Functional Vision in Patients With Biallelic USH2A Variants

Purpose: To describe functional vision (FV) and investigate the relationship between FV, visual acuity (VA), and hill of vision (V_TOT) at baseline in patients with biallelic USH2A variants.

Design: Multicenter, international, cross-sectional study.

Methods: In individuals with biallelic disease-causing variants in USH2A, clinical diagnosis of Usher syndrome type 2 (USH2) or autosomal recessive nonsyndromic retinitis pigmentosa (ARRP) was based on history of hearing loss and audiology examinations. The VALVVFQ-48 was administered verbally to participants ≥18 years old. VA was measured in both eyes; V_TOT was determined from static perimetry in the study eye (better VA). FV scores were calculated using Rasch analysis.

Results: Median age of 121 participants (76 with USH2, 45 with ARRP) was 41 years (range: 19-80); 54% were female. FV scores varied from -2.0 to 7.6 logits (median [interquartile range (IQR)]: 2.8 [1.5-3.8]). ARRP and USH2 participants had similar FV scores, both before [mean (95% CI): 2.8 (2.3-3.4) and 2.7 (2.3-3.2), respectively], and after [mean (95% CI): 2.5 (2.1-3.0) and 2.9 (2.6-3.3), respectively; P = .24] adjusting for age, VA, disease duration, and V_TOT. VA and V_TOT accounted for 29% and 26% of the variance in FV scores, respectively (P < .001 for each). Together, they accounted for 36% of variance observed.

Conclusions: Biallelic USH2A variants were associated with a large range of FV, yet similar in ARRP and USH2, despite hearing loss in USH2. The modified VALVVFQ-48 we evaluated is not ideal for detecting the impact of USH2A-associated retinal degenerations on activities of daily living.