recovery of visual field defects after stroke - a pilot implementation

Stroke is the most common cause of visual field defects.: roughly 25% of
chronic stroke patients have visual field defects (VFDs). VFDs, such as
hemianopia, interfere considerably with Activities of Daily Life (ADL) like
reading, exploration and navigation. Many studies have explored the human
potential for visual field recovery by visual training. Broadly, two strategies
have been studied. One strategy is to exploit subjects* voluntary control of
eye movements to raise the frequency of exploratory saccades towards their
defective field. This method, known as compensatory saccade training (CST) was
successful in about 35-75% of hemianopia patients suffering from a stroke. The
second approach aims to reduce the extent of the blind field and thus aims at
restoration of the visual field defect. For this purpose, Vision Restoration
Therapy (VRT) was developed. In our study, we used a custom training procedure
like VRT that we called *restorative function training* (RFT). RFT is a custom
made program different from VRT. However, RFT follows a very similar training
procedure as VRT: it stimulates the defective area.

Field enlargement following RFT has been shown in chronic stroke patients using
subjective perimetry. Visual field enlargement by itself does not necessarily
imply that behavioral performance improves. This raises the question whether
RFT actually leads to ADL improvement.
In earlier experiments, we observed VFE in most patients. Transfer effects of
VFE to other, untrained visual functions was observed for color- and shape
perception; transfer to activities of daily life were observed for reading
speed and car driving in a simulator, however only in trained patients with
VFE.

The goal of the study is twofold: (1) to study whether the earlier observed
positive *lab-results* (training effects) are also observed in a rehabilitation
setting, using evaluation techniques that are common in such a setting. If we
observe comparable positive training effects, the training method will be
implemented in the two participating rehabilitation institutes. (2) to gain
insight into the neural correlates of training-induced visual field enlargement
using imaging studies (fMRI, D.T.I. and Perfusion MRI). We expect that these
correlates will provide information about a) the optimal training
stimulus/stimuli; b) an optimal training method and c) the possibility to use
these correlates to develop a predictor for VFE.

Non-blinded repeated measures design.

The length of the study for a patient is 14 - 15 weeks, depending on the spread
of the pre- and post measurement days (the time between actual
application/intake procedure and start of the study not included).
Training: 13 weeks, 5 days per week, 1 hour (or 2x 30 mins or 4x 15 mins) per
day
Pre-measurements take place on 3 separate days: 2 days for the MRI experiments
en 1 day for perimetry, reading test en Goal Attainment Scaling (GAS, method to
evaluate functional recovery). Patients receive 3 questionnaires in advance
that they fill out and bring along on the 1st measurement day.
Post-measurements follow the same procedure. Patients receive training
instructions on pre-measurement day 1. The MRI experiments always take place in
Nijmegen. Perimetry, readingtest and GAS method will be administered to 8
patients in Utrecht and to 7 patients in Nijmegen. This is -as much as
possible- depending on place of residence.

visual Restorative Function Training. This training requires the patient to
look at a computer screen and respond with keyboard strokes. The patient is
required to fixate the gaze at a point no the screen and make a *covert
attention shift*, which means that the patient *mentally scans* the screen for
the presence of a stimulus.
Patients do not start with other visual training variants as long they are
included in the study. There are no medication restrictions.

In earlier studies we observed that practically all patients (voluntary
applicants) were able to conform to the requested training efforts. The same
applied to the perimetry measurements and the use of a head-mounted eye tracker.
The MRI scanner produces a lot of noise, therefore each patient receives
earplugs during scanning. As far as is known, there are no risks involved in
functional MRI acquisition. Patients are screened for MRI counter indications.
If these are absent, MRI scanning is safe.