Contrast sensitivity during night driving in subjects over 50 years.

Abstract

PURPOSE: To evaluate contrast sensitivity (CS) in mesopic conditions in the presence and absence of glare in vehicle drivers over the age of 50 years. METHODS: Mesopic CS (3cd/m2) was determined in 120 subjects (right eye) using the OPTEC 3600 device and the FACT test. This involved evaluating the contrast threshold for the spatial frequencies 1.5,3,6,12 and 18 cycles/º. All test were performed with habitual correction for long distance. Contrast sensitivity measurements with and without glare were made after a 5 min period of dark adaptation. RESULTS: Maximum mesopic CT values with and without glare were obteined for the spatial frequencies 6 and 12 cycles/º mesopic CS decreasing for higher or lower frequencies. Mesopic CS also dismished with age (p<0.03). Hiher mesopic CS values were recorded for heavy vehicle drivers than motorcar drivers (p<0.05) and for subjects driving more than 5 days per week (p<0.05). CONCLUSION: The mesopic CS function shows a band pass pattern similar to that shown by the photopic CT function. The higher mesopic CS in heavy vehicle drivers could reflect the visual requirements upheld by Spanish legislation. The fact that subjects with less mesopic CS drive less than 5 days/weeks suggests they are more reluctant to drive since they feel more insecure. The OPTEC 3500 instrument does not have an effective source of glare that is capable of producing disability glare.