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Vision Impairment in Stroke: Intervention Or Not Coordinated by the Clinical Trials Research Centre, University of Liverpool
VISION Trial emblem VISION Trial Vision in Stroke

Trial summary

Last reviewed 13 May 2011 by Rachel McMahon

VISION has been undertaken to explore the visual rehabilitation of patients who lose either the left or the right half of the visual field in both eyes, a condition known as homonymous hemianopia, following a stroke.

Why visual field loss matters

A stroke can affect individuals in many different ways and leave a variety of persisting side effects. Visual field loss is a commonly reported side effect of stroke and can seriously impact on 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.

Despite this, service provision for stroke patients with suspected visual field loss is inconsistent, with a large number of stroke services providing no formal visual assessment. Furthermore, there are no clear guidelines on how stroke patients with visual field loss should be visually rehabilitated.

What homonymous hemianopia looks like

Below are examples of what a person with left or right homonymous hemianopia might see, compared with normal vision. In each example the shaded half is the part of the scene that is lost.

Normal vision
Normal vision: the whole scene is visible to both eyes.
Lost Left homonymous hemianopia
Left homonymous hemianopia: the left half of the scene is lost in both eyes.
Lost Right homonymous hemianopia
Right homonymous hemianopia: the right half of the scene is lost in both eyes.

The three treatment arms

VISION compares the clinical effectiveness of three different treatment methods to which patients are randomly assigned.

  1. Prism glassesAn optical plastic membrane displaces the images viewed through the prism.
  2. Visual search trainingTraining encourages a person to look systematically to the right and to the left.
  3. Information only, the control groupParticipants receive information about visual field loss and standard care, with no additional therapy.

How the trial runs

By using visual field assessments at 6, 12 and 26 weeks after treatment start, in combination with a quality of life questionnaire completed by patients, the trial hopes to demonstrate whether rehabilitation methods are better at improving functional outcome in the study population compared with information only.

Additionally, it is hoped that it will be possible to say whether prism glasses or visual search training are the most effective at improving functional outcome.

Patients with homonymous hemianopia after stroke Random assignment to one of three groups Treatment period as allocated Prism glasses Visual search training Information only Visual field assessment and quality of life questionnaire at 6, 12 and 26 weeks
Trial flow: patients are randomly assigned to one of three treatment groups, then assessed at 6, 12 and 26 weeks.

Related information

Unfamiliar with the terms used here? The glossary explains homonymous hemianopia, prism, visual field and visual scanning in plain language.