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/mm2 [95% CI: 17.58-19.86] and 32.34% [95% CI: 29.95-34.92] in group 1 vs. 18.32 mm/mm2 [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 mm2 [95% CI: 0.157-0.354] vs. 0.293 mm2 [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.