Pupillary Size Differences Under Incandescent and High Pressure Sodium Lamps

Eight healthy young adult subjects produced significantly larger steady state pupil areas, as measured by infra-red pupillometry, when exposed to indirect lighting from high frequency high pressure sodium lamps compared to photopically matched levels of indirect incandescent lamps at three levels of luminance: 30, 60 and 90 candelas per meter squared (cd/m²). Three additional intensities were studied, which were not matched photopically between lamps. Analysis of all data showed that a scotopic spectral distribution accounted for pupil size better than either a photopic spectrum or an Alpern-Campbell pupillary response spectrum. Because pupil size can affect visual functioning, these results suggest that control of pupil size should be considered in lighting design and that the scotopic spectral output from lamps should be important in determining the effectiveness of a lighting environment.