technique. Design: Prospective, noncomparative, interventional case series. Methods: SETTING: Eye bank and tertiary care eye department. PATIENT POPULATION: Forty-six consecutive eyes of 41 patients with Fuchs endothelial dystrophy with or without cataract operated between November 2016 and March 2017. INTERVENTION: DMEK tissues prepared with SCUBA technique and punched to a diameter of 8.25 mm were preloaded with the endothelium tri-folded inwards in an intraocular lens (IOL) cartridge with a 2.2-mm opening filled with the same tissue culture medium contained in the vial used for shipment to the surgeon. Standardized DMEK was performed as a single procedure (n = 15) or in combination with phacoemulsification and IOL implantation (n = 31) within 48 hours from preparation using a bimanual pull-through technique. MAIN OUTCOME MEASURES: Preparation and surgical times, intraoperative and postoperative complications, best spectacle-corrected visual acuity (BSCVA), endothelial cell density (ECD), and graft detachment rate. Results: Preparation time averaged 26.2 ± 4.1 minutes (range 17–36 minutes), while the surgical time from opening of the stoppers to air fill of the anterior chamber never exceeded 9 minutes (range 3–9 minutes). Surgery was uneventful in all cases. Postoperative complications included graft detachment in 9 of 46 cases (19.6%), successfully managed in all cases by single rebubbling within 6 days from surgery, and glaucoma irresponsive to conservative treatment in 1 of 46 cases (2.1%). In all eyes without comorbidities (35 of 40 eyes) BSCVA was 20/25 (0.097 logMAR) or better as early as 3 months after surgery. Six months postoperatively, ECD was available in 24 of 25 eyes with an endothelial cell loss calculated as a percentage of the preoperative value determined at the eye bank (ranging from 2500 to 2800 cells/mm2) of 29.5% ± 14.8% (range 8.3%–52.1%). Conclusions: Delivering a preloaded DMEK tissue, tri-folded with the endothelium inwards, minimizes surgical time and costs without negatively affecting the outcomes of the procedure
Preloaded donor corneal lenticules in a new validated 3D printed smart storage glide for Descemet stripping automated endothelial keratoplasty
No full textPurpose: To design and validate the efficacy of threedimensional (3D) printed smart storage glide (SSG) which is capable of preserving and delivering posterior lenticules for Descemet stripping automated endothelial keratoplasty (DSAEK). Methods: Laboratory investigation (A) was followed by clinical validation (B). Unsuitable corneas for transplantation (n=20) were used for study A. These tissues were cut using a standard microkeratome, punched and loaded into the SSG and preserved for 7 days in transport media. Endothelial cell density (ECD), Trypan blue and Alizarin red staining for endothelial morphology, thickness measurements and glucose uptake, cell apoptosis and immunostaining post preservation were analysed. For study B, clinical grade corneas (n=14) were preloaded in SSG and grafted in patients with indications of Fuchs' dystrophy (n=8), pseudophakic bullous keratopathy (n=3), posterior polymorphous dystrophy (n=2), and previous DSAEK failure (n=1). Standard DSAEK included descemetorhexis under air and bimanual delivery of the tissue under infusion of buffered saline solution through an anterior chamber maintainer placed at the 12 o'clock position. Main outcome measures for study B were less surgical time, best spectacle-corrected visual acuity (BSCVA), speed of visual recovery, and ECD. Results: For study A, an average ECD loss was 2.30 ±3.21%, thickness increased by 30.80±20.85% and one-third of glucose was utilised during the preservation phase. Alizarin red showed hexagonality of the cells. Cell apoptosis was not observed and expression of ZO-1 was noted on the preserved tissues. In study B, 25% ECD loss was observed after 6 months. BSCVA improved to 20/25 or better within 3 months after DSAEK. Mean surgical time recorded was 21 min. Conclusions: This paper describes the development, design, laboratory and clinical validation of a 3D printed SSG which helps to store and deliver posterior lenticules, therefore allowing transportation of quality-controlled precut tissues
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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