Biomarkers in Usher syndrome: ultra-widefield fundus autofluorescence and optical coherence tomography findings and their correlation with visual acuity and electrophysiology findings

Purpose: To investigate the functional and structural biomarkers and their correlation with Usher syndrome (USH). Methods: Medical records, imaging and electrophysiology test results of USH patients attending the Save Sight Institute between 2012 and 2017 were reviewed. Best corrected visual acuity (BCVA), ultra-widefield autofluorescence (UW-FAF), spectral-domain optical coherence tomography (SD-OCT), full-field electroretinogram and pattern electroretinogram (pERG) were performed. SD-OCT scans assessed central macular thickness (CMT), greatest linear diameter of preserved outer retinal layers—macular island (MI) and presence of cystoid macular edema (CME). UW-FAF images were qualitatively graded to identify hypo/hyperfluorescence patterns in the peripheral fundus. Results: Thirty-six eyes from 18 subjects were included. Mean BCVA was 0.22 ± 0.3 LogMAR. MI extent was significantly associated with better vision (β = − 0.175 per 1000 µm; R² = 0.487; P = 0.002; Fig. 4). A higher pERG P50 was associated with a larger macular island (β = 782 per µV; R² = 0.238; P = 0.025), while a higher pERG N95 was associated with a smaller macular island (β = − 499 per µV; R² = 0.219; P = 0.030). Mean CMT was 271 ± 35 μm and was significantly associated with better vision (β = − 0.083 per 10 µm; R² = 0.612; P < 0.001). CME was diagnosed in 47.2% (n = 17) eyes. There was no significant difference in mean BCVA for those with CME (0.19 ± 0.2 LogMAR) and without CME (0.40 ± 0.5; R² = 0.081; P = 0.17). All patients had abnormal UW-FAF. Four main patterns of change were identified (granular 55%, annular 11%, bone spicule 17% and patchy 17%). Patients with the patchy pattern demonstrated worse BCVA in comparison with those with granular (P < 0.0001) and bone spicule (P = 0.0179) patterns. Conclusions: Structural changes identified on OCT and UW-FAF correlated with BCVA and pERG in this cohort representing different stages of the disease. These parameters could represent reliable biomarkers in therapeutic clinical trials on USH.