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Mircea Mujat, Yang Lu, Nicusor Iftimia, R Daniel Ferguson; Ultra-widefield ocular vasculature imaging without contrast agent. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6107.
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To demonstrate a new approach for ultra-widefield imaging and flow quantification of ocular vasculature that enables hemodynamic studies in animals and human subjects. Vascular alterations are present in many eye diseases including age-related macular degeneration, diabetic retinopathy, and glaucoma. Improved analysis of the ocular vasculature could play an important role in diagnosing and monitoring eye diseases.
Two imaging modalities: line-scanning Doppler flowmetry (LSDF) and optical coherence tomography (OCT) are combined in the same instrument to provide complementary aspects of ocular blood flow. The wide-field semi-quantitative LSDF technique enables visualization and mapping of retinal and choroidal blood vessels without additional contrast agents. Standard OCT provides 3D structural information and Doppler OCT quantifies precise local flow parameters. Speckle-variance OCT generates local 3D mapping of blood flow.
Standard laser Doppler flowmetry (LDF) provides Velocity, Volume, and Flow maps. Parallel scanning in LSDF enables orders of magnitude speed increase as compared to LDF which in turn affords imaging much larger areas and visualization of much faster flow. Retinal and choroidal flow is mapped non-invasively without the use of fluorescein or indocyanine green. The entire choroidal vasculature of the posterior eye hemisphere is imaged including the vortex veins that drain the choroid, therefore allowing for quantification of the total choroidal flow. A gallery of vortex veins from multiple volunteers is shown in Fig. 1 as Velocity maps. Simultaneously, OCT raster scans are acquired with B-scan repetition (5). Average of repeated B-scans provides noise reduction, while inter-frame speckle variance provides 3D visualization of the retinal blood vessels. Layer segmentation can be used to generate thickness maps for RNFL, retina, and choroid. Circular scans at specific locations provide quantitative flow values.
The ability of these two complementary imaging modalities (LSDF and OCT) to map retinal and choroidal blood vessels and quantify ocular blood flow has been demonstrated. Such an advanced diagnostic imaging system will help understanding hemodynamic processes in the eye as a response to disease or treatment.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Figure 1. Examples of vortex veins (indicated by the red *) visualized with LSDF and illustrated as velocity maps.
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