Variability and fatigue effects for automated perimetry in optic neuritis patients

Purpose: To determine the variability of visual field determinations in optic neuritis patients as a function of fatigue and time of day, and to compare these findings with the results for age-matched normal control subjects. Methods: At both the University of Iowa and the University of California, Davis, 10 patients with recovered optic neuritis (ON) and/or multiple sclerosis (MS) were enrolled in the study. Patients had of have an MD and CPSD that was beyond the normal 5% probability level, but no worse than a -15 dB MD value. Five Humphrey 30-2 threshold tests were administered over a 7 hour time period on the same day to examine fatigue effects and at the same times on separate days to examine time of day effects. Results: The majority of ON and MS patients demonstrated variations in visual field results that were beyond the entire : ange of variability for normal control subjects. These variations occurred for multiple tests performed on the same day at various times, and for tests performed at various times on different days. There were no consistent patterns of visual field sensitivity changes demonstrated by all ON and MS patients that were associated with fatigue or with various times of the day. The most dramatic variation occurred in a patient whose visual fields varied from a normal visual field to a hemianopic defect from one day to another. A number of the ON and MS patients also demonstrated vertical steps. Discussion: ON and MS patients can demonstrate large variations in visual field properties on different days and at different times during the same day. These large variations do not exhibit the same pattern from one patient to another. However, the variations affect both the severity and pattern of field loss, thereby influencing the diagnostic interpretation of visual field results.