People with central vision loss can judge the motion of vehicles almost as accurately as people with normal vision, a new international study shows. Despite age-related macular degeneration (AMD), they estimated the moment when an approaching car would reach them with comparable accuracy as a group with normal vision. These are the findings of new research conducted by Johannes Gutenberg University Mainz (JGU) in collaboration with Rice University in Texas, USA, and other American as well as French researchers. Their research, recently published in the open-access journal
PLOS One, compared older adults with AMD to a control group with normal vision in virtual-reality traffic scenarios.
The new study built on earlier work of the authors that investigated arrival time judgments in normally sighted participants using virtual-reality methods. This time, the team wanted to understand whether people with impaired vision rely more heavily on sound and whether having both sight and sound provides an advantage compared to having vision alone. "There are few studies that look specifically at collision judgments in people with visual impairments," explained Professor Patricia DeLucia, perceptual and human factors psychologist from Rice University. "Even though tasks like crossing a street or navigating busy environments depend on this ability."
Decisions based on vision and sound
The study's experimental design used a virtual roadway scene in which a vehicle approached the observer from a pedestrian's viewpoint. The virtual reality system provided realistic simulations of the vehicle sound, implemented by Daniel Oberfeld-Twistel, Professor of Experimental Psychology at Mainz University. The visual and auditory information were systematically varied: the scene was presented either visually, auditorily, or with both modalities available simultaneously. The participants were then asked to press a button at the moment they believed the vehicle would have reached them. Using data analysis strategies developed at JGU, the study provides a detailed analysis of the perceptual cues that were associated with participants' arrival time judgments, and examines how features such as optical size, optical expansion, or sound intensity contributed to their estimates.
"Thanks to our advanced audiovisual simulation system and customized data analysis, we gained an almost microscopic insight into how pedestrians use auditory and visual information to estimate the arrival time of an approaching vehicle," said Professor Daniel Oberfeld-Twistel. "This goes beyond what we knew from previous studies."
Surprisingly, the group with AMD in both eyes performed very similarly to the group who had normal vision when estimating the time the vehicle would reach them. The team observed that, under purely visual conditions, older adults with AMD tended to rely somewhat more on pictorial or heuristic cues – such as the apparent size of the vehicle – compared to normally sighted participants. However, when both visual and auditory information were available, the two groups still showed comparable accuracy, and there was no clear advantage of combining sight and sound over vision alone.
No evidence for safe navigation in real traffic
"Our results indicate that even reduced central vision still provides useful information for judging approaching objects," explained Oberfeld-Twistel. "People with age-related macular degeneration continue to benefit from their residual vision instead of relying solely on auditory cues." He pointed out, however, that the study used deliberately simplified virtual-reality scenes with just a single approaching vehicle.
"Future work will therefore need to examine whether the findings hold in more complex environments, for example with multiple vehicles or when the vehicles are accelerating," Patricia DeLucia added. Such research could help guide developments in mobility, rehabilitation, and traffic safety.
In addition to Johannes Gutenberg University Mainz and Rice University, the research team included collaborators from the University of Iowa, Lamar University, Retina Consultants of Texas, the Davies Institute for Speech and Hearing, and the University of Toulouse. This work was supported by the National Eye Institute of the National Institutes of Health under award number R01EY030961. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
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