Evidence-base for low vision rehabilitation
Evidence-based practice means asking the question “what is the evidence for the effectiveness of a given intervention and how much of a difference might it make to the well being of your patient?” When all medical intervention has been tried to prevent or alleviate the effects of visually disabling disease, all that can then be offered is help to make the best possible use of residual vision. How is this best achieved?
This is of course a complex problem since rehabilitation covers many different aspects of activity; mobility is one (use of a cane or guide dog) and reading aids another. Other aspects include help in the home with daily tasks and social rehabilitation; ensuring particularly elderly visually impaired people do not become isolated. The need for psychological support must not be forgotten since losing sight is often compared with severe bereavement and much help can be provided to people who need help to come to terms with their loss and get on with their lives.
Some of these interventions are delivered in the context of social services, so research underlying the effectiveness of these methods falls within the domain of social rather than medical science. But this does not mean that good evidence is not needed. Low vision therapists often argue amongst themselves about what they believe to be the best way, citing examples of individual successes, but in the end these arguments are nothing more than expressions of opinion. Often views can be very strongly held which means that the necessary scientific objectivity to conduct unbiased investigations is lacking.
In terms of the medical model for low vision interventions, such as vision aids and mobility and orientation training, there is little good evidence to be found. On the Cochrane library, there is one review on mobility and orientation and another protocol on vision aids for reading. Another review from the USA is listed in the Database of Abstracts of Reviews of Effectiveness and a total of 19 randomised controlled trials of some relevance to low vision in the Central Controlled Trials register. The review on mobility and orientation found no studies meeting the inclusion criteria, and comments on the paucity of good evidence in the whole field.
One problem is that these studies need validated outcome measures, including quality of life as well as vision. While an increasing number now exist, there is a need for researchers in the field to agree on common standards which can be used by different groups to allow comparisons and summaries to be made of the findings.
There is growing awareness among participants in this area of research that the evidence base is poor and steps are now being taken to remedy the situation.