The Effect of Automobile Window Tints on Contrast Sensitivity and Color Discrmmination Under Photopic and Mesopic Conditions.

Background: The objective of this study is to determine if tinted windshields and windows impact the contrast sensitivity function (CSF) and color vision in drivers under Photopic (high luminance) and Mesopic (lower luminance) conditions. Methods: A sample of subjects (N=21) in the age range 21-30 years with good visual acuity and no known history of color vision defects were included. The Vistech Contrast Sensitivity Chart and Hardy Rand Rittler (HRR) Color Vision tests were used to measure subject Contrast Sensitivity and Color Vision, respectively. Measurements were made through filters that closely approximate the transmittance levels of commercial automobile windshields and windows. Measurements were repeated under mesopic light levels. Mesopic conditions were simulated by using neutral density filters of 1.0 log units. Analysis & Results: Contrast sensitivity data were plotted as a function of the following spatial frequencies 1.5, 3.0, 6, 12, and 18 cycles per degree for three tint densities and a baseline condition under photopic and a simulated mesopic condition. Under mesopic conditions, there was a significant drop in contrast sensitivity across all spatial frequencies. Under photopic conditions, there was a drop in contrast for the higher spatial frequencies. Results from this pilot study could have potential implications for optometrists and other eye care providers that are solicited by patients for letters that permit the use of tinted windows as a medical necessity.