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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 neuritis with intraday and interday repetitions to obtain robust variability measurements. Entry criteria included a corrected pattern SD that was worse than the normal 5% probability level and a mean deviation worse than −3 dB but better than −20 dB. Five Humphrey 30-2 full threshold tests were administered during a 7-hour period (1 test every 2 hours) on the same day and at the same periods on 5 separate days. Subjects: Seventeen patients with recovered optic neuritis and 10 healthy subjects of similar age. Main Outcome Measures: Short-term variability and long-term variability for global visual field data. Results: Patients with optic neuritis demonstrated variations in visual field sensitivity that were outside the entire range of variability for normal controls. These variations occurred for multiple tests performed on the same day at specific times and for tests performed at specific times on different days. There were no consistent patterns of sensitivity changes that could be attributed to time of day. The most dramatic fluctuations 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 vertical step defects. Conclusions: Patients with resolved optic neuritis 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 care must be taken when automated visual field results in patients with optic neuritis are interpreted. Distinguishing systematic changes in sensitivity from variability requires more than a comparison of the current visual field with the most recent previous visual field.

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To investigate the relationship between reaction time (RT), stimulus intensity and visual field eccentricity. We generated frequency of seeing (FOS) curves and measured RTs by testing 10 perimetrically experienced normal subjects with a Humphrey perimeter controlled by a custom program. Subjects were tested from 10 degrees to 50 degrees eccentricity along the nasal horizontal meridian in 10 degrees increments. A range of 20 dB, centered on threshold, was tested in 1 dB steps along with 60 and 0 dB intensities as catch trials. Twenty repetitions for each intensity at each location were used. Linear regression showed a significant increase in suprathreshold RT (to the 0 dB stimulus) with increasing eccentricity. The RT at the calculated FOS 50% threshold was prolonged by about 200 ms compared with the RT using the 0 dB target at the equivalent eccentricities. Also, when the difference between the RT at 0 dB stimulus and the RT at threshold was regressed against visual field eccentricity there was a significant decrease with eccentricity. When the RT(pi) (RT prolongation from threshold relative to the 0 dB stimulus) was plotted as a function of decreasing stimulus attenuation, the results fit the function RT(pi)=a+bi(3) (i=stimulus intensity) with r(2)>0.94 at all eccentricities. However, the slope of the function flattened with increasing eccentricity. Using conventional automated perimetry stimuli in perimetrically experienced young subjects, suprathreshold RT increases but threshold RT prolongation decreases with increasing visual field eccentricity. RT fits a power function with decreasing stimulus attenuation but the slope flattens with eccentricity. This relationship found along the nasal horizontal meridian may allow use of RT to cross-check threshold results or to define response windows for reliability indices of conventional automated perimetry.