The relationship between the AdaptDx rod intercept and self-reported visual problems under low luminance.

Background: The AdaptDx has been developed as a clinically friendly instrument for the quantification of rod-mediated performance using a single parameter referred to as the rod intercept. The aim of this study was to determine if the rod intercept is associated with subjective perception of vision under low luminance conditions. Methods: 30 healthy individuals and 26 individuals with varying degrees of age-related macular degeneration completed a validated Low-Luminance questionnaire (LLQ). The 32-item questionnaire has 6 subscales covering general dim lighting, extreme lighting, driving, emotional distress, mobility and peripheral vision. The rod intercept, which is the time taken from photobleaching to when sensitivity recovers to a criterion light level (5x10-3 scotopic cd/m2) where it is completely rod- mediated, was measured for each individual on the Maculogix AdaptDx. Results: Scores on the LLQ were significantly lower in those with AMD compared to the normal subjects for general dim lighting, extreme lighting, driving and emotional distress (p<0.05 for all). The rod intercept was significantly higher in those with AMD (mean = 33.3 minutes) compared to the normals (mean =10.5 minutes; t=-9.525, p=<0.01). There was a statistically significant correlation (Pearson) between the rod intercept and extreme lighting, general dim lighting, driving and emotional distress (p<0.05 for all). Conclusions: Subjective perception of vision under a variety of low luminance conditions is significantly worse in AMD patients compared to healthy individuals. The rod-intercept value on the AdaptDx shows a good association with individual perception of self-reported visual problems under low luminance and at night, further validating its potential clinical use.