Progression: things we need to remember but often forget to think about.

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.