“The retina provides a window to study ocular, neurological and systemic conditions,” said study co-author Jianhua (Jay) Wang, M.D., Ph.D., associate professor of ophthalmology at Bascom Palmer. “Our work on the retina may open up a new era for examining and monitoring microvascular changes associated with diseases, such as stroke, hypertension and diabetes.
Jiang, who is also assistant professor of neurology, noted that the retinal capillary network is very similar to the network of small blood vessels in the brain and could provide a potential clinical indicator for abnormal neurological conditions. “We would expect to find a denser capillary network in healthy patients than in those with cerebrovascular disease,” she said. “Someone with mild symptoms, but a reduced capillary network, might be at higher risk. Once we better understand how the networks relate to diseases, we can start to provide clinical answers to physicians.”
The Miller School study, “Automated segmentation and fractal analysis of high-resolution non-invasive capillary perfusion maps of the human retina,” was published recently in Microvascular Research. Other Miller School authors were Bascom Palmer’s Delia Cabrera DeBuc, Ph.D., research associate professor of ophthalmology, Byron L. Lam, M.D., professor of ophthalmology, and Aizhu Tao, M.D., M.Sc., research associate; and Tatjana Rundek, M.D., Ph.D., professor of neurology, and Clinton B. Wright, M.D., associate professor of neurology. Meixiao Shen, Ph.D., M.Sc., of the School of Ophthalmology and Optometry at Wenzhou Medical College in China, also was a co-author.
The groundbreaking study involved six healthy subjects without a history of cerebral small vessel disease, hypertension, diabetes or kidney disease. The team analyzed the subjects’ capillary networks by using the Retinal Functional Imager, a non-invasive technology that does not require an injection of dye to highlight the blood vessels. Bascom Palmer is one of only six institutions in the U.S. with this technology.
For the fractal analysis of the retinal images, the Miller School researchers developed proprietary software to produce high-resolution, non-invasive capillary perfusion maps (nCPMs). Fractal analysis has been used in various branches of medicine – including the study of large blood vessels – to show differences in the structural patterns of cells, tissues and organs.
With fractal analysis, it is possible to provide a global and more natural description of complex branching structures, such as the retinal microvasculature.
Cabrera DeBuc said fractal analysis may be a more effective way to determine the health of the retina’s capillary network than analysis of the retinal vessel caliber in actual images, which is influenced by variations in ocular and camera magnification.
“Our study demonstrated that the automatic segmentation of nCPMs is feasible for fractal analysis,” she added. “These nCPMs reveal more information about small vessels than standard images of the retina.”
Pointing to the future, Jiang said, “Our research is still at an early stage. We will continue to study the small blood vessels of the eye, develop additional nCPMs features, and see how they correlate with the findings for magnetic resonance imaging scans. In that regard, this study may provide an important foundation for advancing our understanding of cerebral small vessel disease, lacunar stroke and other cerebrovascular-related diseases.”
The study was funded by a research supplement to Jiang, part of an NIH R01 grant awarded to Cabrera DeBuc.
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