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Salman Sarwar, Mohamed Kamel Soliman, Muhammad Hassan, Mohammad Ali Sadiq, Aniruddha Agarwal, Rubbia Afridi, Kanika Aggarwal, Diana V Do, Quan Dong Nguyen, Yasir Jamal Sepah; Diurnal Variation of Choriocapillaris Vessel Flow Density in Normal Subjects Measured using Optical Coherence Tomography Angiography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4612.
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© ARVO (1962-2015); The Authors (2016-present)
Vessel flow density (VFD) may provide important information regarding perfusion status. Diurnal variation in VFD of choriocapillaris has not been reported in literature. In the index study, optical coherence tomography angiography (OCTA) was used to assess the diurnal variation of the VFD in the choriocapillaris of subjects with no known ocular disease.
Twenty eyes with no known ocular disease (10 subjects) were included. OCTA images were acquired using Optovue RTVue XR 100 at two time points on a single day: 9:00 AM and 6:00 PM. Macular cube scan protocol (3X3 mm) centered on the fovea was used. Automatic segmentation of the retinal layers and choriocapillaris (Figure 1) was performed using ReVue software (Version: 2015.1.0.71), which was also used to measure the choriocapillaris VFD by an independent grader. Horizontal line scan passing through the fovea was obtained by the OCTA device at both time points and ReVue linear measurement tool was used to measure subfoveal CT perpendicularly from the outer edge of the retinal pigment epithelium to the inner sclera (Figure 2). Wilcoxon signed-rank test was used to assess the differences in choriocapillaris VFD and subfoveal CT at the two time points. Correlation between change in choriocapillaris VFD and subfoveal CT at the two time points was assessed using Pearson correlation coefficient (r).
The mean age of the subjects was 28.5 ± 4.08 years. Choriocapillaris VFD was significantly higher at 9:00 AM compared to 6:00 PM (P= 0.0001) with mean choriocapillaris VFD of 64.18 ± 2.27% at 9:00 AM, 62.69 ± 2.2% at 6:00 PM, and mean diurnal amplitude of 1.49%. Mean subfoveal CT was 309.72 ± 46.12 µm at 9:00 AM and 288.91 ± 44.07 µm at 6:00 PM. Subfoveal CT was also significantly higher at 9:00 AM compared to 6:00 PM (P<0.0001) with a mean diurnal amplitude of 20.82 µm. Change in choriocapillaris VFD correlated with change in subfoveal CT (r=0.87).
OCTA demonstrated significant diurnal change in choriocapillaris VFD in subjects without any ocular disease with VFD higher in the morning and lower in the evening. Decrease in choriocapillaris VFD in the evening correlated with a reduction in subfoveal CT.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
OCTA at the level of the choriocapillaris. The yellow area depicts flow of the RBC’s within the choriocapillaris.
OCT scan shows subfoveal CT measured using ReVue software (orange line)
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