Xu and colleagues evaluated contrast sensitivity (CS) in a large group of older US adults (65 years or older) to try to determine a clinically relevant threshold for CS associated with self-reported functional visual disability. The latter was considered to be present if people reported blindness or answered yes to having any of the following: difficulty seeing the TV across the room, reading the newspaper, or recognizing someone across the street. Studies such as this are important to help us understand the relevance in people’s lives of outcome thresholds used in routine practice or research studies. Using the Youden Index (a statistical measure that combines sensitivity and specificity into a single value), the investigators found that older adults began to experience self-reported functional visual disability at a threshold of 1.60 log CS, with each 0.1 unit decrease in baseline log CS being independently associated with 12% higher odds of having incident self-reported functional visual disability. The sensitivity and specificity of the 1.60 log CS cutoff point (the level at which CS loss begins to correspond to self-reported functional visual disability) was found to be 67% (95% CI, 62%-71%) and 70% (95% CI, 69%-72%), respectively. However, identifying thresholds such as this is challenging; the study has limitations, which the authors outlined in their article. Because of these limitations, replications of their results are necessary.