Friday 22 January 2016
Funded by the Stroke Association, the VISION trial was undertaken to explore the visual rehabilitation of patients who lose half of their visual field in both eyes following stroke. This condition is known as 'homonymous hemianopia'.
Published in the journal, Neuro-Ophthalmology, a new study shares insights learned from recruitment of participants to the VISION trial, and how this may inform future, similar trials.
What is visual field loss?
The 'visual field' is the amount of a person's surroundings they can see at any one time.
Visual field loss is a reduction of the visual field. It is a commonly reported side effect of stroke and can seriously impact on a person's functional ability and quality of life.
Individuals who experience visual field loss following stroke can be more prone to falls and their participation in rehabilitation may be hampered.
What is the VISION trial?
The VISION (Visual Impairment in Stroke; Intervention Or Not) trial is exploring the visual rehabilitation of patients who lose either the left or right half of the visual field in both eyes (homonymous hemianopia) following stroke.
The trial is comparing the clinical effectiveness of three different treatment methods to which patients were randomly assigned:
1. Prism glasses - the prisms direct images from the damaged portion of the person’s visual field into the still functioning part of their visual field.
2. Visual Search Training - re-training a patient's eye movements to make them more efficient in searching the still functioning part of their visual field.
3. Information Only - used as a 'control group' to compare with the other treatments.
All patients were given visual field assessments at six weeks, three months and six months after the start of their treatment, used in combination with a patient completed quality of life questionnaire.
From this, the trial hopes to demonstrate whether rehabilitation methods were better at improving the functional outcomes of the patients who took part, when compared to giving the patients information only.
Additionally, it is hoped that it will also be possible to say whether prism glasses or visual search training were most effective at improving the functional outcome of patients.
What does the latest research show?
The new study found that of 1,171 patients with suspected homonymous hemianopia who were screened for the trial, only 178 patients were eligible to take part. The main reason people could not take part was because they had made a full or partial recovery from their visual field loss. In fact, full or partial recovery of visual field loss on one side accounted for almost half of those patients who were ineligible. This is a positive finding for stroke outcomes, as even partial recovery of visual field loss on the affected side may have much less impact on a person's functional ability, than a complete loss of vision on that side.
For future trials in this research area, the study suggests that recruitment of patients may be increased by improved training of trial staff in the research processes involved (enhancing their ability to screen and recruit patients), as well as using outcomes from treatment that can be measured at home, rather than in the hospital.
How can I find out more?
The final results from the VISION trial are yet to be published. However, you can find out more about the trial by visiting the VISION trial website here.
Dr Fiona Rowe is Reader in Health Services Research at the University of Liverpool, and Chief Investigator on the VISION trial. Find out more about her wider research into vision problems after stroke by visiting her webpage.