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Marvin Cruz, Jessica Pottenburgh, Victoria Yu Chen, Christopher Le, Osamah Saeedi; Assessment of erythrocyte velocities in the retina and nailfold of glaucoma subjects and controls. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2586.
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© ARVO (1962-2015); The Authors (2016-present)
Blood flow is important to multiple ocular diseases and has been shown to be impaired in patients with glaucoma. Nailfold capillaroscopy visualizes peripheral capillaries and their blood flow while erythrocyte mediated angiography (EMA) precisely and accurately quantifies retinal blood flow. The purpose of this study is to compare the velocities of erythrocytes in the retina and nailfold.
We conducted a cross-sectional study using EMA in twenty-six patients to determine retinal venular, arteriolar, and capillary velocities, and a subset of seven patients underwent nailfold capillaroscopy. EMA uses ICG loaded erythrocytes to directly visualize blood flow in the retina and find erythrocyte velocities via a scanning laser ophthalmoscope (Tracey et al., Scientific Reports, 2019). Nailfold video capillaroscopy is a non-invasive approach to visualize capillaries at the fingernail base (Cousins et al., British Journal of Ophthalmology, 2019). By tracking blood gap displacement in the capillaries through the image frames, erythrocyte velocities were obtained.
Average retinal arteriolar velocities for control (7.60 ± 2.16 mm/s), glaucoma suspect (6.82 ± 1.67 mm/s), and glaucoma subjects (7.84 ± 2.62 mm/s) were not significantly different from each other (p = 0.30). However, average retinal venular velocities for control (5.00 ± 1.57 mm/s), glaucoma suspect (6.78 ± 1.63 mm/s), and glaucoma subjects (6.41 ± 1.46 mm/s) significantly differed (p = 0.0016). Average nailfold capillary velocity was not significantly different (p = 0.11) among control (0.301 ± 0.119 mm/s), glaucoma suspect (0.242 ± 0.103 mm/s), or glaucoma subjects (0.394 ± 0.153 mm/s). Retinal capillary velocities were obtained in seven subjects with a mean of 1.54 ± 0.35 mm/s.
Retinal capillary velocities are markedly higher than nailfold capillary velocities, consistent with the high metabolic rate of the retina. While nailfold capillary velocities are more accessible, a higher degree of precision may be necessary to detect differences given the lower velocities. Our nailfold capillary velocities were within range of what is reported in literature. Future work will compare nailfold capillary velocities to retinal capillary velocities in controls, glaucoma, and glaucoma suspects.
This is a 2021 ARVO Annual Meeting abstract.
Blood gap in contrasted nailfold capillary (A) and EMA-OCTA overlay showing path of erythrocyte in retinal capillaries (B).
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