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

This study was performed to assess the reliability of a new method of supra threshold 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 (Peri Ma), form recognition (PeriForm), and color discrimination (PeriColor). Eit her 250 or 500 stimuli were presented on a 17" CRT monitor to achieve high- resolution campimetry in the central visual field (+/-21.5 degrees vertical and +/-27 degrees horizontal eccentricity). Average correlations of the nu mber of detected/correctly recognized stimuli in five consecutive measureme nts ranged from r=o.86 to r=o.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%, col or 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 degrees, upper/lower 10 degrees and 0 degrees, showed avera ge individual standard deviations between +/-1.9 degrees and +/-2.9 degrees of visual angle. Correlations between visual field variability and (a) phy sical health and subjective mental condition, (b) patient's age, (c) sustai ned attention, (d) size of defective field, and (e) cause of lesion were sm all and not significant. We found a learning effect from the first to the f ifth measurement, defined as the average increase of detected/correctly rec ognized stimuli, amounting to 3.1% (stimulus detection), 3.0% (form recogni tion), and 9.0% (color discrimination, all). To achieve homogeneity of vari ances and to reduce the influence of the size of the defective field, we us ed the standard deviation from the individual mean (as 100%) of each patien t for further statistical analyses. After this transformation, average devi ations from the individual mean of detected/ correctly recognized stimuli o f each patient were considerably increased: +/-9.7% (PeriMa), +/-13.8% (Per iForm), and +/-12.4% (PeriColor). ANOVA showed significant learning effects . An investigation of horizontal distances from the vertical meridian showe d learning effects especially in Periform (+1.7 degrees) and in Pericolor ( +2.8 degrees).