861 research outputs found
Optical Coherence Tomography Findings in Rhegmatogenous Retinal Detachment: A Systematic Review
Rhegmatogenous retinal detachment is a sight-threatening condition that may lead to blindness if left untreated. Surgical treatments may vary and are tailored to a single patient. Anatomical and functional results may vary, due to factors that are currently under study. Optical coherence tomography (OCT) allows a detailed visualization of the retinal structure. Some studies have been performed using OCT on eyes with retinal detachment. We performed a review on the subject. Several data have been obtained using different OCT applications. Some alterations may represent potential biomarkers since they are associated with visual and anatomical prognoses. Increased knowledge on the subject may be helpful to choose among different surgical strategies and endotamponades. More research on the topic is needed
The Ultraviolet Luminosity Density of the Universe from Photometric Redshifts of Galaxies in the Hubble Deep Field
Studies of the Hubble Deep Field (HDF) and other deep surveys have revealed
an apparent peak in the ultraviolet (UV) luminosity density, and therefore the
star-formation rate density, of the Universe at redshifts 1<z<2. We use
photometric redshifts of galaxies in the HDF to determine the comoving UV
luminosity density and find that, when errors (in particular, sampling error)
are properly accounted for, a flat distribution is statistically
indistinguishable from a distribution peaked at z~1.5. Furthermore, we examine
the effects of cosmological surface brightness (SB) dimming on these
measurements by applying a uniform SB cut to all galaxy fluxes after correcting
them to redshift z=5. We find that, comparing all galaxies at the same
intrinsic surface brightness sensitivity, the UV luminosity density contributed
by high intrinsic SB regions increases by almost two orders of magnitude from
z~0 to z~5. This suggests that there exists a population of objects with very
high star formation rates at high redshifts that apparently do not exist at low
redshifts. The peak of star formation, then, may occur somewhere beyond a
redshift z~>5.Comment: 4 pages total, including 3 embedded figures, to appear in the
proceedings of the Xth Rencontres de Blois, "The Birth of Galaxies." LaTeX
style file include
The Origin of C IV Absorption Systems at Redshifts z<1---Discovery of Extended C IV Envelopes Around Galaxies
(Abridged) We report the discovery of extended CIV gaseous envelopes around
galaxies of a wide range of luminosity and morphological type. First, we show
that CIV absorption systems are strongly clustered around galaxies on velocity
scales of v < 250 km/s and impact parameter scales of rho < 100 h^{-1} kpc but
not on larger velocity or impact parameter scales. Next, adopting measurements
of galaxy properties presented in previous papers, we examine how properties of
the CIV absorption systems depend on properties of the galaxies. On the basis
of 14 galaxy and absorber pairs and 36 galaxies that do not produce
corresponding CIV absorption lines to within sensitive upper limits, we find
that: (1) Galaxies of a range of morphological type and luminosity appear to
possess extended CIV gaseous envelopes of radius R ~ 100 h^{-1} kpc, with
abrupt boundaries between the CIV absorbing and non-absorbing regions. (2) The
extent of CIV-absorbing gas around galaxies scales with galaxy B-band
luminosity as R \propto L_B^{0.5 +/- 0.1} but does not depend strongly on
galaxy surface brightness, redshift, or morphological type. And (3) the
covering factor of CIV clouds within ~ 100 h^{-1} kpc of galaxies is nearly
unity, but there is a large scatter in the mean number of clouds encountered
along the line of sight. The most significant implication of the study is that
galaxies of a wide range of luminosity and morphological type are surrounded by
chemically enriched gas that extends for at least ~ 100 h^{-1} kpc. We consider
various scenarios that may have produced metals at large galactic distance and
conclude that accreting satellites are most likely to be responsible for
chemically enriched gas at large galactic distances to regular looking
galaxies.Comment: 19 pages, 3 figures, to appear in ApJ, July 20 200
Star-forming galaxies at very high redshifts
Analysis of the deepest available images of the sky, obtained by the Hubble
Space Telescope, reveals a large number of candidate high-redshift galaxies. A
catalogue of 1,683 objects is presented, with estimated redshifts ranging from
to . The high-redshift objects are interpreted as regions of star
formation associated with the progenitors of present-day normal galaxies at
epochs reaching to 95\% of the time to the Big Bang.Comment: 10 pages, LaTeX type, aaspp4.sty macro provided. Supplementary
information, including the full catalog, plots of spectra and redshift
likelihood functions for all the objects, and composite spectra, are
available at ftp://ftp.ess.sunysb.edu/pub/hd
A mini-invasive surgical technique for Carlevale IOL implantation: case series study and description of concomitant surgery
Purpose: To examine the feasibility and outcomes of a modified technique for the implantation of scleral fixated Carlevale intraocular lens (IOL) (I71 FIL SSF. Soleko IOL Division, Pontecorvo, Italy), and to analyze the occurrence of adverse events. Methods: This is a retrospective observational study conducted revising patients charts from 2018 to 2023. Thirty-five eyes of 33 patients were included. Patients requiring IOL explantation had either IOL dislocation or opacification. The implantation of the Carlevale IOL was performed with the subconjunctival positioning of the anchors without any scleral flap. All maneuvers were performed transconjunctivally. The anatomical outcomes considered were IOL positioning, and the absence of postoperative complications. The functional outcomes analyzed were best correctedvisual acuity (BCVA) and refraction. Results: In all the cases, the IOL was well positioned and centered postoperatively. No cases of conjunctival erosion were recorded. The best corrected visual acuity (BCVA) was 0.9±0.6 logMar (mean±standard deviation) preoperatively and 0.5±0.5 logMar (mean±standard deviation) postoperatively. The mean preoperative spherical equivalent was +6.8±7.7 dioptres, while postoperatively it was -1.1±1.6 dioptres. The most frequent procedure associated to secondary IOL implantation was posterior vitrectomy (25 eyes, 71.4%), which was performed with 25-gauge transconjunctival cannulas in the ciliary sulcus. The follow-up period was 24.5±16.9 months (mean±standard deviation). Conclusion: The described mini-invasive technique for Carlevale IOL implantation is safe and effective. It can be recommended either as a stand-alone operation or associated to concurrent surgical procedures
Detailed analysis of an endoreversible fuel cell : Maximum power and optimal operating temperature determination
Producing useful electrical work in consuming chemical energy, the fuel cell
have to reject heat to its surrounding. However, as it occurs for any other
type of engine, this thermal energy cannot be exchanged in an isothermal way in
finite time through finite areas. As it was already done for various types of
systems, we study the fuel cell within the finite time thermodynamics framework
and define an endoreversible fuel cell. Considering different types of heat
transfer laws, we obtain an optimal value of the operating temperature,
corresponding to a maximum produced power. This analysis is a first step of a
thermodynamical approach of design of thermal management devices, taking into
account performances of the whole system.Comment: 15 pages, 10 figure
Managing diabetic macular edema in clinical practice: systematic review and meta-analysis of current strategies and treatment options
Purpose: This meta-analysis aims to summarize 12-month best-corrected visual acuity (BCVA) outcomes in response to anti-vascular endothelial growth factor (VEGF) therapy and dexamethasone implant for the treatment of diabetic macular edema (DME) and to identify factors affecting treatment response using evidence generated from metaregression. Methods: A systematic review of electronic databases was conducted to identify randomized controlled trials (RCTs) and real-life/observational studies that reported 12-month changes in BCVA in patients with DME on anti-VEGF or dexamethasone implant treatment in monotherapy. Study factors that were analyzed are baseline patient characteristics, study type, drug employed, number of injections and 12-month change in BCVA. Data were pooled in a random-effects meta-analysis with BCVA change as the main outcome. Meta-regression was conducted to assess the impact of multiple covariates. Results: One-hundred-five heterogeneous study populations (45,032 eyes) were identified and included in the analysis. The use of anti-VEGFs and dexamethasone implant induced an overall increase of +8.13 ETDRS letters in BCVA at 12 months of follow-up. Metaregression provided evidence that mean BCVA change using anti-VEGFs was not statistically higher for RCTs (p=0.35) compared to observational studies. Dexamethasone implant showed a trend for better results in observational studies over RCTs. Populations following a fixed aflibercept regimen performed better than those following a reactive treatment regimen. Mean BCVA gain was higher in younger populations (p<0.001), with lower baseline BCVA (p<0.0001) and longer diabetes duration (p<0.0001), receiving a higher number of injections (p<0.0001). Conclusion: Intravitreal therapy with anti-VEGFs or dexamethasone implant produces a significant improvement in BCVA at 12 months in patients with DME. Meta-regression identified the modifiable covariates that can be targeted in order to maximize functional results
Infection control measures in ophthalmology during the COVID-19 outbreak: A narrative review from an early experience in Italy
Introduction: The novel coronavirus (SARS-CoV-2) is infecting people and spreading easily from person-to-person. Cases have been detected in most countries worldwide. Italy is one of the most affected countries as of 30 March 2020. Public health response includes a rapid reorganization of the Italian National Healthcare System in order to reduce transmission of COVID-19 within hospitals and healthcare facilities, while optimizing the assistance to patients with severe COVID-19 complications. Methods: We analysed the actions that were taken in three ophthalmology centres in northern Italy during the SARS-CoV-2 outbreak and how these measures affected patient\u2019s attendance. In addition, due to the rapidly evolving scenario, we reviewed the evidence available during the course of this pandemic. Results: A full reorganization of ophthalmology services is mandatory according to current existing infection containment measures in order to continue dispensing urgent procedures without endangering the community with amplification of the diffusion chain. Ophthalmologists are considered at elevated risk of exposure when caring patients and vice versa, due to their close proximity during eye examination. High volumes of procedures typically generated by ophthalmologists with concurrent implications on the risk of infection are considered when re-assessing healthcare facilities reorganization. Conclusion: Containment measures in the event of pandemic due to infective agents should be well known by healthcare professionals and promptly applied in order to mitigate the risk of nosocomial transmission and outbreak
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