Development and Validation of the Assessment of Low Luminance Vision-Related Activities.

Initial analysis of the 17-task ALLVA led to removal of one item, walking a mobility course, due to infit and outfit mean square statistics being outside the acceptable range.

For the remaining 16 tasks, item difficulty was well targeted to person ability, with only a minor floor effect.

Clinical vision measures were significantly correlated with person measures.

Bland-Altman analysis indicated a mean difference between test and retest person measures of -0.08 logits (95% limits of agreement 2.16 to -2.32 logits).