At the recent meeting of the International Neuro-ophthalmology Society in Geneva one of the most interesting presentations was given by two collaborators who disagreed on the interpretation of their joint findings. The atmosphere was more than usually stimulating. The disputed results are published in this issue of BJO (p 30).

It was Josef Zihl from Munich who in 1979, with von Cramon, put forward evidence that it might be possible with practice to extend areas of residual vision in cases with homonymous visual field defects secondary to occipital damage. I have always been sceptical of these findings.

In recent years the work …