Label-Free Density Measurements of Radial Peripapillary Capillaries in the Human Retina

Radial peripapillary capillaries (RPCs) comprise a unique network of capillary beds within the retinal nerve fibre layer (RNFL) and play a critical role in satisfying the nutritional requirements of retinal ganglion cell (RGC) axons. Understanding the topographical and morphological characteristics of these networks through in vivo techniques may improve our understanding about the role of RPCs in RGC axonal health and disease. This study utilizes a novel, non-invasive and label-free optical imaging technique, speckle variance optical coherence tomography (svOCT), for quantitatively studying RPC networks in the human retina. Six different retinal eccentricities from 16 healthy eyes were imaged using svOCT. The same eccentricities were histologically imaged in 9 healthy donor eyes with a confocal scanning laser microscope. Donor eyes were subject to perfusion-based labeling techniques prior to retinal dissection, flat mounting and visualization with the microscope. Capillary density and diameter measurements from each eccentricity in svOCT and histological images were compared. Data from svOCT images were also analysed to determine if there was a correlation between RNFL thickness and RPC density. The results are as follows: (1) The morphological characteristics of RPC networks on svOCT images are comparable to histological images; (2) With the exception of the nasal peripapillary region, there were no significant differences in RPC density measurements between svOCT and histological images; (3) Capillary diameter measurements were significantly greater in svOCT images compared to histology; (4) There is a positive correlation between RPC density and RNFL thickness. The findings in this study suggest that svOCT is a reliable modality for analyzing RPC networks in the human retina. It may therefore be a valuable tool for aiding our understanding about vasculogenic mechanisms that are involved in RGC axonopathies. Further work is required to explore the reason for some of the quantitative differences between svOCT and histology

Educational outcomes of the University of Toronto Visiting Professor Rounds Series

Objective: To assess how the University of Toronto Visiting Professors Rounds Series (UTVPRS) influenced the knowledge, perceptions, and clinical decision making of Canadian ophthalmologists. Design: Longitudinal cross-sectional. Participants: Eight hundred and fifty ophthalmologists registered with the Canadian Ophthalmological Society. Methods: Online surveys, using multiple-choice and reflection questions, were administered before and after online viewing of the University of Toronto Ophthalmology grand rounds as screencasts. Results: At 18 months, 124 users registered and watched 429 screencasts. Most participants found UTVPRS to be organized and user friendly. Mean prescreencast correct scores were 1008 versus 1288 postscreencast (p = 0.002). Postscreencast, 73% of participants replied in favour of changing future practice. Conclusions: UTVPRS was well received with demonstrated knowledge gain and potential practice change. The long-term and patient-related outcomes of the results require further research. © 2014 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.Link_to_subscribed_fulltex

Academic screencasting: Internet-based dissemination of ophthalmology grand rounds

Objective: To evaluate and compare the preferences and attitudes of Ontario ophthalmologists and ophthalmology residents toward screencasting as an educational tool with potential use for continuing medical education (CME) events. Design: Cross-sectional study. Participants: Eighty of 256 participants completed the survey. Methods: The surveys were sent to participants by email, with follow-up via telephone. Study participants were urban and rural Ontario ophthalmologists, registered with the Canadian Ophthalmological Society, and University of Toronto ophthalmology residents. Pre-recorded online presentations - screencasts - were used as the main intervention. Online surveys were used to measure multiple variables evaluating the attitudes of the participants toward screencasting. This data was then used for further quantitative and qualitative analysis. Results: Over 95% of participants replied favourably to the introduction and future utilization of screencasting for educational purposes. Rural ophthalmologists were the most enthusiastic about future events. Practising in rural Ontario was associated with a higher interest in live broadcasts than practising in urban centres (p<0.02), an association supported by qualitative data. Qualitative analysis revealed geographic isolation, busy schedules, ease of use/access, and convenience to be the key factors contributing to interest in screencasting. Conclusions: Practising ophthalmologists and residents in Ontario are interested in academic online screencasting. Rural ophthalmologists were more interested in live lectures than their urban colleagues. More research is required to assess the potential of screencasting as a CME tool.Link_to_subscribed_fulltex

Methodology for quantitative measurements.

<p>Representative speckle variance optical coherence tomography (svOCT) image (A) and histology image (B) from the nasal peripapillary region illustrates the technique used to acquire quantitative measurements. Capillary density was determined by calculating the number of intersections between capillaries (circles) and a perpendicular, straight line (red line) drawn through the capillary network. Results were expressed as intersections per 100 μm. Capillary diameter was determined by calculating the perpendicular distance across the maximum chord axis of each vessel. This is as illustrated in the corresponding magnified regions (outlined in yellow dashed lines) of svOCT (C) and histology (D) images. Scale bar = 120μm (A & B) and 60μm (C and D)</p

Scatter plot of intercapillary distance (ICD) and retinal nerve fibre layer thickness (RNFL) with the speckle variance optical coherence tomography.

<p>Each region is colour coded. Sup = Superior; ST = Supero-temporal; Temp = Temporal; IT = Infero-temporal; Inf = Inferior and N = Nasal. Unit of measurement in both axes is in microns.</p

Regions where radial peripapillary capillary network morphology and topography were studied quantitatively.

<p>Insets placed on a fluorescein angiogram illustrate the six different eccentricities that were studied with speckle variance optical coherence tomography and histology. Sup = Superior; ST = Supero-temporal; Temp = Temporal; IT = Infero-temporal; Inf = Inferior and N = Nasal regions.</p

A paired graphical representation of quantitative comparisons between speckle variance optical coherence tomography (svOCT) and histology data for the six eccentricities.

<p>The averaged value is presented as solid bars with standard deviations presented by error bars. Black solid bars represent data from svOCT images whilst grey solid bars represented data from confocal images. Data presented include (A) number of RPCs per 100 μm, (B) Inter-capillary distance or ICD in microns, and (C) RPCs diameter in microns. The data are presented as per study region and include the supero-temporal (ST), infero-temporal (IT), superior (Sup), temporal (Temp), inferior (Inf) and nasal (Nasal). Statistically significant difference (p<0.05) between the two techniques are marked with an asterisk.</p