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Central Visual Field Loss and Driving—Reply

Central Visual Field Loss and Driving—Reply In reply Desapriya and colleagues commented on our use of simulation in evaluating detection performance of drivers with CFL. Although driving assessments using open-road courses have high face validity, such studies are limited by the inability to control whether, when, and where hazards appear.1-4 By comparison, a high-fidelity driving simulator, such as the one used in our study,5 provides a safe, controlled environment in which to conduct much-needed studies to evaluate the effects of different types and levels of vision impairment on driving performance.5-8 Using a driving simulator, we have been able to repeatedly evaluate detection of potential pedestrian hazards under exactly the same conditions for all participants in a manner that is impossible in an on-road study1 (even using a closed-road course). In the prior on-road study of drivers with “mild” central field loss (CFL)3 that Desapriya and colleagues noted, there were only 2 stunt actor appearances per driver compared with 104 pedestrian appearances per participant in our driving simulator study. Our main finding was that participants with CFL had significantly and dangerously longer reaction times to pedestrians who appeared in scotomatous areas than in nonscotomatous areas of their visual field. Our sample size was relatively small; however, the effects we found were large and highly significant owing to our use of a repeated-measures design with multiple presentations of hazards. In our study, participants were aware that we were evaluating their ability to detect pedestrians (and where these pedestrians tended to appear) and may therefore have responded more quickly than they would in real life.9 Thus, our results might even underestimate the risk that central scotomas pose. We agree with Desapriya and colleagues that other factors, besides vision impairment, affect reaction times in older drivers. However, it is unlikely that any such factors affected our results. Our main analysis was a within-subjects comparison of reaction times between scotomatous and nonscotomatous regions of the visual field. Other factors such as cognitive slowing, muscle weakness, or the effects of medications would have affected reaction times in scotomatous and nonscotomatous regions to a similar extent. Desapriya and colleagues wrote, “A surprising finding from this study is that most individuals from the CFL group meet the current restricted driver's licensing requirements in the United States.” That was not a finding of our study; we intentionally set the inclusion criteria to ensure that we recruited individuals with CFL who could legally drive somewhere in the United States, albeit with a restricted license. The fact that such patients are licensed to drive does not mean that they “are operating motor vehicles without realizing that their vision is impaired,” as Desapriya and colleagues wrote. Most such patients and their doctors are well aware of their visual acuity loss. However, patients with CFL are often unaware of their scotoma10 and should be advised about how it might impair their ability to respond to hazards when driving. Indeed, lack of data about the effects of central scotomas on driving performance was the main reason for conducting our study. We agree with Legge9 that, besides the mere presence, the location of the scotoma could be important and that a follow-up study including patients with scotomas above or below the preferred retinal locus is needed; we are completing such a study. Desapriya and colleagues concluded that there is an urgent need for driver's licensing agencies to establish reliable visual function screening tests. While we agree in principle with this statement, the data for such recommendations cannot, unfortunately, be derived from meta-analyses of any existing literature. This was highlighted in the recent Cochrane review by Desapriya et al11 of the effects of vision screening on the prevention of older driver–related crashes, in which they found no studies that even met the inclusion criteria. In fact, we are still a long way from understanding how different types of vision impairment affect specific driving skills and driving safety. Therefore, we need to focus our research efforts on building a strong evidence base for the effects of vision impairment on driving performance, as our recent studies begin to do. Back to top Article Information Correspondence: Dr Bronstad, Schepens Eye Research Institute, 20 Staniford St, Boston, MA 02114 (matthew_bronstad@meei.harvard.edu). Conflict of Interest Disclosures: None reported. References 1. Bowers AR, Tant M, Peli E. A pilot evaluation of on-road detection performance by drivers with hemianopia using oblique peripheral prisms. Stroke Res Treat. 2012;2012:17680623316415PubMedGoogle Scholar 2. Bowers AR, Peli E, Elgin J, McGwin G Jr, Owsley C. On-road driving with moderate visual field loss. Optom Vis Sci. 2005;82(8):657-66716127330PubMedGoogle ScholarCrossref 3. Lamble D, Summala H, Hyvärinen L. Driving performance of drivers with impaired central visual field acuity. Accid Anal Prev. 2002;34(5):711-71612214966PubMedGoogle ScholarCrossref 4. Haymes SA, LeBlanc RP, Nicolela MT, Chiasson LA, Chauhan BC. Glaucoma and on-road driving performance. Invest Ophthalmol Vis Sci. 2008;49(7):3035-304118326696PubMedGoogle ScholarCrossref 5. Bronstad PM, Bowers AR, Albu A, Goldstein R, Peli E. Driving with central field loss, I: effect of central scotomas on responses to hazards. JAMA Ophthalmol. 2013;131(3):303-30923329309PubMedGoogle ScholarCrossref 6. Bowers AR, Mandel AJ, Goldstein RB, Peli E. Driving with hemianopia, I: detection performance in a driving simulator. Invest Ophthalmol Vis Sci. 2009;50(11):5137-514719608541PubMedGoogle ScholarCrossref 7. Bowers AR, Mandel AJ, Goldstein RB, Peli E. Driving with hemianopia, II: lane position and steering in a driving simulator. Invest Ophthalmol Vis Sci. 2010;51(12):6605-661320671269PubMedGoogle ScholarCrossref 8. Bronstad PM, Bowers AR, Albu A, Goldstein RB, Peli E. Hazard detection by drivers with paracentral homonymous field loss: a small case series. J Clin Exp Ophthalmol. 2011;S5:001Google Scholar 9. Legge GE. Driving with central field loss. JAMA Ophthalmol. 2013;131(3):393-39523329348PubMedGoogle ScholarCrossref 10. Fletcher DC, Schuchard RA, Renninger LW. Patient awareness of binocular central scotoma in age-related macular degeneration. Optom Vis Sci. 2012;89(9):1395-139822863789PubMedGoogle ScholarCrossref 11. Desapriya E, Wijeratne H, Subzwari S, et al. Vision screening of older drivers for preventing road traffic injuries and fatalities. Cochrane Database Syst Rev. 2011;16(3):CD00625221412894PubMedGoogle Scholar http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png JAMA Ophthalmology American Medical Association

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Publisher
American Medical Association
Copyright
Copyright © 2013 American Medical Association. All Rights Reserved.
ISSN
2168-6165
eISSN
2168-6173
DOI
10.1001/jamaophthalmol.2013.4259
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Abstract

In reply Desapriya and colleagues commented on our use of simulation in evaluating detection performance of drivers with CFL. Although driving assessments using open-road courses have high face validity, such studies are limited by the inability to control whether, when, and where hazards appear.1-4 By comparison, a high-fidelity driving simulator, such as the one used in our study,5 provides a safe, controlled environment in which to conduct much-needed studies to evaluate the effects of different types and levels of vision impairment on driving performance.5-8 Using a driving simulator, we have been able to repeatedly evaluate detection of potential pedestrian hazards under exactly the same conditions for all participants in a manner that is impossible in an on-road study1 (even using a closed-road course). In the prior on-road study of drivers with “mild” central field loss (CFL)3 that Desapriya and colleagues noted, there were only 2 stunt actor appearances per driver compared with 104 pedestrian appearances per participant in our driving simulator study. Our main finding was that participants with CFL had significantly and dangerously longer reaction times to pedestrians who appeared in scotomatous areas than in nonscotomatous areas of their visual field. Our sample size was relatively small; however, the effects we found were large and highly significant owing to our use of a repeated-measures design with multiple presentations of hazards. In our study, participants were aware that we were evaluating their ability to detect pedestrians (and where these pedestrians tended to appear) and may therefore have responded more quickly than they would in real life.9 Thus, our results might even underestimate the risk that central scotomas pose. We agree with Desapriya and colleagues that other factors, besides vision impairment, affect reaction times in older drivers. However, it is unlikely that any such factors affected our results. Our main analysis was a within-subjects comparison of reaction times between scotomatous and nonscotomatous regions of the visual field. Other factors such as cognitive slowing, muscle weakness, or the effects of medications would have affected reaction times in scotomatous and nonscotomatous regions to a similar extent. Desapriya and colleagues wrote, “A surprising finding from this study is that most individuals from the CFL group meet the current restricted driver's licensing requirements in the United States.” That was not a finding of our study; we intentionally set the inclusion criteria to ensure that we recruited individuals with CFL who could legally drive somewhere in the United States, albeit with a restricted license. The fact that such patients are licensed to drive does not mean that they “are operating motor vehicles without realizing that their vision is impaired,” as Desapriya and colleagues wrote. Most such patients and their doctors are well aware of their visual acuity loss. However, patients with CFL are often unaware of their scotoma10 and should be advised about how it might impair their ability to respond to hazards when driving. Indeed, lack of data about the effects of central scotomas on driving performance was the main reason for conducting our study. We agree with Legge9 that, besides the mere presence, the location of the scotoma could be important and that a follow-up study including patients with scotomas above or below the preferred retinal locus is needed; we are completing such a study. Desapriya and colleagues concluded that there is an urgent need for driver's licensing agencies to establish reliable visual function screening tests. While we agree in principle with this statement, the data for such recommendations cannot, unfortunately, be derived from meta-analyses of any existing literature. This was highlighted in the recent Cochrane review by Desapriya et al11 of the effects of vision screening on the prevention of older driver–related crashes, in which they found no studies that even met the inclusion criteria. In fact, we are still a long way from understanding how different types of vision impairment affect specific driving skills and driving safety. Therefore, we need to focus our research efforts on building a strong evidence base for the effects of vision impairment on driving performance, as our recent studies begin to do. Back to top Article Information Correspondence: Dr Bronstad, Schepens Eye Research Institute, 20 Staniford St, Boston, MA 02114 (matthew_bronstad@meei.harvard.edu). Conflict of Interest Disclosures: None reported. References 1. Bowers AR, Tant M, Peli E. A pilot evaluation of on-road detection performance by drivers with hemianopia using oblique peripheral prisms. Stroke Res Treat. 2012;2012:17680623316415PubMedGoogle Scholar 2. Bowers AR, Peli E, Elgin J, McGwin G Jr, Owsley C. On-road driving with moderate visual field loss. Optom Vis Sci. 2005;82(8):657-66716127330PubMedGoogle ScholarCrossref 3. Lamble D, Summala H, Hyvärinen L. Driving performance of drivers with impaired central visual field acuity. Accid Anal Prev. 2002;34(5):711-71612214966PubMedGoogle ScholarCrossref 4. Haymes SA, LeBlanc RP, Nicolela MT, Chiasson LA, Chauhan BC. Glaucoma and on-road driving performance. Invest Ophthalmol Vis Sci. 2008;49(7):3035-304118326696PubMedGoogle ScholarCrossref 5. Bronstad PM, Bowers AR, Albu A, Goldstein R, Peli E. Driving with central field loss, I: effect of central scotomas on responses to hazards. JAMA Ophthalmol. 2013;131(3):303-30923329309PubMedGoogle ScholarCrossref 6. Bowers AR, Mandel AJ, Goldstein RB, Peli E. Driving with hemianopia, I: detection performance in a driving simulator. Invest Ophthalmol Vis Sci. 2009;50(11):5137-514719608541PubMedGoogle ScholarCrossref 7. Bowers AR, Mandel AJ, Goldstein RB, Peli E. Driving with hemianopia, II: lane position and steering in a driving simulator. Invest Ophthalmol Vis Sci. 2010;51(12):6605-661320671269PubMedGoogle ScholarCrossref 8. Bronstad PM, Bowers AR, Albu A, Goldstein RB, Peli E. Hazard detection by drivers with paracentral homonymous field loss: a small case series. J Clin Exp Ophthalmol. 2011;S5:001Google Scholar 9. Legge GE. Driving with central field loss. JAMA Ophthalmol. 2013;131(3):393-39523329348PubMedGoogle ScholarCrossref 10. Fletcher DC, Schuchard RA, Renninger LW. Patient awareness of binocular central scotoma in age-related macular degeneration. Optom Vis Sci. 2012;89(9):1395-139822863789PubMedGoogle ScholarCrossref 11. Desapriya E, Wijeratne H, Subzwari S, et al. Vision screening of older drivers for preventing road traffic injuries and fatalities. Cochrane Database Syst Rev. 2011;16(3):CD00625221412894PubMedGoogle Scholar

Journal

JAMA OphthalmologyAmerican Medical Association

Published: Jun 1, 2013

References