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Eric Wei, Yali Jia, Ou Tan, Benjamin Potsaid, Jonathan Liu, WooJhon Choi, James Fujimoto, David Huang; Parafoveal retinal vascular response to pattern stimulation assessed with OCT angiography. Invest. Ophthalmol. Vis. Sci. 2013;54(15):399.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the parafoveal retinal vascular response to stimulation with a reversing checkerboard pattern using OCT angiography.
One eye of each subject was scanned with an ultra-high speed (100,000 A-scans/sec) 1050 nm wavelength swept-source OCT device. Each 3x3 mm OCT angiography image, comprised of a 200x200 scan pattern with 8 repeated B-scans at each position, was acquired in 3.4 seconds. Flow was detected from the decorrelation of signal amplitude between repeated B-scans using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. Parafoveal retinal flow index was calculated from en face maximum projections of the retinal layers by averaging decorrelation values within the parafoveal region defined by a 1 mm wide annulus surrounding the fovea avascular zone (FAZ). A reversing checkerboard pattern modulated at 8 cycles/second was used to stimulate the macula. The experimental sequence, performed twice for each subject, consisted of 1 minute of baseline, 2 minutes with stimulation on, and 1 minute of stimulation off, with scans of the macula captured in 15 second intervals.
Five normal subjects were evaluated. An increase of 6.09 ± 4.69% (mean ± standard deviation of 5 subjects) over baseline (p = 0.001, paired t-test) was observed during the first minute of stimulation and 1.96 ± 5.39% (p = 0.275) during the second minute. Following cessation of the pattern stimulus, a 0.40 ± 6.04% increase in flow index over baseline was observed (p = 0.896). The most significant change to flow index was seen 30 seconds into stimulation where a 7.12% ± 4.35% increase from baseline occurred (p < 0.001) (Fig. 1). The repeatability of the 4 consecutive baseline measurements within the same sequence was 1.3% coefficient of variation (CV). The repeatability between 2 baseline sequences was 2.1% CV.
OCT angiography with SSADA is able to detect increased flow in the parafoveal retinal vasculature in response to pattern stimulation. The response was large relative to the repeatability of baseline flow index measurements. However, the magnitude of the response was highly variable between individuals.
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