Abstract
Purpose: :
To compare the on-road driving performance of visually impaired drivers using bioptic telescopes with age-matched control drivers who had visual acuity that met the regular state vision standard for driving and to identify the types of driving difficulties that characterize bioptic drivers.
Methods: :
Participants included 23 persons (Mean age = 33 ± 12 yrs) with visual acuity of 20/60 or worse who were legally licensed to drive through the State of Alabama’s bioptic driving program, and 23 visually normal age-matched controls (Mean age = 33 ± 12 yrs) with visual acuity that met the driver licensing requirement in Alabama. The bioptic drivers had a range of non-progressive ocular conditions (e.g., ocular albinism, optic atrophy, Stargardt’s disease). On-road driving performance was assessed in a dual-brake vehicle on a 14.6-mile course in Birmingham, AL that included both city and suburban driving including controlled access highways. Overall driving performance was rated on a 5-point scale by two "backseat" raters, who also independently rated 24 specific driving maneuvers with respect to eight driving behaviors (e.g., scanning, lane position, steering steadiness, speed, obey signals).
Results: :
Binocular visual acuity of the bioptic drivers ranged from 20/60 - 20/200. 96% (22/23) of the bioptic drivers, and 100% of the drivers with normal visual acuity received overall driving ratings that indicated the potential for safe driving. While the bioptic drivers demonstrated poorer performance than did the controls for lane positioning, steering steadiness and reporting signs, for the majority of the driving performance measures there were no significant group differences. Bioptic drivers also made more right head movements and tended to drive over the right (edge) lane marking of the road more often than did the controls.
Conclusions: :
This study demonstrates that many drivers with moderate central vision loss have the potential for safe driving using a bioptic telescope when compared against drivers of the same age who have normal central vision. These results will help to inform the assessment and training of bioptic drivers in order to optimize their driving performance and safety, allowing them to maintain independence, employment options and mobility within the community.