Glaucoma is a progressive optic neuropathy. Hence, most glaucomatous eyes demonstrate signs of deterioration over time despite what may appear to be adequate treatment. The main goal of glaucoma treatment is to slow the rate of disease so that patients can prolong their functional vision. Therefore, it is important for clinicians caring for patients with glaucoma to be able to estimate rates of change with structural and functional outcomes in their patients. Various trend analysis models have been previously used to estimate rates of decay in glaucoma. The authors discuss the relevant issues and the inherent caveats related to estimating structural and functional rates of change in glaucoma. Patterns of deterioration, testing frequency, and combing structural and functional rates of change are also addressed.