Impact of COVID-19 pandemic on ophthalmic presentations to an Australian outer metropolitan and rural emergency department: a retrospective comparative study.

BACKGROUND: To analyse ophthalmic presentations to an outer metropolitan and a rural emergency department (ED) during the first wave of the COVID-19 pandemic in New South Wales (NSW), Australia. METHODS: A retrospective comparative study of ophthalmic emergency presentations to Campbelltown Hospital (fifth busiest NSW metropolitan ED; population 310,000) and Bowral and District Hospital (rural ED; population 48,000) before and during COVID-19 was conducted. Patient demographics, triage category, referral source, diagnosis, length of stay, departure status, and follow-up location were assessed from coding data between March 1st to May 31st in 2019 and 2020, corresponding to the peak case numbers and restrictions during the first wave of the COVID-19 pandemic in NSW. Differences before and during COVID-19 were analysed using chi-squared tests or independent sample t-tests. RESULTS: There was no change in ophthalmic presentations at Campbelltown (n = 228 in 2019 vs. n = 232 in 2020; + 1.75%, p = 0.12) and an increase at Bowral (n = 100 in 2019 vs. n = 111 in 2020; + 11%, p < 0.01) during COVID-19. Urgent ophthalmic presentations (Triage Category 3) decreased at Bowral (p = 0.0075), while non-urgent ophthalmic presentations (Triage Category 5) increased at both hospitals (Campbelltown p < 0.05, Bowral p < 0.01). CONCLUSIONS: There was no change in the total number of ophthalmic presentations to an outer metropolitan and an increase to a rural ED during the first wave of the COVID-19 pandemic in New South Wales, Australia. A change in the type of ophthalmic presentations at these peripheral EDs suggest that a high demand for ophthalmic services remained despite the pandemic and its associated gathering and movement restrictions. A flexible healthcare delivery strategy, such as tele-ophthalmology, may optimise patient care during and after COVID-19

A combined convolutional and recurrent neural network for enhanced glaucoma detection.

Glaucoma, a leading cause of blindness, is a multifaceted disease with several patho-physiological features manifesting in single fundus images (e.g., optic nerve cupping) as well as fundus videos (e.g., vascular pulsatility index). Current convolutional neural networks (CNNs) developed to detect glaucoma are all based on spatial features embedded in an image. We developed a combined CNN and recurrent neural network (RNN) that not only extracts the spatial features in a fundus image but also the temporal features embedded in a fundus video (i.e., sequential images). A total of 1810 fundus images and 295 fundus videos were used to train a CNN and a combined CNN and Long Short-Term Memory RNN. The combined CNN/RNN model reached an average F-measure of 96.2% in separating glaucoma from healthy eyes. In contrast, the base CNN model reached an average F-measure of only 79.2%. This proof-of-concept study demonstrates that extracting spatial and temporal features from fundus videos using a combined CNN and RNN, can markedly enhance the accuracy of glaucoma detection

Pressure dependency of retinal arterial pulse wave velocity in the rat

© 2020 Association for Research into Arterial Structure and Physiology. Publishing services by Atlantis Press International B.V. This is an open access article distributed under the CC BY-NC 4.0 license (http://creativecommons.org/licenses/by-nc/4.0/). Purpose: The retinal vasculature provides unique in vivo access to the microcirculation and presents the possibility of measuring small artery (retinal) stiffness using pulse wave velocity (PWV). This study investigates whether retinal artery PWV (rPWV) has a blood pressure (BP) dependency. Methods: Fundus videos from eight Sprague-Dawley rats aged 12 weeks were captured (Zeiss fundus microscope with high-speed camera, 125 fps, Optronis, Germany) simultaneously with aortic BP. Retinal artery diameter waveforms at proximal and distal sites were extracted and transit time calculated from the phase delay between frequency components (4–6 Hz, typical heart rate of rats) of the waveforms. rPWV was measured across a physiological range of mean arterial pressure (MAP): baseline (90–110 mmHg); 130 mmHg to baseline following systemic phenylephrine (PE) infusion (30 mg/kg/min); 130 mmHg to baseline during PE infusion with simultaneous inferior vena cava occlusion (VO); 70 mmHg to baseline following systemic sodium nitroprusside infusion; and 70 mmHg to baseline following VO. The correlation between retinal artery rPWV and BP was quantified. Results: There was a significant positive correlation between retinal artery rPWV and MAP as expected (0.19 mm/s/mmHg, R2 = 0.59, p < 0.001). There was a positive correlation between retinal and aortic PWV (R2 = 0.09, p = 0.03). Conclusion: The pressure dependency of the measured rPWV indicates the measure has utility in in vivo quantification of the impact on microvessels of cardiovascular diseases. To elucidate the predictive value of screening rPWV in systemic cardiovascular abnormalities, the relation needs to be investigated in humans

Structural, optical and thermal properties of silver colloidal nanoparticles

In this paper, colloidal silver nanoparticles were prepared by chemical reduction of AgNO3 and pure Sn in a new and simple method. The type of crystallite lattice and the size of nanopowders were estimated by X-Ray Diffraction (XRD) analysis. The geometric, heterogeneous and mixing structure of synthesized nanopowders were studied by Scanning Electron Microscopy (SEM). Optical properties such as plasmon absorption and frequency of soluble colloidal nanopowders in two solutions of distilled water and oil were investigated by UV-Visible spectroscopy, which was developed to calculate the absorbance spectra of nanoparticles solution containing a size distribution of particles using the Mie theory. Dipole and quadrupole plasmons related to molecular structure of water and oil were found by absorbance spectra. Also, Differential Scanning Calorimetry (DSC) analysis was used for determining the thermal behavior, endothermic and exothermic peaks of Ag nanopowder

SSP: Early prediction of sepsis using fully connected LSTM-CNN model.

Background: Sepsis is a life-threatening condition that occurs due to the body's reaction to infections, and it is a leading cause of morbidity and mortality in hospitals. Early prediction of sepsis onset facilitates early interventions that promote the survival of suspected patients. However, reliable and intelligent systems for predicting sepsis are scarce.Methods: This paper presents a novel technique called Smart Sepsis Predictor (SSP) to predict sepsis onset in patients admitted to an intensive care unit (ICU). SSP is a deep neural network architecture that encompasses long short-term memory (LSTM), convolutional, and fully connected layers to achieve early prediction of sepsis. SSP can work in two modes; Mode 1 uses demographic data and vital signs, and Mode 2 uses laboratory test results in addition to demographic data and vital signs. To evaluate SSP, we have used the 2019 PhysioNet/CinC Challenge dataset, which includes the records of 40,366 patients admitted to the ICU.Results: To compare SSP with existing state-of-the-art methods, we have measured the accuracy of the SSP in 4-, 8-, and 12-h prediction windows using publicly available data. Our results show that the SSP performance in Mode 1 and Mode 2 is much higher than existing methods, achieving an area under the receiver operating characteristic curve (AUROC) of 0.89 and 0.92, 0.88 and 0.87, and 0.86 and 0.84 for 4 h, 8 h, and 12 h before sepsis onset, respectively.Conclusions: Using ICU data, sepsis onset can be predicted up to 12 h in advance. Our findings offer an early solution for mitigating the risk of sepsis onset

Measurement of retinal artery pulse wave velocity in the rat using high speed imaging

Background: Arterial stiffness, as measured by arterial pulse wave velocity (PWV) in large conduit arteries, is being increasingly accepted as a significant prognostic index of cardiovascular function. The significance of PWV in arteries in the microvasculature is not yet established, due mainly to the difficulty in obtaining reliable non-invasive measurements in vivo. The eye, as the only organ providing direct non-invasive imaging access to its internal anatomical structure, has the potential to be used to assess arterial stiffness at the level of the microcirculation. Aim: To develop signal processing and high-speed imaging techniques to measure pulse transit time (PTT) to determine retinal artery PWV (rPWV) in the rat eye. Methods: Measurements were performed in nine Wistar-Kyoto (280±30 g, 12 weeks) anesthetized male rats. Due to the high heart rate of rats, high-speed imaging was used to record retinal arterial pulsations without aliasing. Retinal video images were captured using a high speed camera (Optronis, Germany) at a rate of 250 frames per second for 10 seconds with a 50° field of view. A simultaneously recorded electrocardiogram was used in subsequent waveform analysis and heart rate (HR) calculation. Recorded video images were analysed with custom algorithms to measure arterial diameter pulsations at two sites 0.5 mm apart. PTT between the sites was calculated using the time delay of a fiducial point at 20% of the waveform height. Results: The average rPWV was 11.5±6.0 cm/s at a HR of 322±37 bpm, mean BP of 89±10 mmHg, and average retinal artery diameter of 54±11 μm. A positive correlation was obtained between arterial diameter and pulse amplitude (r²=0.52). The correlation between rPWV and HR was r²=0.32. Conclusion: This study confirmed the feasibility of a novel approach to measure rPWV in animal models. This technique is a promising accessible tool for microvascular assessment of PWV. The inter-individual variability is likely related to variations in depth of anesthesia and blood pressure which needs to be controlled to improve reproducibility. Future studies are required to assess the significance of PWV in the retinal microvasculature in rat models of cardiovascular disease.1 page(s

Relationship between retinal venous pulsatility and intraocular pressure changes

Purpose: Spontaneous retinal venous pulsations (SRVP) result from an interaction between intraocular pressure (IOP), retinal venous pressure (RVP) and intracranial pressure (ICP). With elevated ICP, raised RVP or reduced IOP, the intravascular pressure gradient across the prelaminar and retrolaminar portions of the central retinal vein decreases, leading to cessation of SRVP. This study examined the amplitude of SRVP and its relationship with IOP in retinal veins near the optic disc. Methods: 10 healthy subjects (35 ±10yrs) with no history of eye disease, a normal fundus on ophthalmoscopy with no vascular changes or signs of raised ICP were included. Baseline IOP/central corneal thickness (CCT) was measured and then SRVP recorded using the Dynamic Retinal Vessel Analyser (Imedos). IOP was lowered using Iopidine 0.5% and measured every 15 minutes, followed by dynamic recording of SPRV for 100 seconds - inferotemporal vein 1DD from optic disc. Mean SRVP was determined for a 20 sec period of stable recording within each sample at the same site on the vein. The blood pressure and heart rate were tracked continuously throughout (Finipress). RVP was assumed to be constant. The response to Timolol 0.5% was also tested in 2 subjects. Results: SRVP decreased in all subjects with reduction of IOP, but pulsations remained visible at the disc and measurable in the adjacent retinal vein. Group mean peak to peak SRVP was 10.75±4.9 um at baseline and reduced to 3.26±1.28 um after 45 minutes (p<0.0001). IOP fell from 15.5±2.5 mmHg to 10.8±2.9 mmHg over the same period (p<0.005). Mean venous diameter (155 microns), mean blood pressure (103 mmHg) and mean heart rate (74 bpm) did not change significantly with Iopidine application. Similar changes were observed with Timolol suggesting this is not simply a local drug effect on the ocular circulation. Conclusions: The findings support previous theories that suggest SRVP occurs due to a pressure gradient over the central retinal vein. SRVP can be reduced by manipulation of IOP downwards with medical treatment. Using this concept further experiments could be designed to extract an index between SRVP and ICP and possibly provide a novel method for predicting ICP non-invasively.1 page(s