title: Label-Free Density Measurements of Radial Peripapillary Capillaries in the Human Retina.
abstract: 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.
authors.affiliation: Centre for Ophthalmology and Visual Science, The University of Western Australia, Australia, Perth, Australia; Lions Eye Institute, The University of Western Australia, Perth, Australia.
authors.forename: Paula K
authors.initials: PK
authors.lastname: Yu
authors.affiliation: Centre for Ophthalmology and Visual Science, The University of Western Australia, Australia, Perth, Australia; Lions Eye Institute, The University of Western Australia, Perth, Australia; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada.
authors.forename: Chandrakumar
authors.initials: C
authors.lastname: Balaratnasingam
authors.affiliation: School of Engineering Science, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.affiliation: Centre for Ophthalmology and Visual Science, The University of Western Australia, Australia, Perth, Australia; Lions Eye Institute, The University of Western Australia, Perth, Australia.
authors.forename: William H
authors.initials: WH
authors.lastname: Morgan
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada.
authors.forename: Zaid
authors.initials: Z
authors.lastname: Mammo
authors.affiliation: School of Engineering Science, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Sherry
authors.initials: S
authors.lastname: Han
authors.affiliation: School of Engineering Science, Simon Fraser University, Burnaby, British Columbia, Canada; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Mackenzie
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Merkur
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kirker
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Albiani
authors.affiliation: School of Engineering Science, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Marinko V
authors.initials: MV
authors.lastname: Sarunic
authors.affiliation: Centre for Ophthalmology and Visual Science, The University of Western Australia, Australia, Perth, Australia; Lions Eye Institute, The University of Western Australia, Perth, Australia.
authors.forename: Dao-Yi
authors.initials: DY
authors.lastname: Yu
mesh_terms: D000328:Adult; D001369:Axons / Q000473:pathology / Q000502:physiology; D002196:Capillaries / Q000502:physiology*; D003196:Computer Graphics; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D018613:Microscopy, Confocal; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology; D061848:Optical Imaging; D012160:Retina / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000166:cytology*; D012171:Retinal Vessels / Q000502:physiology*; D041623:Tomography, Optical Coherence / Q000379:methods*