Baseline visual fields in the RUSH2A study: Associated factors and correlation with measures of disease severity

Abstract

Purpose : To address limited data characterizing retinal degeneration related to disease-causing sequence variants in USH2A, the Foundation Fighting Blindness Consortium is conducting a 4-year multicenter, international natural history study: Rate of Progression in USH2A-related Retinal Degeneration (RUSH2A). We report baseline data on visual field testing (including reproducibility) and its relationship with baseline characteristics and other functional and structural measures.

Methods : Intra-class coefficients (ICC) were used to assess reproducibility of triplicate full-field static perimetry (SP) and between-eye symmetry of seeing areas of kinetic perimetry (KP). General linear models were used to assess the association of demographic and clinical characteristics with total hill of vision (V_TOT, decibel-steradians) derived from SP. Association between V_TOT and other measures (including KP seeing area (deg²), visual acuity (VA), macular sensitivity on fundus-guided microperimetry, ERG amplitudes and latencies, and SD-OCT measures of central subfield thickness (CST) within the center 1mm and presence of intraretinal cysts) was assessed using Spearman correlation coefficients and t-tests.

Results : Participants with Usher syndrome type 2 (N=80) had more severe visual field loss (determined by V_TOT) than those with non-syndromic retinitis pigmentosa (RP) (N=47) (22.5 ± 21.5 vs 37.1 ± 24.7, P=.002, adjusting for duration of disease and age of vision loss onset). No other baseline characteristics were associated with mean V_TOT. Mean V_TOT measures among 3 repeat tests were 32.7 ± 24.1, 31.2 ± 23.4, and 31.7 ± 23.9 (ICC = .97). Better VA, higher photopic ERG 30Hz flicker amplitudes, higher mean sensitivity, higher CST, absence of macular cysts, and higher III4e seeing area were associated with higher V_TOT (all r > .48; all P <.05). Mean KP III4e isopter areas for left (4561 ± 4426) and right eyes (4136 ±4249) were concordant (ICC=.92).

Conclusions : After adjusting for duration of disease and age of onset, participants with USH2A-related Usher syndrome had more severe visual field loss than with USH2A-related non-syndromic RP. The volumetric measure of V_TOT was highly reproducible and strongly correlated with other functional and structural metrics, suggesting it may be a good summary measure of disease severity in patients with USH2A-related retinal degeneration.

This is a 2020 ARVO Annual Meeting abstract.