ABSTRACT
We rely on newly-developed realized semicorrelations constructed from high-frequency returns together with hierarchical clustering and cross-validation techniques to identify groups of individual stocks that share common features. Implementing the new procedures based on intraday data for the S&P 100 constituents spanning 2019-2020, we uncover distinct changes in the “optimal” groupings of the stocks coincident with the onset of the COVID-19 pandemic. Many of the clusters estimated with data post-January 2020 evidence clear differences from conventional industry type classifications. They also differ from the clusters estimated with standard realized correlations, underscoring the advantages of “looking inside” the correlation matrix through the lens of the new realized semicorrelations. © 2021 Elsevier B.V.
ABSTRACT
Purpose : Vision Threatening Diseases (VTD) (age-related macular degeneration [AMD], cataract, diabetic retinopathy [DR], and glaucoma) account for 37% of all blindness. Screening and follow-up are crucial in preserving vision. During COVID-19, clinics reduced access, using telemedicine for diagnosis and follow-ups. The efficacy of remote screening and triage in the management of single or multiple VTDs was evaluated. Methods : We screened 41 subjects (19-85 years, 37% male, 17% Caucasian) (20 controls, 21 subjects). Demographics, 45-degree retinal photos, ganglion cell complex (GCC), and optic nerve head (ONH) images were collected using a non-contact puff-tonometer, nonmydriatic retinal camera, and an OCTA. Demographics and images were transmitted to two readers (onsite telemedicine screener [TS] and remote ophthalmologist [RO]) for triage. Triage was categorized: immediate referral to specialist, follow-up in person via clinic or telemedicine visit, or no follow-up necessary during COVID. Results : TS made 19 referrals (46%), 6 in person follow-ups (15%), 15 no follow-ups (37%);RO made 17 referrals (41%), 2 in person follow-ups (5%), 22 no follow-ups (54%). TS identified 12 subjects as possible VTD(s) while RO identified 11 subjects. TS and RO agreed on 8 glaucoma, 7 cataract, 3 DR, and 3 and 2 AMD cases, respectively. Glaucoma was identified using IOPs, retinal fundoscopy, and OCT imaging. Mean intraocular pressures were 12.9 and 15.7 (OD, OS) in glaucoma and 14.2 and 14.0 in controls. Fundoscopy was used for overall retinal health while OCT images were used to analyze GCC, ONH, nerve fiber layer, cup to disc ratio, and anterior chamber angles. AMD and DR were identified by fundoscopy and OCT imaging. 11 of the subjects were known clinic patients;both RO and TS referred all 11 to specialty clinics, matching the in-person clinic management. Conclusions : During the COVID pandemic, triaging patients can minimize person-toperson contact and help control the spread of the virus. Both readers agreed on the management and triage of a variety of patients with TS and RO differing only on 2 referrals and 4 in person follow-ups. Telemedicine is a promising alternative to in-person patient care for management and triage of vision threatening diseases. Further enrollment and follow-up are needed to increase robustness.
ABSTRACT
Purpose : The Centers for Disease Control reports 28.2% of surveyed US adults had reduced access to medical care (June/August 2020) due to the COVID-19 pandemic, with 8.9% reporting reduced access to vision care. A non-mydriatic digital retinal camera was piloted for deployment to the Emergency Department (ED) to help address this gap in vision care. Referrals for clinical follow-up in vision threatening diseases (VTDs) such as age-related macular degeneration, cataracts, diabetic retinopathy (DR), and glaucoma were assessed with human readers. Artificial Intelligence (AI) deep learning software was evaluated in known DR cases. Methods : 33 patients with known VTDs (48.48% male, avg 59.33 years) and 36 control subjects (41.67% male, avg 31.33 years) were included in tele-ophthalmology screening. A Canon CR-2 Plus AF non-mydriatic retinal camera captured 45-degree angle color and auto-fluorescence images of the eyes. Images (136 eyes) were graded by a certified telemedicine reader on site and an off-site clinical ophthalmologist following International Clinical Diabetic Retinopathy Disease Severity Scale (ICDRSS). Intergrader agreement between readers was evaluated with Cohen's kappa. An automated deep learning screening software optimized for DR (SELENA+, EyRIS Pte Ltd, Singapore) performed independent validation of readable color fundus images (17 eyes). Results : 5.07% of images were deemed unreadable by graders due to poor quality. Intergrader agreement for subject referral was κ = 0.710 (95% CI 0.545-0.875, p<.0005), with the clinical ophthalmologist generating more referrals than the telemedicine reader. Readers had 96.97% sensitivity (95% CI 91.12-1.028) and 72.22% specificity (95% CI 57.59- 86.85) in detecting referable disease. Positive predictive value was 76.19% (CI 63.31%- 89.07%) and negative predictive value was 96.30% (CI 89.17%- 1.034%). Of the 10 false positives, 6 were referred for rule out of glaucoma. Four had early stage cataracts that were deemed nonurgent. SELENA+ referred 100% of the known 9 DR patients. Conclusions : Tele-ophthalmology deployment in the ED helps limit patient and staff exposure to SARS-CoV-2 without sacrificing evaluation for VTDs. Tele-ophthalmology readers err on the side of caution to avoid missing VTD in a given patient. Use of AI can help keep strict adherence to referral guidelines.
ABSTRACT
Purpose : Coronavirus-19 (COVID-19) has had immense effects on access to medical care. Loss of medical care is alarming for individuals with pre-existing conditions like Type 1 Diabetes Mellitus (T1DM) which require uninterrupted care for best outcomes. Consistent care and medication use can reduce risk of developing diabetic retinopathy (DR) by 76% or progression by 54%. Healthy habits have also been linked to reduced risk of DR. The purpose of this study is to assess the effect of COVID-19 on care access and health habits in individuals with T1DM Methods : Surveys were administered from July-November of 2020 to multinational groups including the Children with Diabetes Conference (USA) and online groups, the American Diabetes Association and Connected in Motion Canadian Conference for T1DM. Data was collected from 125 patients from the USA, UK, Canada, and Bolivia. Age range was 5-81, and average years with T1DM was 17.9. The survey was online so responder rate is unclear, though response rates from previous surveys with similar groups averaged less than 10%. Results : While 73.6% of respondents saw an ophthalmologist within 1 year and 98.4% had medication without rationing, 40% postponed medical visits. Reasons for postponement included lack of appointments or transportation, financial issues and safety concerns. The majority (86.4%) were from the US where private insurance is prevalent, 12% were from Europe and Canada, where socialized medicine is common. Of respondents, 90.4% are willing to use telemedicine as an alternative. For most, diet remained the same (48.8%);25.6% stated their diet was healthier and 20% stated their diet was less healthy. 16.8% had problems accessing their usual foods due to the pandemic. A majority (55.2%) reported decreased exercise with 18.4% reporting more exercise. These overall trends were consistent across countries, and gender trends remained the same as pre-COVID, with women having better lifestyle and medical care adherence. Conclusions : Though patients delayed appointments, most were able to see an ophthalmologist and access medication. Physical activity levels decreased, though diets were mostly unchanged. In individuals with T1DM, disruptions in medical care and health habits can have negative long-term outcomes on overall and eye health. Telemedicine offers a promising solution for mitigating this risk.