The measurement of contrast sensitivity is taught on undergraduate optometry courses, yet few practitioners routinely use contrast sensitivity tests in practice (Latham 1998). Contrast sensitivity measurement can be of benefit in many areas of optometric practice, including the diagnosis of ocular disease (Arden 1979), contact lens fitting (Bradley et al. 1993) and in patients who have difficulty following refractive surgery (Perez-Santonja et al. 1998). This article provides evidence for the importance of measuring contrast sensitivity specifically in patients with low vision. It will discuss the contrast sensitivity function, the Pelli–Robson chart (the most common method of clinically measuring contrast sensitivity) and the relevance of this measurement for everyday tasks. Finally, mechanisms for improving contrast will be mentioned.