Hazard detection with a monocular bioptic telescope

Abstract

Purpose The safety of bioptic telescopes for driving remains controversial. The ring scotoma, an area to the telescope eye due to the telescope magnification, has been the main cause of concern. This study evaluates whether bioptic users can use the fellow eye to detect in hazards driving videos that fall in the ring scotoma area. Methods Twelve visually impaired bioptic users watched a series of driving hazard perception training videos and responded as soon as they detected a hazard while reading aloud letters presented on the screen. The letters were placed such that when reading them through the telescope the hazard fell in the ring scotoma area. Four conditions were tested: no bioptic and no reading, reading without bioptic, reading with a bioptic that did not occlude the fellow eye (non-occluding bioptic), and reading with a bioptic that partially-occluded the fellow eye. Eight normally sighted subjects performed the same task with the partially occluding bioptic detecting lateral hazards (blocked by the device scotoma) and vertical hazards (outside the scotoma) to further determine the cause-and-effect relationship between hazard detection and the fellow eye. Results There were significant differences in performance between conditions: 83% of hazards were detected with no reading task, dropping to 67% in the reading task with no bioptic, to 50% while reading with the non-occluding bioptic, and 34% while reading with the partially occluding bioptic. For normally sighted, detection of vertical hazards (53%) was significantly higher than lateral hazards (38%) with the partially occluding bioptic. Conclusions Detection of driving hazards is impaired by the addition of a secondary reading like task. Detection is further impaired when reading through a monocular telescope. The effect of the partially-occluding bioptic supports the role of the non-occluded fellow eye in compensating for the ring scotoma.

Roles of motion perception and visual acuity for driving hazard perception

“…While, this study did not show an impact on HP performance due to the change in visual acuity, this finding does not necessarily suggest low visual acuity doesn’t have any negative impacts in the real world driving. At first look, the findings of this study might seem in contradiction of the findings of our previous study, which showed visually impaired people had lower HP scores than normally sighted 24 . In addition to the difference between the participants groups involved in the two studies, the frame rate of visual stimuli was also a factor causing the difference.…”

“…The driving images in this study were effectively presented at 2.5Hz, as only one out of 10 frames was shown to participants. To investigate the effect of such a low frame rate of video stimuli, results of this study were also compared to the findings of our previous HP study which used full 25Hz videos 24 . Results of no-mask-with-diffuser in this study were compared to that of visually impaired participants in previous study, and the results of no-mask-no-diffuser condition of this study were compared to that of normally sighted participants in previous study.…”

“…These drivers’ low level of visual acuity sets them apart from the drivers with conventional levels of visual acuity. Bioptic drivers use the telescope mainly for navigation and reading the signs 22,23 , which means that they use their bioptic telescope for only a small proportion of total driving time, adhering to the bioptic driving guidelines which addresses concern that use of the bioptic telescope may block the field of view 24 . Luo and Peli 12 recorded the actual driving of two bioptic drivers and found that their bioptic use was as low as 1%, meaning that for 99% of the time these drivers drove with their low visual acuity.…”

Bioptic Telescope Use in Naturalistic Driving by People with Visual Impairment

“…Our previous studies of bioptic telescopes in the controlled conditions of the laboratory, including simulated driving scenarios, have shown that the restricted visual field can affect detection of peripheral stimuli and hazards to some extent when looking through the telescope. [11][12][13][14][15] Thus, bioptic driving guidelines suggest that bioptic drivers should dip their head only briefly when needed to look through the telescope(s) to gain a magnified view of distant objects. 16 However, how and when the bioptic is actually used in habitual driving is still not well understood.…”

Hazard detection with monocular bioptic telescopes in a driving simulator

“…In our previous studies, when using static stimuli over a stationary patterned background, the fellow eye compensated fully for the ring scotoma, 18,22 while for real world driving videos, only about 50% of hazards were detected by the fellow eye. 23 Recently we developed a more realistic driving simulator paradigm to investigate hazard detection when using a bioptic telescope. 27 The paradigm addressed some of the limitations of the earlier studies (such as prolonged viewing through the bioptic and lack of engagement in a driving task).…”