Senescent changes of the normal visual field: an age-old problem

Purpose. To examine the effect of normal aging on visual field sensitivity and identify the best-fitting function for normal populations. Methods. Ful l Threshold standard automated perimetry data (program 24-2, Humphrey Field Analyzer) was collated retrospectively from clinically normal subjects who had previously been recruited for studies of normal visual function. One e ye of each subject was randomly selected for analysis. Linear, bilinear, an d simple nonlinear candidate functions of mean sensitivity vs, age (indepen dent variable) were applied to these cross-sectional population data. Diffe rences in the aging effect by eccentricity and hemifield were also consider ed. Results. Data from 562 normal eyes were available for analysis. A signi ficant negative relationship existed between age and mean visual field sens itivity within the cross-sectional population data. Coefficients of determi nation for the linear, bilinear, and nonlinear functions were 0.21, 0.20, a nd 0.26, respectively, indicating that the nonlinear function provided best characterization of the effect of age on mean sensitivity. A small but sig nificant increase in the aging effect was present both peripherally (p < 0. 001) and superiorly (p < 0.001). Discussion. The nonlinear function that pr ovided the best fit to cross-sectional population data indicates that age e xerts an increasing effect on perimetric sensitivity with age, which has im plications for clinical devices that use linear age coefficients to correct for normal aging effects. A linear age correction will overestimate aging changes for younger subjects and, therefore, may miss early pathologic chan ges in visual sensitivity. Conversely, linear age correction will also unde restimate aging changes for older subjects and, thus, may overcall patholog ical sensitivity loss in this group. The effect of age within subjects requ ires further investigation to provide reliable estimates of the effect of a ge on sensitivity.