A study comparing drivers’ ability to see pedestrians with and without yellow-lens night-driving glasses has found there is no evidence to support claims that they improve night-time road visibility. This goes against advice given by eye care professionals who suggest yellow-lens night-driving glasses to offset the effects of oncoming headlight glare (HLG) that impairs drivers’ abilities to see pedestrians at night.
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Published in JAMA Ophthalmology, the study by Alex D. Hwang and fellow researchers states it would “measure the association between yellow-lens glasses and the detection of pedestrians with and without an oncoming HLG” using driving simulators with an HLG simulator.
Between September 2016 and October 2017, 22 people took part in the study at the Schepens Eye Research Institute. Participants were asked to drive scripted night-driving scenarios three times over, using three different types of yellow-lens glasses and once with clear-lens glasses.
Eight different conditions were used for each participant, with some driving simulations not including the HLG simulator. They were measured on their response to pedestrians wearing different colored shirts.
Over the years, two things have happened that make night driving increasingly difficult for me: I have grown old and automobile headlights have grown whiter and brighter. With the transition from kerosene carriage lamps to sealed beam incandescent and, more recently, high-intensity discharge and light-emitting diode (LED) headlamps, the color and brightness of headlights have gradually evolved […] to a light as harsh, glaring, and painful as the sun is to me.”
Robert W. Massof, PhD
The study found that, when compared to clear-lens glasses, no yellow-lens glasses improved response times to pedestrians when drivers were faced with oncoming headlight glare. Results suggested that older participants displayed slower reaction times when using yellow-lens glasses in simulations where they were not confronted with HLG.
When Massof dug into the results in an effort to determine why yellow lenses did not seem to have an effect on night-driving visibility, which the study did not investigate, he concluded that filtering in all three of the types of lenses was too weak to have a “meaningful association” with visual performance. In short, the lenses are not yellow enough to show an appreciable effect on night-time visibility.
He investigated the results by measuring the amount of light reaching the retina and the glare effects on rods. He found that glare was reduced by 0.22 log unit for the first pair of night-vision glasses, 0.36 for the second pair, and 0.37 for the third pair.
He likens the highest reduction in glare, 0.37 log units, to “reducing glare from a 10,000 cd/m2 headlamp to that from a 4,200 cd/m2 headlamp.”
Massof concludes his analysis of Hwang’s study by stating:
The most interesting finding of Hwang et al. is the magnitude of the adverse association of headlight glare with older people.
Not only are the retinal rod responses saturated by headlights pumping out excess energy in the rods’ preferred part of the spectrum, but rods, cones, and melanopsin in ganglion cells drive pupil constriction, which when combined with nuclear or posterior subcapsular cataract, can further exacerbate the disabling glare and discomfort.”
The study is subject to some limitations, such as the small study group size, and more research is needed to both understand why yellow-lens glasses do not seem to improve night-time vision in older populations in particular.
Hwang AD, Tuccar-Burak M, Peli E. Comparison of Pedestrian Detection With and Without Yellow-Lens Glasses During Simulated Night Driving With and Without Headlight Glare. JAMA Ophthalmol. Published online August 01, 2019. doi:10.1001/jamaophthalmol.2019.2893