1,721,108 research outputs found
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
Vergleich von Monitorstimulation und LED-Stimulation in der multifokalen Elektroretinographie
No full textMannan binding lectin related to CSF and MRI findings in optic neuritis and multiple sclerosis
No full textEntwicklung eines resorbierbaren Vorderkammer-Glaukomimplantates
No full textThe glaucomas are potentially treatable diseases, either by medication or surgery. Ab externo Er:YAG-laser sclerostomy, as an alternative surgical glaucoma therapy, produces a drainage canal from the anterior chamber into subconjunctival space. The procedure by itself did not achieve the desired success, as postoperative scarring of episcleral tissue often resulted in occlusion of the canal. The implant concept introduced in this study modifies the Er:YAG-lasersclerostomy procedure. The aim is to obtain an intact corneoscleral canal during the postoperative inflammatory period by implanting a non-draining stent into the canal as a placeholder. This should make for more favourable conditions for long-term functionality of the drainage canal after explantation of the stent. To avoid the necessary explantation procedure of the silicone stent, biodegradable plastics were tested for applicability as a possible stent-material, as the second part of this study.The silicone implant consists of a 300µm pim which bottoms out into a small flag. After conduction of the laser-sclerostomy the stent was implanted into four chinchilla-rabbits. Six weeks after implantation two animals were enucleated with stent in situ to evaluate the sclerostomy-morphology around the stent as well as subconjunctival reactions to the stent site. Two further animals underwent stent-explantation at the same time, enucleation was conducted 14 weeks after stent explantation. Bulbi were histologically processed. Analysis of the biodegradable glycolid-copolymers and of multiblockcopolymer oligo(p-dioxanon)diol, oligo(alkylen-glykoladipat)diol and diisocyanat (PDA) included processing, degradation in phosphate buffer, degradation in L929-conjunctival fibroblast culture, and biocompatibility testing for multiblockcopolymer PDA, consisting of EB/FDA vital staining, BrDU-, WST-1-elisa and cellmorphologic analysis of L929-fibroblasts.Surgical practicability of stent implantation was documented as well as high acceptance of subconjunctival tissue for the silicone stent. Histology showed fibrocellular connective tissue in the canal with the stent luxated from the canal. A pronounced fibrocellular sheathing was seen around the stent flag. The implant could not be found in one eye. Only minor inflammation was persistent 14 weeks after explantation, with fibrocellular occlusion of the canal. Iris incarceration occured in one eye after stent explantation without further complications.In the course of material analysis the glycolid-polymers turned out to be unemployable for stent construction due to missing elasticity and acidic degradation. Multiblockcopolymer PDA showed comparable results as biofilm-reference for all cytotoxicity testings. The results of degradation analysis were linear degradation without noticeable loss of elasticity and a less pronounced pH-value decrease.Modification of the lasersclerostomy-procedure by stent implantation could serve as a method to ameliorate postoperative conditions for a functioning drainage canal. The surgical procedure is easy to do and requires little complexity. Implantation of the non-degradable implant would be possible, following a concise explantation procedure in local anesthesia. Application and evaluation of the degradable PDA-stent in an animal model would be the next step, thus avoiding the traumatising explantation of the permanent silicone stent. The main aim is to avoid a remaining immunogenic foreign body in subconjunctival space. The labelled aspects should be subjects of further research
Vergleich von Monitorstimulation und LED-Stimulation in der multifokalen Elektroretinographie
No full textAntimikrobielle Therapie der Hornhaut : die Pharmakokinetik in der lokalen Therapie und ihre Optimierung durch den Mikrotrepan; am Beispiel von Ciprofloxacin und PVP-Jod
No full textThe basis to this work is a study which consists of two parts. The first one was done during an Erasmus exchange-program at the Department of Ophthalmology of the University of Trondheim, Norway, the second one at the Department of Ophthalmology of the RWTH Aachen. The starting point of both parts is the comparison of two methods to examine the anterior compartment of the eye. Another parallel in both parts is the analysis of the pharmacocinetics of two different substances in the topical therapy of the cornea. The main focus of each part of the study was different, as described below. Methods: In the first part, we used NMR spectroscopy (nuclear magnetic resonance) to analyse drugs containing fluor and to detect them in the anterior segments of the eye. The antibiotic Ciprofloxacin served as example in this study. In the second part we examined the therapeutical potency of the microtrephine in the corneal therapy. We used Polyvidon-Iodine (PVP-Iodine) as reference substance in relation to Ciprofloxacin in order to study penetration into the cornea. The analysis was performed by energy-dispersive x-ray analysis (EDXA). Topical application of the two different substances was performed in rabbits, following a defined protocol. Afterwards, the tissue of interest (cornea, aqueous humour, lens) was excised and prepared for analysis. Results: Ciprofloxacin is detected by means of 19F NMR spectroscopy in the aqueous humour, cornea and lens of the rabbits following topical application. It is quantified in the cornea. 1H NMR spectroscopy makes it possible to analyse the metabolic state of the examined tissue. We identify about 20 different metabolites in both the aqueous humour and the cornea. EDX-analysis allows the detection of PVP-Iodine in the different layers of the cornea and a differentiated analysis and visualisation of the substance’s penetration into the corneal stroma through intact epithelium or after microtrephination respectively. Discussion: By means of NMR spectroscopy a quantification of substances containing fluor is possible in the different parts of the anterior segment of the eye. The detection of Ciprofloxacin in the lens is described for the first time. EDX-analysis allows a differentiated analysis of the corneal layers concerning the metabolic state and the presence of substances containing iodine. Penetration of topically applied substances into the tissue can be visualised. Ciprofloxacin was not detectable by this method. The concentration of fluor in the cornea after the topical application of Ciprofloxacin following our protocol was too low to be detected by EDX-analysis. We could show, that the treatment with the microtrephine prior to local therapy optimises local penetration of topically applied PVP-Iodine into the corneal stroma and thus may open an improvement of local therapy of the cornea for defined indications
Entwicklung eines Gerätes zur Druckmessung an der Aachener Keratoprothese
No full textPurpose: Postoperative glaucoma is one of the major complications observed in patients with keratoprostheses. The optical components of the majority of KPros are rigid and inflexible, which prevents indirect tonometry with common methods. This study confirms that the Aachen-KPro allows measurements of the intraocular pressure (IOP) due to its flexible optical part with a modified Schiotz tonometer. Methods: The Aachen-KPro was placed in a special chamber where pressure can be generated and monitored by a transducer. Measurements were performed with common ophthalmologic methods. The results were compared to the initial pressure values in the chamber. Results: With the Goldmann tonometer, the Tono-Pen and the topography system (Technomed), no significant pressure changes could be observed. The results of the Schiotz tonometer were promising. It was slightly modified and standard curves with different weights could be obtained. Conclusions: With a modified Schiotz tonometer, it is possible to detect elevated IOPs. Modifying this common instrument is inexpensive and can be performed easily. This advantage of the Aachen-KPro permits early management of postoperative high tension glaucoma
Neue biokompatible De-novo-Synthesen als okuläre Endotamponaden : tierexperimentelle Untersuchungen
No full textDie Anwendung des EVEIT-Tests in der Bewertung von Chemikalien und Medikamenten
No full textWith the objective of replacing the need of living animals to test chemicals respectively their reactions on the eye we created the EVEIT System. Therefore we designed a perfusion chamber in which rabbit corneas of animals that were killed for the food industry were clamped. Their nutrition was guaranteed by a special nutrition medium and the whole setup was stored in a breeder which ensured a constant temperature of 31°C. We did testings in mechanical and chemical ways on these cultivated corneas besides untreated control groups. The corneas were evaluated by morphological (endothelial and epithelial examinations) and biochemical (pH, glucose-lactate-metabolism, cytokines, growth factors in the medium) criteria. We could show that in principle a total healing of the cornea and a recover of the glucose-lactate-metabolism is possible after trauma. Different chemicals presented varying patterns of trauma and wound healing. The testings with different concentrations of the chemicals give at least a hint of dose response. But further testings with bigger groups of treated corneas and other concentrations need to be done to give better statements
- …
