Purpose: To investigate retinal capillary plexus capillary flow speed and vessel density in diabetic retinopathy and normal subjects using variable interscan time analysis optical coherence tomography angiography (OCTA).
Methods: High speed swept source OCTA imaging using multiple interscan times was performed over a 5 mm × 5 mm field-of-view with 600 kHz A-scan rate. Second-generation variable interscan time analysis OCTA was used to measure a surrogate marker for capillary blood flow speed, variable interscan time analysis flow speed (VFS), in the superficial and intermediate capillary plexuses VFS , and deep capillary plexus VFS . Vessel density was measured using OCTA.
Results: Fifty-seven eyes with different diabetic retinopathy severity and 37 normal eyes were analyzed. Variable interscan time analysis OCTA provided diverse blood flow speed information, including pseudo-color OCTA and mean flow speed in different regions. Both deep capillary plexus VFS and deep capillary plexus VFS /(superficial and intermediate capillary plexuses) VFS were higher in diabetic retinopathy compared with normal eyes. Elevated deep capillary plexus VFS correlated with decreased deep capillary plexus vessel density in nonproliferative diabetic retinopathy.
Conclusion: Variable interscan time analysis OCTA can measure a quantitative biomarker for blood flow speed alterations in diabetic retinopathy and normal eyes as well as the association with vessel density in different capillary plexuses. Variable interscan time analysis OCTA is promising for studies of pathogenesis and early flow alterations, which may precede nonperfusion.