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Richard Haindl, Andreas Wartak, Wolfgang Trasischker, Bernhard Baumann, Michael Pircher, Christoph K Hitzenberger; Total retinal blood flow in healthy and glaucomatous human eyes measured with 3 beam Doppler optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2969.
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© ARVO (1962-2015); The Authors (2016-present)
Two principal theories, a mechanical and a vascular, have been described for glaucomatous optic neuropathy (GON) development. To evaluate the vascular theory, exact and quantitative total retinal blood flow (RBF) measurements are still necessary. Therefore we evaluate the potential and repeatability of 3 beam Doppler optical coherence tomography (D-OCT) with regard to RBF measurements in healthy and glaucomatous human eyes to learn about alterations in RBF and velocity.
The 3 beam D-OCT consists of 3 independent spectral domain OCT subsystems operating at 50 kA-scans/s each. A well-defined beam geometry enables the full reconstruction of the 3 dimensional velocity vector without prior knowledge on the vessel geometry, which is normally required for D-OCT systems with less than 3 beams.Twenty healthy and 5 glaucomatous eyes were imaged, employing a circular scan pattern around the optic nerve head (ONH). The mean RBF was measured for arteries and veins in both groups. The reproducibility of the method was evaluated for the mean RBF flow in 6 healthy eyes. Furthermore the RBF between healthy and glaucomatous eyes was compared.
Averaged over 20 healthy eyes, the total venous and arterial mean blood flow was measured to be 47.1 ± 2.7 µl/min and 47.1 ± 2.4 µl/min respectively. The average coefficient of variation was ~ 6% (6 eyes, total flow). In the glaucomatous eyes the total venous and arterial mean flow averaged over 5 eyes was found to be reduced and measured with 36.1 ± 2.3 µl/min and 35.9 ± 1.7 µl/min respectively. A two-sample t-test between healthy and glaucomatous eyes yielded a highly significant difference in RBF between the two groups (p < 0.001). Fig. 1 shows a comparison between healthy and glaucomatous eyes.
Three beam D-OCT allows the direct measurement of total retinal blood flow and velocity independent from any a-priory knowledge on the vessel geometry. The average variance for total flow measurements is sufficiently small to measure the reduced blood flow in glaucomatous eyes. In the future 3 beam D-OCT may aid in the early diagnosis of glaucoma, evaluate the relevance of targeting ocular blood flow in treatment modalities and might be the proper tool to evaluate the vascular theory behind GON development.
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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