Variability of stimulus detection, form discrimination, and color recognition with suprathreshold campimetry in brain-damaged patients

Abstract

This study was performed to assess the reliability of a new method of suprathreshold stimulus detection campimetry and color and form campimetry, and especially to analyze learning effects in the application of these methods. A total of 27 patients (mean age 53.2±17.7 years) with postchiasmatic damage of the visual system were examined on five different occasions with computer-based campimetric tests of suprathreshold stimulus detection (PeriMa), form recognition (Peri-Form), and color discrimination (PeriColor). Either 250 or 500 stimuli were presented on a 17? CRT monitor to achieve high-resolution campimetry in the central visual field (±21.5° vertical and ±27° horizontal eccentricity). Average correlations of the number of detected/correctly recognized stimuli in five consecutive measurements ranged from r=0.86 to r=0.94. As a measure of the variability of visual field size, the individual standard deviation of the five results of each test was taken (stimulus detection: ±4.2%, form recognition: ±6.2%, color recognition: ±6.4%). A measurement of horizontal distances between the vertical meridian and the border of the defective area at the positions of upper/lower 20°, upper/lower 10° and 0°, showed average individual standard deviations between ±1.9° and ±2.9° of visual angle. Correlations between visual field variability and (a) physical health and subjective mental condition, (b) patient’s age, (c) sustained attention, (d) size of defective field, and (e) cause of lesion were small and not significant. We found a learning effect from the first to the fifth measurement, defined as the average increase of detected/correctly recognized stimuli, amounting to 3.1% (stimulus detection), 3.0% (form recognition), and 9.0% (color discrimination, all). To achieve homogeneity of variances and to reduce the influence of the size of the defective field, we used the standard deviation from the individual mean (as 100%) of each patient for further statistical analyses. After this transformation, average deviations from the individual mean of detected/correctly recognized stimuli of each patient were considerably increased: ±9.7% (PeriMa), ±13.8% (PeriForm), and ±12.4% (PeriColor). ANOVA showed significant learning effects. An investigation of horizontal distances from the vertical meridian showed learning effects especially in Periform (+1.7°) and in Pericolor (+2.8°).