PURPOSE. We have previously used measurement of eccentric chromatic contrast sensitivity in patients with glaucoma to documented modest (6-9 dB) improvements in visual function following glaucoma surgery (Fellman et al., American Academy of Ophthalmology, 1999). However, the size and complexity of the xenon-arc-based apparatus made this system impractical for routine clinical use. Therefore we have developed a small, inexpensive clinical testing station for measuring eccentric chromatic contrast sensitivity. METHOD. An iMac computer, mounted on an examining chair, was calibrated and programmed to produce stimuli modulated from equal-energy white along three cardinal directions in color space: equiluminant red-green and tritan axes, and the luminance axis. Stimuli were 500 msec pulses presented at five locations: at the fovea and at 12° eccentricity along the four diagonal meridia. The stimuli were squares, 0.6° on a side in the fovea and 3° on a side at the eccentric locations. Subjects were tested twice, in sessions one week apart, to assess test-retest variability.
RESULTS. Test-retest variability in patients and normal subjects was similar to that obtained with the xenon-arc-based system, with 99% confidence limits for test-retest variability less than 6 dB. Patient acceptance was good, with testing time typically less than 5 minutes. Blind-spot testing showed that the stimulus configuration encouraged proper fixation. Decrease in stimulus duration fro 500 msec to 50 msec had little effect on luminance sensitivity and a dramatic effect on chromatic sensitivity, showing that chromatic channels were successfully isolated.
CONCLUSIONS. Low test-retest variability makes this system suitable for detecting modest changes function in response to treatment for glaucoma