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Abhishek Rege, Samantha I Cunningham, Yusi Liu, Karan Raje, Sachin Kalarn, M. Jason Brooke, Osamah Saeedi; Clinical Measurement of Retinal Blood Flow using the XyCAM RITM Handheld Retinal Imager. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5925.
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© ARVO (1962-2015); The Authors (2016-present)
The ability to non-invasively acquire quantitative morphological and blood flow measurements in a primary care setting has the potential to enable early and effective diagnoses of debilitating ophthalmic and systemic conditions. Our team has developed a handheld retinal imager—the XyCAM RITM—that can complement fundus images with retinal blood flow (RBF) measurements. Here, we present proof of concept results obtained from clinical investigation of the handheld use of the XyCAM RI.
The handheld XyCAM RI (weight < 1.05kg, length < 30cm) performs fundus photography in green illumination and laser speckle contrast imaging (LSCI) using red laser illumination. During clinical investigation, an ophthalmologist used the handheld XyCAM RI to image the right eye of 4 healthy individuals (58-59 years old, 2 male) through a dilated pupil. No accessories were used for stabilization of the device or the subject’s head. Upon focusing on a retinal region of interest (ROI) that includes the optic nerve head, 5 fundus photographs and 120 speckle images were acquired in rapid succession. Since this use case is susceptible to motion artifact, 4 imaging sessions were conducted and the most reproducible image was considered for analysis. Reference images were obtained using a Topcon TRC 50DX fundus camera. At least 4 vessel ROIs were identified in each image and retinal blood flow velocities (RBFV) were estimated within those ROIs using LSCI-based methods.
The vessel ROIs included in the analysis had a mean RBFV of 93.39 ± 39.479. Intra-session coefficient of variation (CV) was estimated across images generated from 8 sub-stacks of 15 speckle images each in the imaging session and aggregated for all subjects. CV for handheld RBFV estimates was low [7.37% ± 2.91] and comparable with a use case wherein both device and subject’s head are stabilized [p > 0.10]. Discriminability of vessels against background tissue (contrast ratio) in fundus photographs obtained using the handheld and fixed XyCAM RI was found to be similar to the reference images [p’s > 0.10].
The handheld XyCAM RI was able to reliably capture RBFV information from the retinas of all 4 subjects. While further development and continued clinical investigation is necessary, these early results suggest that handheld use of the XyCAM RI may be a feasible strategy and may lead to the realization of a valuable point-of-care tool.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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