Assessment of retinal arteriolar tortuosity in patients with COL4A1 or COL4A2 mutations.

Qualitative and quantitative analyzes of retinal arteriolar tortuosity (RAT) in patients with COL4A1 and COL4A2 mutations to identify a tortuosity index (TI) threshold for detecting increased RAT. Fifty-two eyes of 28 patients were included. Group 1 included eyes with a normal arteriolar pattern (n=19, 37%), group 2 included eyes with moderately increased arteriolar tortuosity (n=13, 25%), and group 3 included eyes with typical abnormal arteriolar tortuosity (n=20, 38%). The TI was measured by calculating the arc-to-chord ratio of arterioles and venules in the posterior pole. The mean arteriolar TI was significantly higher in all groups with a COL4A1/A2 mutation compared to controls: 1.19 ± 0.03, 1.24 ±0.05, and 1.57 ± 0.23 in groups 1, 2 and 3, respectively, vs. 1.12 ± 0.01 (all p <0.0001). The TI threshold was 1.13, with a sensitivity of 98.1% and a specificity of 100%. The area under the curve was 0.995. Measuring the arteriolar TI allowed diagnosing increased RAT in all eyes with a COL4A1/A2 mutation, whereas the subjective assessment suspected or detected it in only 62% of eyes. In adult patients with cerebral microangiopathy, detecting increased RAT, even when mild, directs the diagnosis towards COL4A1/A2-related cerebroretinal angiopathy.