Luminance-Controlled Pupil Size Affects Landolt C Task Performance

Abstract

Subjects judged the orientation of a 2 min. gap Landolt C located at a distance of 2.4 m. The stimuli were presented in central vision on a CRT, at low to medium contrast. The effects of varying the spectrum and luminance of surround lighting were assessed on both pupil size (measured using infrared pupillometry during task performance) and task accuracy. The task display was protected from the surround lighting, so that its luminance and contrast could be varied independently of the changes in the surround lighting. Indirect surround illumination was provided by . either two illuminants of very different scotopic spectral content but with the same · photopic luminance (Experiment 1 and 3 each), or by using the same illuminant at two different luminance levels (Experiment 2). In experiment 3, the effect of changing surround spectrum was compared to the effect of varying task background luminance between 12 cd/m2 and 73 cdfm2. In all experiments, scotopically enhanced surround lighting produced pupil areas which were reduced by almost 50% in comparison with surround lighting with relatively less scotopic luminance.Concomitantly there was improvement in Landolt C task performance with the scotopically enhanced surround lighting at all contrast and luminance levels. In these experiments, smaller pupil sizes were associated with significantly better visual-task performance in spite of lower task retinal illuminance when compared to the condition with larger pupils. These results suggest that changes in surround spectrum can compensate for the effect on task performance of a reduction in task luminance and supports the possibility that lighting energy savings can accrue in the workplace by shifting lamp spectra to obtain greater scotopic efficacy.

Estimates of Improved Productivity and Health from Better Indoor Environments

“…As an example, in one visual test subjects must identify the location of an open section in a circle (called a Landolt C) that is briefly shown on a computer monitor. Many of these studies have identified statistically significant differences in people's performance on these visual tests with changes in lighting (e.g., Berman et al, 1993Berman et al, ,1994NEMA, 1989); however, the relationship between performance in these visually demanding laboratory tests and performance in typical work (e.g., office work) remains unclear.…”

“…However, based on the published literature (Boray et al, 1989;Veitch et al, 1991;NEMA, 1989) there seems to be no strong or consistent scientific evidence of benefits of full spectrum lighting. Berman et al, (1993; have found that changes in the spectrum of light (with illuminance unchanged) influence both pupil size and performance in visual tests. They suggest that the smaller pupil size when light is rich in the blue-green portion of the spectrum reduced the adverse effects of optical aberrations.…”

A critical examination of perceptual and cognitive effects attributed to full-spectrum fluorescent lighting

“…Krtilova and Matousek (1980), summarising studies of mental workload, visual acuity and visual comfort in relation to lamp type, stated that "statistical evaluation of control tests shows best result for daylight, Daylight fluorescent [CCT=6500K, probably a FSFL] and discharge RVLX lamps" (p. 231), although they provided no detailed data. Berman, Fein, Jewett, and Ashford (1993) compared the effects of varying spectral composition and luminance (photometric brightness) on the performance of the Landolt ring task by 18-45-year-old participants who experienced all luminous conditions. Variations in spectral composition were achieved by varying the combinations of fluorescent lamps that provided the light around the task (the surround), which was presented on a computer screen.…”

Lighting Quality Contributions from Biopsychological Processes

“…44 The two SPD conditions were created by using either three red and one pink lamp, or, in the other condition, one green-blue lamp (the "scotopically enriched" lamp). Pupil size was smaller, and visual performance was greater, for the blue-green lamp than for the red/pink combination, which is consistent with the theory.…”