Pupillary Size Differences under Incandescent and High-Pressure Sodium Lamps

In the absence of a color-discrimination requirement, it is common in the fields of illuminating engineering and lighting design to consider that two lighting systems with an equal photopic illuminance level and equal spatial distribution are essentially equivalent. Differences in spectral power distribution associated with different lighting technologies are presumed not to affect visual performances when the task is achromatic. Thus, lighting systems with different spectral power distributions are often considered equally valid for general and task lighting, as shown by the common usage of incandescent, fluorescent, and high-pressure sodium lighting for similar applications. The decision of choosing one lighting system over another is then determined by criteria other than spectral power distribution. This practice is based on the assumption that the CIE luminous efficiency function adequately describes visual function under common lighting conditions.

As part of a continuing joint program between Lawrence Berkeley Laboratory and University of California, San Francisco to study human responses to electric lighting, we report here that significant difference in pupil size occur when subjects are exposed to indirect high-pressure sodium (HPS) as compared with indirect incandescent lighting when the light intensities are photopically matched.