Effect of environmental luminance on contrast sensitivity in vehicle drivers.

Abstract

PURPOSE: To evaluate the effect of the luminance of the environment on contrast sensitivity (CS) in vehicle drivers. METHODS: CS was determined under photopic (100cd/m2) and mesopic (3cd/m2) conditions in 103 subjects (night eye) using the OPTEC 3500 instrument and the FACT test (for spatial frequencies of 1.5,3,6,12,18 cycles/º. Both photopic and mesopic CS were evaluated after a 5 min period of dark adaptation. RESULTS: Maximum photopic and mesopic CS values were recorded for a spatial frequency of 6 cycles/º. Under both luminance conditions, significant differences in CS were observed according to subject age and whether they had undergone cataract surgery CS diferences between the two levels of luminance were noted for all spatial frequencies expect 3 cycles/º CONCLUSION: Photopic and mesopic CS are both-pass functions. Age shows a negative effect on mesopic and photopic CS. Higher driving frequencies were related to improved photopic CS for intermediate stimuli but these did not affect mesopic CS. Cataract surgery led to improved CS for intermediate spatial frequencies at both luminance levels. A reduced ambient luminance negatively affects CS in non-operated eyes.