Poster Session I: Measuring luminance CSFs from the fovea to far peripheries.

Abstract

We measured luminance contrast thresholds for three subjects in the visual field of the left eye up to 56, 49, 84, and 63 degrees in nasal, superior, temporal, and inferior directions, respectively. The stimulus was a cosine-Gabor of 10 deg diameter. The stimulus size was constant for all eccentricities. The average luminance of the background was 31cd/m2. The stimulus duration was 0.5sec with 0.5sec increasing and decreasing temporal slopes. The thresholds were measured with the psi procedure of two temporal alternative forced choice. The results showed that although at small eccentricities no significant differences in thresholds were found among directions, the differences were prominent at large eccentricities beyond 40 degrees in all frequencies. Most previous peripheral CSFs were based on data measured within certain ranges of eccentricity, and extrapolated outside these ranges. We optimized the parameters of the previous CSFs using the present results within these limited ranges, and confirmed that the previous CSFs fitted the present results. Then, we applied the present results in all eccentricities to the previous CSFs. It was found that the previous CSFs tended to be higher than the present results beyond 60 degrees in temporal and beyond 40 degrees in other directions in all frequencies. This would indicate that the previous CSFs at large eccentricities were not correctly inferred by extrapolation using data measured at small eccentricities.