This study will be carried out in Ontario, Canada (University of Waterloo) and Hong Kong
(The Hong Kong Polytechnic University). There are two conditions: Active brain
stimulation + perceptual training and sham/placebo brain stimulation + perceptual
training. This study uses a between-subjects design, such that half of all participants
will be placed in the active stimulation group and half will be placed in the sham group.
Participants will be recruited from university-affiliated clinics and local clinical
practices. Following full informed consent, participants will complete baseline testing
and clinical testing to confirm that they meet eligibility criteria including: a
diagnosis of macular degeneration without any additional eye disease, impaired vision but
with enough visual acuity that the computer monitor can still present readable word, and
no contraindications for brain stimulation interventions. Eligible participants will then
be randomized to either receiving the active stimulation during perceptual training or
the placebo stimulation during perceptual training.
The primary outcome measure is verbal reading accuracy for sentences presented on a
computer screen following a Rapid Serial Visual Presentation (RSVP) task in which a
single word is presented on the screen at a time. Participants will freely observe the
words and will indicate the words on the screen verbally. The secondary outcome measures
are contrast sensitivity and crowded and uncrowded visual acuity as measured by Freiburg
Visual Acuity & Contrast Test (FrACT) using the Landolt C stimulus. The "C"'s gap will be
oriented randomly, and the participant will indicate the orientation of the stimulus.
Crowded visual acuity will be assessed with Landolt C surrounded by a solid ring, while
uncrowded visual acuity will be assessed with the Landolt C alone. The Test of contrast
sensitivity will measure the amount of contrast required relative to the background to
identify the orientation of the "C". The Hong Kong Polytechnic University has an
additional set of secondary outcome measures of temporal and spatial visual span.
Temporal visual span will be assessed using Chinese trigrams presented horizontally or
vertically at the centre for a range of presentation times. Spatial visual span will be
assessed using Chinese trigrams presented horizontally or vertically at different
character positions for a fixed presentation time. Participants will be asked to
recognize all three characters in a correct order.
The study consists of 9 sessions plus 1 additional session particularly for Hong Kong
Polytechnic University
Session 0: This session only applies for The Hong Kong Polytechnic university, that
horizontal and vertical temporal and spatial visual span will be collected.
Session 1: The first session will include the clinical evaluation. In addition, the pre
tests of all outcome measures will be collected (RSVP performance, crowded and uncrowded
visual acuity, contrast sensitivity).
Sessions 2-7: Brain stimulation sessions. Participants will undergo roughly 1 hour of
perceptual training, performing the RSVP task. The first 25 minutes of this training will
include either sham or active brain stimulation. A given participant will receive the
same kind of stimulation for all 6 training sessions.
Session 8: No brain stimulation will occur. Post test outcome measures will be collected
(RSVP performance, crowded and uncrowded visual acuity, contrast sensitivity, horizontal
and vertical temporal and spatial visual span).
Session 9: 30 day follow up. 30 days after the final training session, participants will
again perform the outcome measures without brain stimulation to determine the long term
benefit of the perceptual training + brain stimulation.