The pupillary response to color and luminance variant multifocal stimuli.

PURPOSE: We are developing multifocal pupillographic objective perimetry (mfPOP) to assess localized changes in function within visual pathways. In this study, we investigate novel mfPOP stimuli designed to target neural components from either or both the sub-cortical pupillary luminance response and the cortically driven color response.
METHODS: Pupillary responses of 12 subjects were recorded to eight mfPOP stimulus variants (protocols). Forty-eight visual field test-regions (24/eye) were stimulated concurrently with uncorrelated sequences of either high or low luminance-contrast, luminance- plus color-contrast, or equiluminant color-exchange stimuli. Stimulus pulses were of 50 ms duration and were presented at mean intervals of 4 seconds/region. Test durations were 4 or 8 minutes; therefore, estimated responses were derived from 60 or 120 stimulus presentations to each test region.
RESULTS: Pupillary response amplitudes were more influenced by luminance-contrast than the color-contrast of stimuli; response delays, however, were more closely linked to the proportion of color- versus luminance-contrast in each protocol. Significant differences (P < 0.05) in amplitudes but not delays were present between all three high luminance-contrast protocols and a low luminance-contrast luminance protocol, regardless of color content. The reverse pattern was observed between the equiluminant color exchange protocol and this same low luminance-contrast luminance protocol. Only the low luminance-contrast plus color exchange protocol differed significantly from the low luminance-contrast luminance protocol in both measures.
CONCLUSIONS: Two protocols, utilizing low and high luminance-contrast plus color exchange, were identified as likely to incorporate both cortical and subcortical response components, and were deemed potential candidates for further investigation in clinical studies.