LONG-TERM AND SHORT-TERM VARIABILITY OF AUTOMATED PERIMETRY RESULTS IN PATIENTS WITH OPTIC NEURITIS AND HEALTHY-SUBJECTS

Objective: To measure the short-and long-term variability of automated perimetry in patients with optic neuritis and normal subjects. Design : Prospective case-control design of patients with recovered optic neu ritis with intraday and interday repetitions to obtain robust variabil ity measurements. Entry criteria included a corrected pattern SD that was worse than the normal 5% probability level and a mean deviation wo rse than -3 dB but better than -20 dB. Five Humphrey 30-2 full thresho ld tests were administered during a 7-hour period (I test every 2 hour s) on the same day and at the same periods on 5 separate days. Subject s: Seventeen patients with recovered optic neuritis and 10 healthy sub jects of similar age. Main Outcome Measures: Short-term variability an d long-term variability for global visual field data. Results: Patient s with optic neuritis demonstrated variations in visual field sensitiv ity that were outside the entire range of variability for normal contr ols. These variations occurred for multiple tests performed on the sam e day at specific times and for tests performed at specific times on d ifferent days. There were no consistent patterns of sensitivity change s that could be attributed to time of day. The most dramatic fluctuati ons occurred in a patient whose visual fields varied from normal to a hemianopic defect from one week to another and from a partial quadrant loss to a hemianopic defect at different times on the same day. Seven of the patients with optic neuritis also demonstrated intermittent ve rtical step defects. Conclusions: Patients with resolved optic neuriti s can have large variations in visual field results on different days and at different times on the same day. The variations affect both the severity and the pattern of visual field loss and do not appear to be consistent across patients. These data indicate that case must be tak en when automated visual field results in patients with optic neuritis are interpreted. Distinguishing systematic changes in sensitivity fro m variability requires more than a comparison of the current visual fi eld with the most recent previous visual field.