Eyeworld

145 EW RETINA April 2016 of those with central scotomas are longer than for normally sighted people," she said. "If people have a scotoma that is to the left or to the right, there is a marked increase in response time to pedestrians on the corresponding side." Even those who have a central blind area above or below the position of gaze can run into trouble if their gaze is even momentarily averted in a direction that obscures a potential hazard from view. "To our knowledge, this is the first time that this has been systematically investigated," Dr. Bowers said. While it would be possible to potentially compensate for the scotoma by scanning from side to side, elevated response times here suggest that drivers are in fact looking straight ahead most of the time, she said. From a clinical perspective, the study indicates that licensing authorities should take into account large scotomas in the central visual field as some countries already do. "The people who we tested here would not have been permitted to drive in the U.K.," Dr. Bowers said. Yet, 6 of the drivers retained their U.S. licenses and 1 had relinquished the privilege within the last 2 years. Dr. Bowers hopes that practi- tioners seeing patients with AMD will take into account the size and the density of the scotoma when advising them to continue driving or not. "Physicians should make patients aware that they have this blind area in their vision and that it potentially means that they might not see something," she said. Going forward, Dr. Bowers would like to see a larger follow-up study done on this. EW References 1. Bronstad PM, et al. Driving with central visual field loss II: how scotomas above or below the preferred retinal locus (PRL) affect hazard detection in a driving simulator. PLoS One. 2015 Sep 2;10(9):e0136517. 2. Bronstad PM, et al. Driving with central field loss I: effect of central scotomas on responses to hazards. JAMA Ophthalmol. 2013;131(3):303–309. Editors' note: Dr. Bowers has no finan- cial interests related to her comments. Contact information Bowers: alex_bowers@meei.harvard.edu Participants were asked to spend 2 sessions in the simulator, each in- volving about 1 hour of test drives, Dr. Bowers noted, adding that every participant was first given time to get used to the simulated driving conditions. "Across both driving simulator sessions, there would be a total of more than 100 pedestrians," she said. "They were programmed so that if it had been in the real world, there would have been a collision if the person kept driving at the same speed without taking any evasive action." However, to avoid subject- ing participants to what would have been a lot of collisions, investigators programmed the pedestrians to stop before they entered the travel lanes. "Whenever drivers saw one of these pedestrians, they had to respond by pressing the horn. From that we were able to measure detection rates and their reaction time," Dr. Bowers said. Results from the first study in- dicated that when the patients' sco- tomas were to the left or to the right of their gaze point and a pedestrian stepped off the curb in that area, the response time to pressing the horn was slow. "They had very long response times," Dr. Bowers said. "In most cases, they would have seen the pedestrian so late that they wouldn't have been able to stop." Response times to pedestrians not in the area of visual field loss were delayed relative to normally sighted controls but were not as delayed as those involving the area of the scotoma, she reported. Key findings With this in mind, in the latest study involving central scotomas, investigators expected that subjects who had a blind area above their gaze point might be a little slower to react than controls but that this would not affect their ability to detect pedestrians. "We didn't think that we would find any effect of the scotoma," she said, but investigators found that response times were ele- vated in some instances. This, they determined, only occurred when the scotoma obscured the driver's view of the pedestrian, which was an issue at times when some glanced down toward the speedometer or something else. "Across these 2 studies, the key finding is that response times

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