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Rehabilitation of visual disorders after brain injury

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    Rehabilitation of visual disorders after brain injury. By j zihl(Pp 187, £29.95, Published by Psychology Press, Hove, 2000. ISBN 0 86377 898 4.

    This is the second series on neuropsychological rehabilitation fostered by Barbara Wilson and Ian Robertson (the first beingNeural repair, transplantation, and rehabilitation by R Barker and S Dunnett). The renewed interest is welcome. Josef Zihl is one of the first clinical scientists, together with collaborators such as von Cramon, to have put a concentrated effort into rehabilitation of visual disorders, spanning a period of 2 decades. Much of this pioneering work lies in Germany, stemming from an older tradition going back to Poppelreuter, and the current book should make the developments better known outside that country. It remains something of a curiosity that visual rehabilitation is scarcely pursued in Britain and the United States, especially given the seminal animal work (by Cowey in Britain and Mohler and Wurtz in the United States) clearly demonstrating the potential capacity for recovery after V1 lesions in the monkey, with practice regimes. Indeed, Zihl's own work acknowledges the influence of these animal studies on his own research.

    The Series preface describes this work as a “modular handbook.” Handbook it is not. Rather it is a compact and relatively short account that is more like a progress report, full of interesting approaches described in mid-stream of the research, much of it still to be completed. It is broad ranging, the largest and most advanced section (about half of the book) being on visual field disorders, but progressing to visual acuity, colour vision, visual space perception (including Balint's syndrome), visual agnosia, and a final brief section on the special problems of a central scotoma. Each section starts usefully with evidence of spontaneous recovery, which is the baseline from which rehabilitative efforts must be assessed. Such efforts are almost entirely based on intensive practice (what I have called “grindsight”). Zihl is very cautious, lacing the evidence with statements such as “our observations produce preliminary evidence that spatial contrast sensitivity can, in principle, be improved by specific and systematic practice. However, the limited number of cases does not allow definite conclusions to be drawn ........” (p 96). He is also careful to distinguish between measurable effects in the laboratory and their “ecological value” to the subject in terms of any benefit in everyday life. In some regards he is over-cautious—for example, in his speculation (with von Cramon) “that recovery of visual field defects can only be expected with complete striate cortex injury” (p 34). Of course, complete V1 lesions are almost always accompanied by additional damage, when animal work demonstrates a reduced residual capacity. But a complete but restricted V1 removal in the monkey still allows further recovery to take place.

    Anyone wishing to find practical approaches for helping patients across a range of visual disorders will find this a useful, humane, and dedicated book. He or she will have to work through a compact monograph and share Zihl's experience with him, rather than find a collection of shorthand recipes. It will be rewarding work.