For low vision specialists and those who consult them
Eccentric viewing training: how do we know it works?
August 4, 2009Posted by on
I am involved in the design of a randomised controlled trial to assess how useful eccentric viewing training is for people with central field loss. It’s proving to be a much harder question to answer than you may think.
Eccentric viewing is the technique by which people with central vision loss use a specific area of peripheral retina in place of the fovea in order to see. Whilst we have shown that this technique develops naturally in many cases (PDF), it is widely thought that training patients to make this adaptation can increase its use: for example, after training people may be able to use this technique for reading, not just for looking at a fixation target.
Eccentric viewing training is offered by many low vision clinics: notably by Optima in west England; the Veterans Administration in the USA; some centres in Australia; and many places in Scandinavia. One reason that it isn’t more widely used in the UK is that the Health Service require robust evidence (usually in the form of a randomised controlled trial) before agreeing to fund any intervention. This is what we are trying to perform, so that its efficacy can be assessed properly.
The problem is that eccentric viewing training is that it can not be performed in isolation: it can only really be used as part of a complete rehabilitation strategy including prescribing magnification, advice on steady eye strategy, advice on lighting and so on. This makes teasing out the relative effect of EV training versus all of the other elements of low vision rehab hard. We think we have managed to work out an appropriate study design, but it hasn’t been straightforward.
Obviously as a researcher I have to be impartial and I don’t want to speculate on what our results will be. However as a clinician I have seen how important good eccentric viewing is for people with central vision loss and would be surprised if we did not find that EV training is useful. Some of my co-investigators are more sceptical….so watch this space!
Results will be published some time in the next 4 years.