Amy Doherty

Object Detection in the Ring Scotoma of a Monocular Bioptic Telescope

OBJECTIVE To evaluate the ability of the fellow eye to detect stimuli in the area corresponding to the ring scotoma (blind area) of a monocular bioptic telescope in simple conditions (conventional perimetry) and in more visually demanding conditions. METHODS A computerized dichoptic perimeter enabled separate stimuli to be presented to each eye of 7 bioptic users and 7 nonusers. The bioptic ring scotoma was mapped by presenting the stimulus to the telescope eye only. Detection tests were then conducted under binocular viewing, with stimuli presented only to the fellow eye in a 2 × 2 × 2 design with or without telescope, on plain gray or patterned (spatial noise) background, and with passive (looking at cross) or active (reading letters) fixation task. RESULTS No significant differences were noted in fellow-eye detection with (86%) and without (87%) a bioptic. The detection rate was significantly reduced on the patterned background and in the active fixation task. CONCLUSIONS To our knowledge, this is the first study to demonstrate fellow-eye detection in the area of the ring scotoma with a monocular bioptic telescope under more realistic and visually demanding conditions than conventional perimetry. These results should ease the concern that the monocular ring scotoma might cause blindness to traffic outside the field of the telescope.

The effect of strabismus on object detection in the ring scotoma of a monocular bioptic telescope.

People with reduced visual acuity are permitted to drive with the aid of bioptic telescopes in the USA, the Netherlands, and Canada. When viewing through a monocular bioptic telescope, suppression of the deviating eye in strabismus may reduce the ability of the non‐telescope eye to detect objects whose images fall in the ring scotoma area of the telescope eye, which could impair detection of traffic‐relevant events. This ability to detect stimuli in the ring scotoma area was compared for strabismic and non‐strabismic patients.

Hazard detection with monocular bioptic telescopes in a driving simulator

ABSTRACT Purpose: Recently we developed a driving simulator paradigm to evaluate detection of road hazards when using a bioptic telescope and conducted an initial study using normally-sighted observers with simulated vision loss. We now extend our investigation to quantifying the extent to which visually impaired bioptic users are able to use their fellow (non-telescope) eye to compensate for the ring scotoma of a monocular bioptic telescope. We tested the hypothesis that detection rates would be higher in binocular viewing (fellow eye could potentially compensate) than monocular viewing (fellow eye patched so it could not compensate) for pedestrian hazards present in the scene only while the telescope was being used. Methods: Sixteen bioptic telescope users (17-80 y) completed six test drives, including three with binocular viewing interleaved between three with monocular viewing. While driving, they used their own monocular bioptic telescopes to read information on highway road signs (n = 71) and pressed the horn when they saw a pedestrian hazard (n = 50). Twenty-six of the pedestrians were programed to appear, run on the road ahead of the driver for 1s within the ring scotoma and then disappear, within the period when participants were reading signs through the bioptic. The timing of the head movement to look into and out of the bioptic was determined and events were then categorized by whether or not the pedestrian hazard was present in the scene only while using the bioptic. Results: When pedestrian hazards were in the scene only while subjects were using the bioptic to read a sign, detection rates were significantly higher in binocular than monocular viewing (68% vs. 40%). However, when pedestrians when subjects had a brief view of the pedestrian either beforeor after looking through the bioptic, then detection rates did not differ in binocular and monocular viewing (78% vs. 79%). By comparison, when not using the bioptic detection rates were higher (> 90%) and reaction times were shorter (without 0.95 s vs. with 1.25 s) Conclusions: Our results suggest that under binocular viewing conditions the fellow eye was able to compensate for the ring scotoma to a certain extent when subjects used a monocular telescope to read road signs; however, performance was not as good as without the bioptic.

Hazard detection with a monocular bioptic telescope

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.