Retinal imaging biomarkers of Alzheimer's disease: A systematic review and meta-analysis of studies using brain amyloid beta status for case definition.

Introduction: We performed a systematic review and meta-analysis of the association between retinal imaging parameters and Alzheimer's disease (AD). Methods: PubMed, EMBASE, and Scopus were systematically searched for prospective and observational studies. Included studies had AD case definition based on brain amyloid beta (Aß) status. Study quality assessment was performed. Random-effects meta-analyses of standardized mean difference, correlation, and diagnostic accuracy were conducted. Results: Thirty-eight studies were included. There was weak evidence of peripapillary retinal nerve fiber layer thinning on optical coherence tomography (OCT) (p = 0.14, 11 studies, n = 828), increased foveal avascular zone area on OCT-angiography (p = 0.18, four studies, n = 207), and reduced arteriole and venule vessel fractal dimension on fundus photography (p < 0.001 and p = 0.08, respectively, three studies, n = 297) among AD cases. Discussion: Retinal imaging parameters appear to be associated with AD. Small study sizes and heterogeneity in imaging methods and reporting make it difficult to determine utility of these changes as AD biomarkers. Highlights: We performed a systematic review on retinal imaging and Alzheimer's disease (AD).We only included studies in which cases were based on brain amyloid beta status.Several retinal biomarkers were associated with AD but clinical utility is uncertain.Studies should focus on biomarker-defined AD and use standardized imaging methods.

Efficacy of patient-sided breath shields for slit-lamp examination.

OBJECTIVE: To evaluate the efficacy of patient-sided breath shields in preventing oronasal droplet transmission during slit-lamp examination. DESIGN: Experimental study testing the efficacy of patient-sided breath shields on a slit lamp. METHODS: Two commercially available patient-sided breath shields and a 3-dimensional (3D)-printed shield designed by the authors were attached to a slit-lamp chin rest for testing. Each shield was exposed to 3 standardized sprays of coloured dye from a spray gun with its nozzle adjusted to simulate the angular dispersion of a human sneeze. Any overspray not blocked by the shields was recorded and compared with spray with no shield (control). Image-processing software was used to ascertain the surface area of overspray not blocked by the tested shield compared with the control of no shield. RESULTS: With typical use, both commercially available patient-sided shields and the 3D-printed shield blocked 100% of forward-travelling measurable droplets from a simulated sneeze spray. Even when set to the furthest distance setting to simulate the worst-case scenario, shield 1 and the 3D-printed shield blocked 99.96% and 99.65% of overspray, respectively. However, slow-motion footage did reveal that a considerable amount of spray rebounded off the shields and extended peripherally past its borders. CONCLUSIONS: With typical use, all tested shields prevented 100% of oronasal transmission. To encourage accessibility, the authors offer a free 3D model and instructions for creating the tested patient-sided breath shield. Patient-sided shields should be combined with other infection-control measures to minimize transmission.

Ocular Distribution of the Renin-Angiotensin-Aldosterone System in the Context of the SARS-CoV-2 Pandemic.

The COVID-19 pandemic has resulted in an unprecedented impact on global health, economy, and way of life. SARS-CoV-2, the virus responsible for the disease, utilizes the ACE2 receptor found on host cells to mediate entry, replication, and infection. Numerous studies have elucidated the presence of many components of the renin-angiotensin-aldosterone system (RAAS) in the eye, including the ACE2 receptor. Considering this, and the anatomical vulnerability that the exposed ocular surface offers with its interconnectedness to the respiratory system, there is a theoretical risk of pathogen entry from the ocular route as well as the development of COVID-19-associated eye disease. Despite this, the actual epidemiological data demonstrates low ocular symptoms, possibly due to differing ACE2 receptor expression across age, ethnicity, and sex coupled with the protective properties of tears. We summarize the current literature on ocular RAAS with specific focus on the ACE2 receptor and its interplay with the SARS-CoV-2 virus.

Evaluation of the initial implementation of a nationwide diabetic retinopathy screening programme in primary care: a multimethod study.

OBJECTIVES: The Australian Government funded a nationwide diabetic retinopathy screening programme to improve visual outcomes for people with diabetes. This study examined the benefits and barriers of the programme, image interpretation pathways and assessed the characteristics of people who had their fundus photos graded by a telereading service which was available as a part of the programme. DESIGN: Multimethod: survey and retrospective review of referral forms. SETTING: Twenty-two primary healthcare facilities from urban, regional, rural and remote areas of Australia, and one telereading service operated by a referral-only eye clinic in metropolitan Sydney, Australia. PARTICIPANTS: Twenty-seven primary healthcare workers out of 110 contacted completed a survey, and 145 patient referrals were reviewed. RESULTS: Manifest qualitative content analysis showed that primary healthcare workers reported that the benefits of the screening programme included improved patient outcomes and increased awareness and knowledge of diabetic retinopathy. Barriers related to staffing issues and limited referral pathways. Image grading was performed by a variety of primary healthcare workers, with one responder indicating the utilisation of a diabetic retinopathy reading service. Of the people with fundus photos graded by the reading service, 26.2% were reported to have diabetes. Overall, 12.3% of eyes were diagnosed with diabetic retinopathy. Photo quality was rated as excellent in 46.2% of photos. Referral to an optometrist for diabetic retinopathy was recommended in 4.1% of cases, and to an ophthalmologist in 6.9% of cases. CONCLUSIONS: This nationwide diabetic retinopathy screening programme was perceived to increase access to diabetic retinopathy screening in regional, rural and remote areas of Australia. The telereading service has diagnosed diabetic retinopathy and other ocular pathologies in images it has received. Key barriers, such as access to ophthalmologists and optometrists, must be overcome to improve visual outcomes.