Correlation of multi-luminance mobility testing with visual function tests in a phase 3 trial of voretigene neparvovec for biallelic RPE65-mediated inherited retinal disease

Abstract

Purpose : A phase 3 trial of voretigene neparvovec (VN) in biallelic RPE65-mediated inherited retinal disease used a novel multi-luminance mobility test (MLMT) endpoint to measure subjects’ ability to navigate in various light levels. However, MLMT is not available in non-research settings. These post hoc analyses addressed the correlation between change in MLMT performance and change in more common tests of visual function, including full-field light sensitivity threshold (FST), and Humphrey visual field (HVF) foveal sensitivity and macula thresholds.

Methods : Twenty-nine subjects with RPE65 gene mutations received bilateral, subretinal injections of VN in a phase 3 study (randomization 2:1 intervention to control), with control subjects receiving VN after one year. Subjects were tested for accuracy and speed on MLMT at 7 standardized illumination levels from 1 to 400 lux. The lowest level at which subjects could pass MLMT was determined at baseline. The primary endpoint was change in bilateral MLMT score at 1 year. In this analysis, bilateral change score was reported as percentage of maximum possible improvement (%max) from baseline MLMT lux score, reducing the impact of possible ceiling effect on the analysis. Additional endpoints were change in FST, HVF foveal sensitivity, and HVF macula threshold. Each pairing of variables was graphed as a scatterplot; a Pearson correlation coefficient measured the linear relationship between the two variables.

Results : Correlation between MLMT bilateral change score %max and FST was -0.74 (Fig. 1). The correlations between MLMT bilateral change score %max and HVF foveal sensitivity and MLMT bilateral change score %max and HVF macula threshold were 0.66 and 0.63, respectively (each p<0.001).

Conclusions : MLMT showed good correlation with FST, HVF foveal sensitivity, and HVF macula threshold. Improvements in MLMT, FST, and HVF macula threshold testing may indicate a greater retinal sensitivity to lower luminance levels, which may increase independent ambulation and improve ability to conduct activities of daily living in low- or lower-light environments.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Fig. 1. Correlation between change in MT and change in FST