Analysis of macular and optic nerve vasculature using optical coherence tomography angiography in patients with human T-cell lymphotropic virus type 1

Purpose To compare macular and optic nerve head (ONH) microvasculature using optical coherence tomography angiography (OCT-A) in asymptomatic human T-cell lymphotropic virus type 1 (HTLV-1) carriers and patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), in search of potential biomarkers of disease development. Methods Pilot study analyzing quantitative OCT-A parameters of the macula and ONH vasculature in asymptomatic HTLV-1 carriers (group 1) and patients with HAM/TSP (group 2). Results Up to 41 eyes of 21 patients were included. Macular total vessel density and perfusion density (PD) were 18.72 mm/mm 2 [95% CI: 17.58–19.86] and 32.34% [95% CI: 29.95–34.92] in group 1 vs. 18.32 mm/mm 2 [95% CI: 17.06–19.58] ( p = 0.59) and 32.19% [95% CI: 29.45–35.16] ( p = 1) in group 2. Foveal avascular zone area, perimeter and circularity were similar in both groups (0.255 mm 2 [95% CI: 0.157–0.354] vs. 0.293 mm 2 [95% CI: 0.180–0.406], p = 0.41, 2.124 mm [95% CI: 1.782–2.531] vs. 2.344 mm [95% CI: 1.916–2.867], p = 0.41, and 0.634 [95% CI: 0.588–0.680] vs. 0.603 [95% CI: 0.551–0.655], p = 0.32, in group 1 vs. group 2 respectively). Peripapillary PD and flux index (FI) were 43.95% [95% CI: 42.90–45.03] vs. 43.19% [95% CI: 42.01–44.40], p = 0.29, and 0.425 [95% CI: 0.41–0.44] vs. 0.403 [95% CI: 0.38–0.42], p = 0.08, in group 1 vs. group 2, respectively. Conclusion Despite limitations related to sample size and disease rarity, this pilot study revealed no statistically significant differences in the macular and ONH microvascular parameters assessed by OCT-A between HAM/TSP patients and asymptomatic HTLV-1 carriers. Further investigations are needed in larger longitudinal multicenter studies regarding the peripapillary FI, which tends to be lower in patients with HAM/TSP.