Detecting progression, and estimating the rate of change, are among the most important challenges in the care of patients with glaucoma. With rapidly developing technology, there is a need to rethink what we mean to measure, why we measure it, and how we think about these measurements and how they relate to the disease. This article outlines, informally, a small number of issues that may be important to clinicians and researchers alike but are not often discussed in the literature. It is intended to be useful as a highly selective minireview of recent work and a stimulus for future research. It is organized under three main headings that sum up the main message of each section.