Objective: To determine the extent of difference between better-eye visual field (VF) mean deviation (MD) and integrated VF (IVF) MD among Salisbury Eye Evaluation (SEE) subjects and a larger group of glaucoma clinic subjects and to assess how those measures relate to objective and subjective measures of ability/performance in SEE subjects. Design: Retrospective analysis of population- and clinic-based samples of adults. Participants: A total of 490 SEE and 7053 glaucoma clinic subjects with VF loss (MD ≤−3 decibels [dB] in at least 1 eye). Methods: Visual field testing was performed in each eye, and IVF MD was calculated. Differences between better-eye and IVF MD were calculated for SEE and clinic-based subjects. In SEE subjects with VF loss, models were constructed to compare the relative impact of better-eye and IVF MD on driving habits, mobility, self-reported vision-related function, and reading speed. Main Outcome Measures: Difference between better-eye and IVF MD and relationship of better-eye and IVF MD with performance measures. Results: The median difference between better-eye and IVF MD was 0.41 dB (interquartile range [IQR], −0.21 to 1.04 dB) and 0.72 dB (IQR, 0.04–1.45 dB) for SEE subjects and clinic-based patients with glaucoma, respectively, with differences of ≥2 dB between the 2 MDs observed in 9% and 18% of the groups, respectively. Among SEE subjects with VF loss, both MDs demonstrated similar associations with multiple ability and performance metrics as judged by the presence/absence of a statistically significant association between the MD and the metric, the magnitude of observed associations (odds ratios, rate ratios, or regression coefficients associated with 5-dB decrements in MD), and the extent of variability in the metric explained by the model (R 2 ). Similar associations of similar magnitude also were noted for the subgroup of subjects with glaucoma and subjects in whom better-eye and IVF MD differed by ≥2 dB. Conclusions: The IVF MD rarely differs from better-eye MD, and similar associations between VF loss and visual disability are obtained using either MD. Unlike better-eye MD, IVF measurements require extra software/calculation. As such, information from studies using better-eye MD can be more easily integrated into clinical decision-making, making better-eye MD a robust and meaningful method for reporting VF loss severity. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. [ABSTRACT FROM AUTHOR]