Introduction

From the very beginning of neuroscience, vision research has mainly been concerned with the elucidation of the nature of various visual deficits and the identification of the location of brain injury responsible for these deficits (Zeki, 1993). Early clinical reports on patients showing selective loss of visual functions and abilities following acquired posterior brain injury have suggested a functional segregation of the visual cortex, a concept that many years later has been verified on the basis of combined anatomical, electrophysiological and behavioural evidence (Desimone & Ungerleider, 1989; Grill-Spector & Malach, 2004; Zeki, 1993). Enormous progress has been made in understanding the neurobiological basis of visual perception and the neuropsychology of vision is still a major topic in neuroscience. However, this progress is not reflected in the study of recovery of visual function in patients with acquired brain injury. The related findings are not included in neuropsychological rehabilitation, possibly because visual-perceptual disorders are not considered as cognitive deficits (see, for example, Cicerone et al., 2005; Halligan & Wade, 2005; Ponsford, 2004). At first sight, this is difficult to understand given the fact that about 30% of patients with acquired brain injury suffer from visual disorders (Clarke, 2005; Hier, Mondlock & Caplan, 1983a; Rowe et al., 2009; Sarno & Sarno, 1979; Suchoff et al., 2008). Furthermore, visual disorders often either directly affect cognitive performance or exacerbate cognitive deficits (Uzzell, Dolinskas, & Langfitt, 1988), which may interfere with the rehabilitation of other cognitive impairments and impede vocational rehabilitation efforts (Groswasser, Cohen & Blankstein, 1990; Patel, Duncan, Lai, & Studenski, 2000; Reding & Potes, 1988; Rowe et al., 2009). However, it does not seem that a lack of interest in the recovery of vision or visual rehabilitation can account for the fact that the advances in understanding the neurobiological basis of visual perception have not led to greater progress in neuropsychological rehabilitation. As early as 1867, Zagorski reported the case of a 35-year-old lady who complained of loss of vision on the left side. Perimetric testing revealed a complete left-sided

hemianopia, probably caused by a right-sided occipital haemorrhage. Eight days later the patient noticed return of light vision in her left hemifield; 6 weeks later she reported having full vision again. Weekly visual field measurements were in agreement with the patient’s reports: the region of blindness shrank successively and vision eventually returned to the left hemifield (see Figure 1.1). Zagorski’s single case report is probably the first report on recovery of vision after acquired brain injury. In their “Handbook for Neurologists and Ophthalmologists” [author’s translation] Wilbrand and Saenger (1917) dedicated a comprehensive chapter to the natural course of complete cerebral blindness. According to their observations, vision recovered first in one hemifield; a few cases later showed complete return of vision in both hemifields. In most cases recovery of vision took place within hours or days; in some patients, however, the process of recovery was much slower and was not completed for several weeks. A similar course was observed in subjects with homonymous hemianopia. In the same year (1917/1990), Poppelreuter published his monograph on visual disturbances after occipital gunshot wounds, in which he reported not only the results of his detailed diagnostic visual disorders assessment, but also his observations on spontaneous recovery and the effect of systematic treatment. Poppelreuter preferred an experimental approach for assessing and treating his patients. In his view, conventional assessment and treatment methods were too “crude” (i.e., inaccurate), and systematic rehabilitation measures did not exist. His approach was also very pragmatic, i.e., ecologically valid, which is exemplified by his statement that “any intervention should, at the very least, have as its aim that the man should again be able to converse comprehensibly, to write his own letters, to read a newspaper, and to calculate his expenses by himself” (p. 5). Poppelreuter pointed out that functional impairment in vision in the acute stage may often be exaggerated since unspecific cognitive and affective alterations can affect the use of spared visual capacities. Since complete spontaneous recovery was the exception rather than the rule in his patients, rehabilitation measures were required to reduce their visual handicap and improve their independency in daily life activities and, thus, their “usefulness for society”. Poppelreuter was aware of the difficulty of attributing an improvement unequivocally to the treatment: “Only exact control of the effect [of treatment] offers a substantial argument for the systematic training effect over a short period of time, namely using a work task which remains constant” (p. 240). He developed training methods that specifically aimed at improving the reading impairments in patients with visual field loss (i.e., hemianopic dyslexia), which have already been described by Mauthner in 1881 and Wilbrand in 1907 (see Schuett, Heywood, Kentridge & Zihl, 2008a, for a comprehensive review). Poppelreuter correctly noticed that parafoveal field loss is not only associated with impaired global text processing but also with an impairment of the “co-ordination of the reading gazeshifts”, which becomes manifest as a distortion of the typical, staircase-like oculomotor reading pattern. He therefore taught patients to compensate for

Figure 1.1 Spontaneous recovery of vision in Zagorski’s case with left homonymous hemianopia (1867). Left panel: Visual field of the left eye; right panel: visual field of the right eye. (A) Outcome of perimetric testing on 11 June 1867; (B) on 26 June 1867; (C) on 5 July 1867. On 27 July, Zagorski found complete recovery of vision in the left hemifield.