Large Hypertransmission Defects Exhibit Choriocapillaris Flow Speed Impairment in Nonexudative Age-Related Macular...

To investigate choriocapillaris (CC) blood flow speed in regions associated with hypertransmission defects (hyperTDs) in nonexudative age-related macular degeneration (AMD) using variable interscan time analysis (VISTA) OCT angiography (OCTA).

Retrospective cross-sectional analysis of a prospectively collected cohort.

Thirty-one eyes from 29 subjects with nonexudative AMD.

Patients with age-related macular degeneration were imaged using a 600 kHz A-scan rate prototype swept-source OCT with a 5 × 5 mm field of view and 5 B-scan repeats (1.25 ms interscan time). Hypertransmission defects were traced on choroidal en face projections and categorized by their greatest linear dimension (GLD): large (≥250 μm), medium (63-250 μm), and small (<63 μm). Choriocapillaris blood flow speed was quantified using VISTA, which measures OCTA signal saturation dynamics across multiple interscan times. Variable interscan time analysis flow speed (VFS) was evaluated at the macula and within hyperTDs. Choriocapillaris flow speed impairment (ΔVFS) for each hyperTD was calculated as the difference between its VFS and the macular average. To assess spatial extent, ΔVFS was assessed beyond lesion boundaries. Traditional metrics of OCTA signal and flow deficits (FDs) were also evaluated.

Choriocapillaris blood flow speed impairment (ΔVFS) within and around hyperTDs.

The macular average CC VFS was 1.47 ± 0.34 ms^-1, with no significant difference between eyes with (n = 14) and without (n = 17) hyperTDs. A total of 88 hyperTDs were analyzed: 19 large, 28 medium, and 41 small. Large hyperTDs showed significant CC flow impairment (ΔVFS = -0.37 ± 0.18 ms^-1, P_adjusted < 0.0001), with impairment extending 100 μm beyond lesion boundaries (P_adjusted = 0.0061). Medium-sized hyperTDs demonstrated moderate impairment (ΔVFS = -0.30 ± 0.47 ms^-1, P_adjusted = 0.031), while small hyperTDs did not. In linear mixed-effects modeling, large and medium hyperTDs were associated with significant reductions in flow speed (-0.40 ms^-1, P = 0.014; -0.31 ms^-1, P = 0.030, respectively), corresponding to approximately 25% decreases from macular average. OCT angiography signal and FD metrics also detected size-dependent flow impairment.

Large hyperTDs in nonexudative AMD exhibit reduced CC flow speed extending beyond the lesion boundary. Longitudinal studies will investigate whether CC flow predicts onset and progression of hyperTDs.

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