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Alexander Gan, Nishit Shah, Moataz M Razeen, Alexander Pinhas, Eric Cheang, Rishard Weitz, Ronald Gentile, Alfredo Dubra, Toco Yuen Ping Chui, Richard B Rosen; In vivo microscopy using adaptive optics scanning light ophthalmoscope fluorescein angiography and analysis of the foveal microvasculature in sickle cell retinopathy and comparison with SD-OCT. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3871.
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To compare the foveal microvascular density in sickle cell retinopathy (SCR) with healthy controls using adaptive optics scanning light ophthalmoscope fluorescein angiography (AOSLO FA), and to compare with SD-OCT retinal thickness profiles.
AOSLO FAs of 3 SCR subjects (average age: 36 years; range: 32-42) using oral fluorescein (20 mg/kg) were acquired and compared to previously obtained healthy control data. Simultaneous reflectance (790nm) and fluorescence (488nm) image sequences covering a 6° square area centered at the fovea were acquired using a 1.75° field of view. Images were stitched together to create larger microvascular perfusion maps (Fig. 1A). The maps were skeletonized (Fig.1B) and Foveal Vessel Density (FVD) (mm-1) was calculated for a concentric annulus centered at the fovea (A=200-800µm). Inner Foveal Vessel Density (iFVD, 200-400µm radius) and Outer Foveal Vessel Density (oFVD, 400-800µm radius) were also calculated. To compare VD with retinal thickness, 12 SD-OCT radial scans centered at the fovea were acquired for each eye and segmented to measure inner retinal thickness (IRT), outer retinal thickness (ORT) and total retinal thickness (TT) at 50-750µm from the foveal center with a 100 µm interval. OCT thickness profiles were averaged. Statistical significance was assessed using an unpaired t-test.
Mean FVD was less in the SCR eyes compared to controls (34.8 ± 3.0 versus 41.8 ± 1.39 (mm-1), p=0.022). When comparing the inner and outer annuli, there was a significant decrease in the ORT thickness on SD-OCT in the outer annuli in SCR eyes versus controls (p=0.043). Although mean iFVD and oFVD in SCR were less than controls, the differences were not significant. (Fig.2).
The reduction in SCR VD compared to controls is indicative of microvascular abnormalities occurring in the foveal region. Our results indicate that VD analysis of AOSLO FAs may be a sensitive tool to detect subclinical changes to the foveal microvasculature, showing promise to gain more knowledge about SCR. Further studies with a larger sample size are needed to correlate VD with OCT thickness profiles.
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