Acute visual loss and intraocular hemorrhages associated with endoscopic spinal surgery

Marilita M Moschos, Alexandros Rouvas, Alexios Papaspirou, Michael ApostolopoulosDepartment of Ophthalmology, University of Athens, GreecePurpose: To report a case of acute visual loss after endoscopic spinal surgery.Methods: A patient was immediately referred to our department after epidural endoscopy with severe bilateral visual impairment and underwent complete ophthalmologic examination.Results: Visual acuity was decreased in both eyes. Fundus examination revealed the presence of retinal and vitreous hemorrhages bilaterally. Four months later, visual acuity increased and the hemorrhages were remarkably resolved.Conclusion: The present case represents an extremely rare incidence of intraocular hemorrhage following epiduroscopy.Keywords: visual acuity, hemorrhage, intraocular, BCV

Photodynamic therapy of choroidal neovascularization with enlargement of the spot size to include the feeding complex

This is a case report of a 83-year-old man with choroidal neovascularization (CNV), due to age-related macular degeneration (AMD) in his right eye. Digital fluorescein (FA) and indocyanine green angiography (ICG) were performed, which disclosed predominantly classic subfoveal CNV and a dilated and tortuous feeding complex. The visual acuity was 20/800. Anti-vascular endothelial growth factor (anti-VEGF) treatment was suggested, however, the patient was not keen to receive an intraocular injection. Modified photodynamic therapy (PDT) with spot size enlarged, to include not only the CNV lesion but the feeding complex as well, was performed. Ten days after one session of PDT, ICG showed absence of leakage from the CNV and complete occlusion of the feeding complex. The visual acuity gradually improved to 20/100 and remained stable during the following 23 months. No evidence of CNV leakage was seen in the FA and ICG during the follow up period. Adjustment of the PDT spot size to include the detectable by ICG feeding complex might be an additional option in order to close the subfoveal CNV and might be considered as an alternative to intravitreal injection of anti-VEGF in selected cases where anti-VEGF treatment is not available

Quantitative determination of glycosaminoglycans in tears of diabetic patients

Marilita M Moschos1, Alexandros A Rouvas1, Spyridon Papadimitriou1, Athanasios Kotsolis1, Nikolaos Sitaras2, Michael Apostolopoulos11Department of Ophthalmology; 2Department of Pharmacology, University of Athens, GreecePurpose: To determine the amount of glycosaminoglycans (GAGs) in tears of patients with diabetic retinopathy (DR) and to compare it with normal subjects.Methods: 38 patients with DR and 24 normal volunteers were included. Thirty subjects suffered from background diabetic retinopathy (BDR) and 8 from proliferate diabetic retinopathy (PDR). For the GAGs assay, the uronic carbazole reaction was used.Results: The mean concentration of GAGs was significantly higher in patients with DR than in normal subjects. The GAGs concentration in patients with BDR or PDR was significantly higher than in normal subjects.Conclusion: The measurement of GAGs in tears of diabetic patients could be a tool in order to assess the stability or not of the disease.Keywords: glycosaminoglycans, tears, diabetic retinopath

EFFICACY OF INTRAVITREAL AFLIBERCEPT IN MACULAR TELANGIECTASIA TYPE 1 IS LINKED TO THE OCULAR ANGIOGENIC PROFILE.

To evaluate intravitreal aflibercept in macular telangiectasia Type 1 (MacTel 1) patients and measure their ocular angiogenic profile. Eight subjects with MacTel 1 refractory to bevacizumab, ranibizumab, or laser therapy and switched to aflibercept were included. Best-corrected visual acuity, central macular thickness, and cystic areas quantified on optical coherence tomography B-scans were assessed during 12 months. Perifoveal capillary densities were measured on optical coherence tomography angiography. Aqueous humor was sampled from six patients and eight control subjects undergoing cataract extraction. Growth factors were quantified using a multiarray immunoassay. Over 12 months, patients received 6.6 ± 1.4 (range, 5-8) intravitreal aflibercept injections. Twelve months after switching to aflibercept, best-corrected visual acuity increased by ≥5 letters in 5 of 8 patients, compared with preaflibercept levels. Mean best-corrected visual acuity improved from 79.6 (∼20/50) to 88.0 (∼20/35) Early Treatment Diabetic Retinopathy Study letters (P = 0.042), and central macular thickness decreased from 434 ± 98 μm to 293 ± 59 μm (P = 0.014). Compared with control subjects, the profile of angiogenic factors in MacTel 1 eyes revealed no difference in vascular endothelial growth factor-A levels but significantly higher levels of placental growth factor (P = 0.029), soluble vascular endothelial growth factor receptor-1 (sFlt-1; P = 0.013), vascular endothelial growth factor-D (P = 0.050), and Tie-2 (P = 0.019). Placental growth factor levels inversely correlated with both superficial and deep capillary plexus densities on optical coherence tomography angiography (P = 0.03). The clinical response to aflibercept coupled to the angiogenic profile of MacTel 1 eyes support the implication of the placental growth factor/Flt-1 pathway in MacTel 1

What Is Stochastic Resonance? Definitions, Misconceptions, Debates, and Its Relevance to Biology

Stochastic resonance is said to be observed when increases in levels of unpredictable fluctuations—e.g., random noise—cause an increase in a metric of the quality of signal transmission or detection performance, rather than a decrease. This counterintuitive effect relies on system nonlinearities and on some parameter ranges being “suboptimal”. Stochastic resonance has been observed, quantified, and described in a plethora of physical and biological systems, including neurons. Being a topic of widespread multidisciplinary interest, the definition of stochastic resonance has evolved significantly over the last decade or so, leading to a number of debates, misunderstandings, and controversies. Perhaps the most important debate is whether the brain has evolved to utilize random noise in vivo, as part of the “neural code”. Surprisingly, this debate has been for the most part ignored by neuroscientists, despite much indirect evidence of a positive role for noise in the brain. We explore some of the reasons for this and argue why it would be more surprising if the brain did not exploit randomness provided by noise—via stochastic resonance or otherwise—than if it did. We also challenge neuroscientists and biologists, both computational and experimental, to embrace a very broad definition of stochastic resonance in terms of signal-processing “noise benefits”, and to devise experiments aimed at verifying that random variability can play a functional role in the brain, nervous system, or other areas of biology

Theoretical methods to predict the interaction of aero-engine fan tone radiation with the fuselage and its boundary layer

The work in this thesis is focused on the acoustic installation effects of an aero-engine fan noise source adjacent to a cylindrical fuselage with a boundary layer running down its length. The main scope of this work is the development of theoretical methods to quantify scattering/diffraction by the fuselage and the refraction effect due to the presence of the boundary layer. The aim is to provide a faster and less computationally demanding alternative to high-fidelity numerical methods. The acoustic near-field of an installed fan noise source hasbeen investigated before with the use of numerical methods to solve the problem of sound propagation through the shear layer. Therefore, in this work analytic expressions are derived that describe the acoustic pressure both in the near-field, in the form of a Fourier series and aFourier integral, and in the far-field, in the form of a Fourier series. The use of numerical methods is avoided by utilising an asymptotic method for thin linear boundary-layer profiles. Additionally, a rudimentary step-function profile is investigated that avoids the solution to the Pridmore-Brown equation altogether. The capability of the two profiles to approximate the effects of more complex boundary layer profiles such as the quarter-sine and the 1/7th power-law profile is investigated. The analytic expressions are validated by comparing theoretical results to existing numerical results for the pressure on the fuselage surface. Thetwo equivalent simplified profiles prove to be able to approximate the same effects as more realistic profiles especially for thin boundary layers. The linear profile accurately predicts shielding effects for thin boundary layers, but the step-function profile retains its accuracy regardless of the boundary-layer thickness. Both theoretical approaches are able to capture the pressure contour pattern and amplitude of shielding on the fuselage surface. The main advantage of this novel theoretical approach is the speed at which it can produce reliable results since there is no need for numerical schemes. Therefore, a multi-mode parametric study is conducted that identifies shielding trends on the fuselage surface and far-field directivity trends in various stages of flight. Multiple flow and source characteristics are examined with flight Mach number, cut-off ratio of the modal output of the fan, and boundary-layer thickness standing out as the major factors that affect shielding on the fuselage surface and directivity phase shifts in the far-field. The results of the multi-mode parameteric study highlight the capability of this novel theoretical approach to produce quick and reliable results that can serve as a preliminary analysis to a more in-depth numerical analysis