June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Noninvasive imaging of retinal blood vessels and blood flow using a custom, non-mydriatic, handheld optical imager designed for use in primary care and telehealth settings
Author Affiliations & Notes
  • Abhishek Rege
    Vasoptic Medical, Inc., Columbia, MD
  • Karan Raje
    Vasoptic Medical, Inc., Columbia, MD
  • Marin Kheng
    Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD
  • Antonella Mangraviti
    Department of Neurosurgery, Johns Hopkins University, Baltimore, MD
  • Karansingh Thakur
    Vasoptic Medical, Inc., Columbia, MD
  • Betty Tyler
    Department of Neurosurgery, Johns Hopkins University, Baltimore, MD
  • Nitish V Thakor
    Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD
  • M Jason Brooke
    Vasoptic Medical, Inc., Columbia, MD
  • Ingrid E Zimmer-Galler
    Wilmer Eye Institute, Johns Hopkins Medical Institutions, Baltimore, MD
  • Peter L Gehlbach
    Wilmer Eye Institute, Johns Hopkins Medical Institutions, Baltimore, MD
  • Footnotes
    Commercial Relationships Abhishek Rege, Vasoptic Medical Inc. (E), Vasoptic Medical Inc. (P), Vasoptic Medical Inc. (S); Karan Raje, Vasoptic Medical, Inc. (E); Marin Kheng, None; Antonella Mangraviti, None; Karansingh Thakur, Vasoptic Medical, Inc. (E); Betty Tyler, None; Nitish Thakor, Vasoptic Medical Inc. (P); M Jason Brooke, Vasoptic Medical Inc. (E), Vasoptic Medical Inc. (P), Vasoptic Medical Inc. (S); Ingrid Zimmer-Galler, None; Peter Gehlbach, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 5975. doi:https://doi.org/
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      Abhishek Rege, Karan Raje, Marin Kheng, Antonella Mangraviti, Karansingh Thakur, Betty Tyler, Nitish V Thakor, M Jason Brooke, Ingrid E Zimmer-Galler, Peter L Gehlbach; Noninvasive imaging of retinal blood vessels and blood flow using a custom, non-mydriatic, handheld optical imager designed for use in primary care and telehealth settings. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5975. doi: https://doi.org/.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

To investigate a custom, non-mydriatic, handheld imaging device designed to non-invasively capture vessel-specific retinal blood flow (RBF).

 
Methods
 

This investigational device is comprised of a dual-illumination, custom imaging instrument utilizing a combination of laser speckle contrast imaging (LSCI) and indirect ophthalmoscopy. Five adult Wistar rats were anesthetized with a xylazine-ketamine mixture for retinal imaging. The device was held by the operator with the elbow stabilized. Once focusing was achieved in white light illumination, ten fundus photographs were rapidly acquired. The illumination was then changed to red laser illumination and 160 sequential speckle image frames of the same field of view (FOV) were acquired in rapid succession (at 100 frames/second). Images of both eyes were acquired, capturing the optic nerve head and peripheral retina, providing 4 sets of images per animal. The acquired raw speckle images were processed to generate LSCI images, from which vessels were segmented manually (gold standard) and automatically (using custom software) to extract intravascular RBF using LSCI-based estimates of blood velocity and diameter.

 
Results
 

LSCI images of major retinal vessels were captured in a ~40° FOV, with the smallest vessel diameters measured at 30 µm. Vessels were well contrasted from the retinal tissue (mean contrast-to-noise ratios of 1.40 and 0.81 in the center and periphery respectively), providing intuitive fundus visualization, complemented with blood flow information (Fig. 1A-B). By analyzing the cross-sections of branching vessels, it was possible to validate the conservation of blood flow at branch points (Fig. 1C). The robustness of measurements is governed by an observed median variability (RMSE) of 5.4% between sequentially obtained intravascular flow-estimates.

 
Conclusions
 

This study shows the feasibility of capturing high-resolution images of RBF using a custom, handheld instrument without dye injection or pupil dilation. The functionality of this device exhibits a potential for early detection and improved disease management of various ocular and systemic diseases, while its portability shows promise to significantly impact healthcare delivery in underserved areas through deployment in primary care and telehealth settings.  

 
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