1,720,991 research outputs found
Antiangiogenic therapy with anti-vascular endothelial growth factor modalities for diabetic macular oedema
No full textBackground Diabetic macular oedema (DMO) is a common complication of diabetic retinopathy. The retina at the macula thickens and this can cause gradual loss of central vision. Although grid or focal laser photocoagulation has been shown to reduce the risk of visual loss in DMO or clinically significant macular oedema (CSMO), vision is rarely improved. Antiangiogenic therapy with anti-vascular endothelial growth factor (anti-VEGF) modalities has recently been proposed for improving vision in people with DMO. Anti-VEGF drugs are delivered by an injection in the vitreous cavity of the eye. Objectives This review aims to assess the effectiveness of anti-VEGF therapy for preserving or improving vision in people with DMO. Search strategy We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE and Caribbean Literature on Health Sciences (LILACS). There were no language or date restrictions in the search for trials. The electronic databases were last searched on 16 April 2009. Selection criteria We included randomised controlled trials (RCTs) comparing any antiangiogenic drugs with an anti-VEGF mechanism of action compared to another treatment, sham treatment, or no treatment. Data collection and analysis Two authors independently extracted the data. The risk ratio (RR) of visual loss and visual gain of 3 or more lines was estimated at least six months after treatment. Main results We found four small studies that collected only short-term outcomes (24 to 36 weeks); three of which had more than two randomisation groups generating five types of comparisons overall. Only one comparison included more than one trial in the analysis. The short-term outcome was the mean change in LogMAR visual acuity. One study on 172 patients compared three doses of pegaptanib versus sham (about 5 injections on average) and another compared bevacizumab or bevacizumab plus triamcinolone with sham (multiple bevacizumab injections and a single triamcinolone injection in 101 patients, 115 eyes overall) in patients with CSMO that was refractory to photocoagulation. Bevacizumab or bevacizumab plus triamcinolone were also compared to photocoagulation in 129 patients with untreated CSMO(150 eyes, multiple injections needed in 24 patients). Although comparisons tended to favour antiangiogenic therapy, estimates did not reach statistical significance or, if they did, they were not robust to sensitivity analysis regarding missing data and potential bias related to single trial estimates. No difference could be demonstrated in one study on 26 patients comparing bevacizumab to triamcinolone (both administered with a single injection) and between bevacizumab and bevacizumab plus triamcinolone in two studies on 182 patients. All the studies in this review, except for the study on pegaptanib, were at risk of bias based on the assessment of six methodological quality items. There were no serious adverse effects in these short-term studies, except for one case of severe anterior uveitis in one eye treated with bevacizumab. No included study examined long-term adverse effects of antiangiogenic therapy. Authors' conclusions There is not sufficient high quality evidence from large RCTs supporting the use of either single or multiple anti-VEGF intravitreal injections to treat DMO. Results from ongoing studies on several compounds should assess not only treatment efficacy but also, if a benefit is found, the number of injections needed for maintenance and long-term safety
Transparent selective contacts for silicon-based heterojunction solar cells
Full text linkRenewable energies are nowadays recognised to be the protagonists of a necessary sustainable transition in the energy production process. Among the existing technologies, photovoltaic (PV) stands out for the infinite availability of the source, the direct efficient energy transformation and for low global energy costs. These reasons drive the global research toward materials and methods to obtain higher and higher efficiencies.
Beyond the well-assessed silicon-based homojunction technology, that covers the 95% of the total PV production, the amorphous/crystalline-silicon heterojunction concept is gaining increasing market share. Heterojunctions (HJs) are able to overcome some shortcomings of homojunctions, such as the high thermal budget connected to the diffusion process to achieve the doping and to the recombination losses that limit the VOC. However HJs still require complex architectures and the use of toxic and dangerous gases, which demand costly measures for a safe industrial manufacturing. A new approach to circumvent some of the above-mentioned issues is currently explored with increasing interest, and involves the use of non-doped, non-silicon films to replace the amorphous-silicon ones. A great variety of materials has already been proposed and tested for the purpose, but some challenges still have to be completely solved, first of all the resistance to thermal annealing at 200-250°C, that is a necessary step in module assembling. Moreover, in view of an industrial application, the manufacture of these novel materials needs to satisfy several constrains and then guarantee an easy and high-throughput process.
In this thesis the attention is focused on some of these novel materials for both emitter and base contacts of a heterostructure solar cell based on n-type doped crystalline silicon. In particular nickel oxide and titanium oxide or zinc sulphide are exploited as selective emitter and base contact respectively. These materials have to be more transparent than the doped amorphous layer counterpart to enhance the quantum yield of the solar cell in the blue region of the solar spectrum where the amorphous films introduce parasitic absorptions. Moreover the substitute layers must be deposited on the well-assessed thin buffer layer of amorphous silicon suboxide used in our laboratory to passivate the surfaces of the silicon wafer, therefore the most relevant constrain to fulfil is to avoid any contamination and any detrimental thermal stress of the surface passivation. On the basis of these requirements, particular care will be given to the choice of the deposition procedures as well as to the choice of the doping elements to be introduced into the selective contacts. The measurement of silicon surface passivation will be adopted as the most relevant method to evaluate the suitability of materials and manufacturing methods. Numerical simulations will also be used to evaluate the ideal band diagram of the proposed heterostructures and to verify how differences in the experimental properties of the materials with respect to ideality could affect the heterostructure device performances.
In analogy with the doped amorphous layers used in conventional HJs, also the proposed novel materials for selective contacts need to be coupled to a transparent conductive oxide to make up for the poor lateral conductivity that still remains a basic issue of any selective layer proposed in the literature up to now. In this thesis another promising material is tested as an alternative to indium tin oxide, namely tungsten-doped indium oxide. It is found that non-reactive radio-frequency sputtering is suited to grow transparent films with very high mobility and low resistivity due a low carrier concentration that reduces parasitic absorptions. Most importantly, the sputtering damage to surface passivation of the crystalline silicon substrates can be completely recovered after a suitable thermal annealing.
All the discussed results show that ideal materials or totally qualified deposition methods for obtaining alternative selective contacts have yet to be found, mostly from the point of view of the resistance to thermal treatments. This thesis adds some tiles to the road to high-efficiency, low-thermal budget, low-toxicity, high-throughput silicon-based heterojunctions
Effects of VEGF inhibition on retinal morphology, neovascular network size, and visual acuity in patients with vascularized pigment epithelium detachment because of occult choroidal neovascularization.
No full textA systematic review of endophthalmitis after microincisional versus 20-gauge vitrectomy.
No full textDiabetic macular edema: classification, medical and laser therapy
No full textPurpose. to propose and describe a new classification of diabetic macular edema (DME) based on its etiopathogenetic features and to present efficacy and safety data on medical and laser treatments currently used and under investigation. Methods. available literature on DME has been reviewed and information provided by contact lens biomicroscopy, fluorescein angiography and optical coherence tomomography has been combined; published data from trials and reports investigating effectiveness of medical and laser treatments were also analyzed. Results. DME was classified according to its main etiopathogenetic components: prevalently retinovascular, tractional and with taut attached posterior hyaloid, each of them having peculiar aspects on fundus, angiographic and tomographic examination. Focal laser treatment remains the only effective intervention, as shown by a large randomized controlled trial, but new less-invasive photocoagulation strategies (i.e., light laser photocoagulation and subthreshold micropulse diode laser) as well as pharmacological approaches (i.e., antioxidants, PKC inhibitors, aldose-reductase and AGE inhibitors, VEGF inhibitors, intravitreal triamcinolone) are emerging. Conclusions. based on our review a classification of DME was developed that may prove useful in making the appropriate treatment decision; the new laser and pharmacological treatments currently investigated are promising and need to be confirmed by large, controlled clinical trials
Bilateral Simultaneous Nonarteritic Anterior Ischemic Optic Neuropathy after Ingestion of Sildenafil for Erectile Dysfunction
Full text linkPurpose. To describe a patient who developed bilateral, simultaneous nonarteritic anterior ischemic optic neuropathy (NAION) after ingestion of Sildenafil citrate (Viagra) for erectile dysfunction. Methods. Observational case report. Results. A 60-year-old diabetic man noted sudden decrease of vision in both eyes 16 hours after his third consecutive 50 mg daily Sildenafil ingestion. A diagnosis of bilateral NAION was made and he was treated for three days with methylprednisolone 1 g/d intravenously, followed by oral prednisone 75 mg/d. Final visual acuity was 20/50 right eye (OD) and 20/20 left eye (OS). He had preexisting diabetes. Conclusion. This is the first reported case of simultaneous bilateral NAION occurred in a diabetic patient early after Sildenafil intake. Patients with predisposing conditions such as diabetes have to be warned against the use of PDE inhibitors
Intravitreal bevacizumab versus ranibizumab for the treatment of retinal angiomatous proliferation
No full textPurpose: To evaluate the effects of intravitreal bevacizumab and ranibizumab treatments in retinal angiomatous proliferation (RAP). Methods: Fifty patients affected by RAP were randomly assigned either to intravitreal bevacizumab injection (IVBI) or intravitreal ranibizumab injection (IVRI). After a loading phase including three consecutive monthly injections, the retreatment was administered in cases of persistent RAP. The primary outcome measures were the mean changes in BCVA between the two treatment groups, and the proportion of eyes gaining 1 and 3 lines at the end of the follow-up. Secondary outcomes included central macular thickness (CMT) changes and progression to more advanced stages of RAP. Results: Fifty patients affected by stage 1 and 2 RAP were recruited. Twenty-six and 24 patients received IVBI and IVRI, respectively. At the baseline, mean best corrected visual acuity (BCVA) values were 0.59 ± 0.21 (LogMAR ± SD, approximately corresponding to 20/80 Snellen Equivalent-SE) in IVBI group and 0.66 ± 0.33 (approximately 20/90 SE) in IVRI group with no statistical difference. At 12-month examination, both groups showed a statistically significant improvement in the BCVA, with a final mean value of 0.43 ± 0.24 (approximately 20/54 SE) in IVBI group and 0.50 ± 0.32 (approximately 20/63 SE) in the IVRI group. A BCVA gain of 1 and 3 lines was registered in 20 and 8 eyes, respectively, in the IVBI group. Similarly, 17 and 7 eyes showed an improvement of 1 or 3 lines, respectively, in the IVRI group. The CMT reduced significantly from baseline to 12-month examination in both groups. A lower proportion of eyes with complete pigment epithelium detachment resolution was noted in the IVBI group than in the IVRI group (40% versus 90%). Conclusions: Our study shows that both IVBI and IVRI are equally effective in improving the BCVA over a 1-year follow-up in eyes affected by stage 1 and 2 RAP
Optimal thermal annealing of a-SiOx layer obtained by pecvd for heterojunction solar cell application
No full textIn a-Si:H/c-Si heterojunction solar cells the UV absorption of amorphous layers limits the current generation. The use of a more transparent material like a-SiOx:H films is a key to further enhance the efficiency of this kind of cells. At the same time this layer must guarantee high surface passivation of the c-Si wafer to be suitable in high efficiency solar cell manufacturing. As for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In order to avoid damages of the amorphous layer, each cell fabrication step should be carried at temperature lower than the emitter formation one. However, when thermal annealing is applied as one of the early fabrication step, the temperature can be high enough to obtain the best passivation properties. In this work we have analyzed the effect of several thermal treatments different for temperature, duration and surrounding atmosphere on a-SiOx:H/c-Si/a-SiOx:H structure. We have fully characterized the samples with the aid of effective lifetime evaluation and FTIR spectra to correlate the effect of thermal annealing to the a-SiOx:H/c-Si interface
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