Visual fields: Fluctuation and progression

Abstract

The primary obstacle in detecting whether or not a glaucoma patient's visual field loss is progressing is to separate true progression from changes due to variability or fluctuation between tests. Fluctuation is defined as the variability in the response to the same stimulus that is not related to true disease progression. As visual field testing is a subjective examination, variable responses may be obtained each time the test is performed (long-term fluctuation) or even during the same test (short-term fluctuation). This variability has been the biggest drawback of visual field assessment, as variability can greatly confound interpretation of change. Fluctuation varies among patients and among sectors in the same visual field, and usually it increases with severity of disease. To detect true progression, we need to evaluate whether the observed change exceeds the expected fluctuation for a particular area. Many strategies have been developed to deal with this issue and will be reviewed in this chapter. © 2010 Springer-Verlag Berlin Heidelberg.