In the current study, Diniz-Filho and colleagues1 report on an important and practical issue for clinicians who care for patients with glaucoma, namely, trying to determine the influence of cognitive decline on perimetric testing. Specifically, they hypothesized that cognitive decline was associated with increased visual field (VF) variability, a finding that could lead to delayed or false detection of disease occurrence and progression. The effect of cognitive decline on glaucoma testing is important to understand, as the prevalence of both conditions increases with age.2,3 In the Salisbury Eye Evaluation,2 the prevalence of glaucoma among white individuals increased from 3.4% at age 73 to 74 years to 9.4% among those 75 years and older; the increase in prevalence among black individuals was even greater, with glaucoma affecting 5.7% of 73- to 74-year-olds and 23.2% of those 75 years and older. Cognitive impairment follows a similar age-related pattern in the United States, with 16.0% of those 71 to 79 years old and 29.2% of those 80 to 89 years old affected.3