Li Li
Schepens Eye Research Institute,
Harvard Medical School
will speak on
Heading Perception of Tunnel-Vision Patients
Abstract:
Previous studies showed that normal-vision observers could
accurately perceive heading from a radial random-dot flow pattern even
when the central field of view was restricted to 50~100. While
tunnel-vision patients have lost almost all their peripheral vision, their
central visual field is restricted but functions normally. Here, we
investigate whether tunnel-vision patients can perceive heading from optic
flow. Two groups of retinitis pigmentosa (RP) patients (with ~50 and ~100
visual field respectively) and age-matched controls viewed displays
simulating observer translation (2m/s) over a random-dot or a
textured-mapped ground. Subjects adjusted a probe to indicate perceived
heading. In the Full-field Viewing condition, the subject viewed the full
display (1120H x 950V) with free fixation; in the Aperture Viewing
condition, the subject viewed the display through an aperture with a
fixation point at the center. The size of the aperture was either 50 or
100 depending on the size of the patient's visual field. In the
Full-field condition, two RP patients (one from each group) could
accurately perceive heading and so could all age-matched controls. The
other two RP patients (with ~100 visual field) displayed center bias. In
the Aperture condition, RP patients displayed a much stronger center-bias
than the age-matched controls. We conclude that with full display and
free fixation, scanning eye movements allowed some RP patients to judge
heading accurately. With restricted display and controlled fixation,
patients had very poor heading performance. Results suggest that scanning
eye movements are important for accurate heading perception with a small
visual field.
The lecture will take place in the
Lecture Hall, Room 203, 44 Cummington St.
on Wednesday, April 5, 2000
at 1:00 pm
Hosted by the
Brain and Vision Research Laboratory