Brain developmental disorders and those occurring in early childhood give rise to a variety of functional impairments. This does not however necessarily mean that these impairments, and their consequences for everyday life activities, are immutable, that the developmental processes and functional capacities of the (very) young brain are persistently affected or that the capacity of adaptation to these functional consequences in terms of learning will be irreversibly reduced or lost. Thus, specific and systematic intervention measures are needed as early as possible after brain injury, or the onset of brain dysfunction.

The principal aim of all early intervention measures is to minimise the degree of disability to facilitate self-reliance and independent daily life activities, with better participation in social and school activities and programmes, leading eventually to a higher quality of life. In essence, the child with visual impairment learns from life, for life.

All our knowledge, creativity and willingness are needed to develop tailor-made and problem-oriented solutions for intervention. Assessment of children with CVI to characterise the nature of each child’s condition for the purpose of planned intervention needs close cooperation by all disciplines involved. Intervention measures first of all aim to ameliorate the degree of visual disability in everyday life and reduce and minimise social disadvantage. This can be achieved by first eliciting and quantifying the limits of each visual capacity and working within these thresholds, when catering for each of the child’s needs. Approaches aimed at improving the affected visual capacity, for example, visual acuity, as well as efficient compensation strategies to overcome each visual dysfunction, e.g. visual field defects by gaze shifts; the use of technical aids, e.g. magnifying glasses; modified parenting strategies; and environmental modification in the home, are all considered. Often a combination of functional improvement and compensation techniques is the optimal strategy. Substitution for impaired or lost visual capacity is, at least in adults, the most frequently employed measure, because recovery of visual function after acquired brain injury appears the exception rather than the rule (Zihl 2011). For children with CVI, research results concerning substitution for impaired visual capacities are still somewhat sparse compared with adults. It appears that (spontaneous) recovery and adaptation to visual dysfunction in children occurs more often, provided that other functional systems particularly involved in vision are sufficiently spared and can develop normally. Attention, learning, memory and executive function, as well as motivation to learn more about the visual world are crucial prerequisites for flexible adaptation and the use of (spared) visual capacities in an optimal way. However, as Hoyt (2003) has shown, just living in a natural environment is not sufficient to elicit improvements in vision.

In principle, the following approaches aimed at minimising cerebral visual disability are possible:

Parents and caregivers need to be closely involved in all habilitational efforts, so that they can be shown how to help their child, and encouraged to integrate and appropriately extend any successful outcomes of intervention into their child’s activities of everyday living.

In adults with acquired CVI, spontaneous recovery has been reported for nearly all visual capacities; however, the degree of recovery is rarely complete (Zihl 2011). Children with severe CVI may develop some useful vision (Duchowny et al. 1974; Kaye and Herskowitz 1986; Lambert et al. 1987). The temporal course of recovery from cerebral blindness follows a typical pattern. In the first phase, children are able to detect moving and flickering light stimuli. Perception of (very) bright colours, contours and simple forms follows. Some children eventually develop contrast vision and visual acuity, which allow perception and identification of forms, objects, faces, scenes, etc. However, improvement can come to an end at each stage and for each visual capacity. Remarkable visual capacities (detection and discrimination of visual stimuli, movement vision) and visually guided behaviour (fixation, tracking, reaching) have been reported in single cases with congenital absence of normal occipital cortex or early bilateral occipital injury (e.g. Dubowitz et al. 1986; Summers and MacDonald 1990; Giaschi et al. 2003) indicating that development of vision may in part also be mediated by subcortical and/or extrastriate visual structures. Bova et al. (2008) reported the case of a boy with bilateral occipital lobe infarction at the age of 2.5 years. Complete cerebral blindness lasted a few weeks, then perception of movement returned, followed by progressive recovery of visual acuity, visual field and oculomotor functions. At the age of 6 years and 8 months, the boy had developed normal acuity (10/10), but still showed incomplete bilateral upper hemianopia (the pathway of the optic radiations serving the upper visual fields runs through the temporal lobe) and difficulties with complex visual form perception (e.g. overlapping figures) and complex visual-spatial tasks (e.g. Block design, Rey’s figure). Similar patterns of recovery have been reported by Innocenti et al. (1999), Werth (2007) and Muckli et al. (2009). These reports also illustrate that spontaneous recovery from cerebral blindness may take place over a number of years. Furthermore, the degree of recovery after brain injury early in life may not always be greater than later in adulthood, i.e. plasticity in childhood may also be limited, indicating that ‘young is not always better’ because vulnerability in the developing brain may be more crucial with respect to signal transmission and neuronal connectivity (Anderson 2003; Giza and Prins 2006). On the other hand, as Cioni et al. (2011) have pointed out, some mechanisms underlying brain plasticity may no longer be available at a later stage of maturation, in particular in the visual, sensorimotor and language systems.

As with adults, children with complete cerebral blindness are not always aware of their blindness (Barnet et al. 1970). In the course of recovery from cerebral blindness, visual perceptions without external stimuli (visual hallucinations) may occur (White and Jan 1992), which can be incorrectly taken to be real, and thus may impede awareness of blindness, or correct interpretation of any vision present, or improvement of vision. Many children with complete cerebral blindness also manifest cognitive dysfunction, which may impair awareness, as well as impeding visual assessment and intervention (Barnet et al. 1970; Jan et al. 1977; see also Matsuba and Jan 2006). Interestingly, Guzzetta et al. (2010) have found stronger awareness for visual stimuli in terms of ‘conscious feelings’ in subjects with cerebral blindness after early brain injury compared with subjects who have suffered brain injury later in life. Unfortunately, the use of electrophysiological correlates of vision may yield equivocal results because children with cerebral blindness may sometimes show preserved pattern-generated VEP (Frank and Torres 1979), but for many children with CVI, there is a good correlation between VEP and preferential looking methodologies (Mackie et al. 1995) showing that results warrant interpretation in the context of the whole clinical picture.

Partial recovery of vision has been reported in children with homonymous hemianopia, impaired visual acuity and contrast sensitivity (Groenendaal and van Hof-van Duin 1990; Porro et al. 1998), with a time of recovery that may take several years. Kedar et al. (2006) have reported spontaneous recovery of vision in about 40 % of 31 children with homonymous visual field defects. Matsuba and Jan (2006) found spontaneous improvement of visual acuity over two or more years in 97 of 194 children (50 %). Seventy-five of the children (38.7 %) did not show any change in acuity, while the remainder deteriorated (18, or 9.3 %); in 4 children, acuity could not be assessed properly. Children with better visual acuity values at follow-up also showed better cognitive outcomes. Furthermore, independent mobility was associated with higher visual acuity, indicating a favourable effect of vision on motor outcome. Similar observations had been previously reported by van Hof-van Duin et al. (1998) who found that visual outcome in children with CVI could be predicted by grating acuity at the age of 12–24 months in 27 out of 39 children (69.2 %). Watson et al. (2007) reported improvement of visual acuity in 49 % of 34 children and of contrast vision in 47 % of 39 children, but no relation was found between improvement in visual acuity and the aetiology of CVI.

Surprisingly, children with early more or less total bilateral occipital lobe injury in the first year of life may show recovery/preservation of ‘low’ vision in the central portion of their visual field, which allows them to detect a visual stimulus in motion, to fixate a stimulus or to follow a stimulus with eye and head movements (Werth 2006, 2007). An even more surprising picture emerges after loss of one occipital lobe, because – in contrast to adults – children may exhibit a nearly full visual field, at least for perception of light. This preservation of visual field contralateral to occipital injury may be explained by morphological reorganisation of retinal afferent pathways to the striate cortex and thus of transformation of cortical visual field representation (Muckli et al. 2009). Alternatively, light perception may also be mediated by subcortical structures, which are known to receive afferent signals from the retina and project to the striate cortex (Werth 2008). The latter hypothesis is supported by a study in 23 children with uni- or bilateral homonymous visual field defects with spared perception of moving visual stimuli in affected visual field regions (Boyle et al. 2005). Children can also recover from visual neglect; in contrast to adulthood, it seems that this disorder tends not to become chronic in children (Ferro et al. 1984; Trauner 2003; Kleinman et al. 2010).

De Haan and Campbell (1991) presented a 15-year follow-up of a 27-year-old female patient with developmental prosopagnosia with relatively preserved basic visuo-sensory functions which were largely intact and relatively well-preserved discrimination of a face and a ‘non-face’. In contrast, recognition of familiar faces was severely impaired, and facial expression recognition was difficult, so that the patient may not have been able to learn representations of faces. Joy and Brunsdon (2002) reported spontaneous improvement of visual face discrimination and identification and recognition in a 7-year-old boy with congenital prosopagnosia, who was assessed for the first time at the age of 4 years. In contrast, impaired visual recognition of familiar faces may not show any change (see also Ariel and Sadeh 1996; Sect. 4.​3.​8).

A particularly impressive example of spontaneous adaptation by highly efficient compensation strategies has been reported by Lê et al. (2002). The authors assessed in detail a 30-year-old man (SB), who suffered from bilateral posterior brain injury because of meningoencephalitis at the age of 3 years. Injury affected both ventral (occipito-temporal) pathways and the right dorsal (occipito-parietal) route, as verified by MRI. From his 6th to 16th year, SB had been in an institution for visually disabled children and young adults; during the ensuing 4 years, he followed a professional training. As acquisition of visual reading ability was not possible, he learned the Braille system, which he mastered fluently. He was unable to visually recognise stimuli, but had no difficulties with tactile recognition of the same items. What was remarkable with SB was the discrepancy between his severe CVI and his visually guided activities in everyday life, including sport activities; because of this mismatch, some teachers questioned his severe visual disability. He showed more or less normal visual-spatial orientation and navigation, learned how to ride a motorcycle and played as goalkeeper in an amateur football team. There were no impairments in cognition, language or motor functions. Detailed visual assessment revealed complete left-sided homonymous hemianopia without visual neglect, the distance binocular visual acuity for forms at a distance of 5 m was estimated 0.6. He showed impaired contrast sensitivity for middle and high spatial frequencies, cerebral achromatopsia and impaired form vision. Foveal light sensitivity was normal, and stereopsis was not impaired. Visual identification and recognition were severely impaired; SB could, however, ‘guess’ real objects with the help of characteristic (individual) features and properties. A similar outcome was found for faces. Although SB could correctly discriminate faces as identical or different in pairwise presentation, he was absolutely unable to visually recognise ‘familiar’ faces and also had difficulties identifying facial expressions. Reading was impossible, because SB also showed visual agnosia for letters (pure alexia). His visual imagination of colours was completely absent, while for other visual categories (objects, animals, faces), it was rudimentary. In sharp contrast to SB’s profoundly impaired visual identification and recognition, were his capacities in topographical orientation and navigation and in visually guided grasping. Sparing of just one (i.e. the left) dorsal visual processing route and the intensive spontaneous use of spared visual capacity (and possibly residual visual capacities belonging to the ventral routes) in everyday life had ensured that visual perceptual learning became sufficient to acquire remarkable visual-spatial skills. In situations, which primarily demanded visual-spatial capacities, SB behaved like a sighted person, while in situations that demanded visual identification and recognition, he behaved like a person who had become blind. Interestingly, SB never chose to be registered as visually impaired. SB’s visuospatial capacities in some ways resemble that of case DF, the patient who inspired the dual-route processing model of Milner and Goodale (2006). However, as Schenk (2006) has convincingly argued, spared visuomotor capacities in bilateral ventral route injury can alternatively be explained by redundancy of visuomotor control (see also Schenk and McIntosh 2010). Apart from the sparing and further development of visual-spatial and possibly also visual-cognitive skills, the case of SB tells us that visual development and adaptation to everyday life visual challenges require preserved (visual) learning capacity, including visual memory, attention and executive function, and a high level of motivation for visual information (visual curiosity). Thus, an optimal combination of functional brain plasticity, adequate (visual) environment and intensive practice of visuomotor actions and activities may explain SB’s significant improvements in useful vision and thus provide an excellent example of environmental- and practice-dependent plasticity of the visual system (see Chap. 1). Visuomotor experience over several years can manifestly enhance spontaneous adaptation to early CVI.

A positive interaction between vision and motor activities has also been reported by Pavlova et al. (2007), who examined the association between visual-spatial navigation and paresis in the upper and lower limb extremities in 14 preterm children with PVL at the age of 13–16 years. Children with upper limb paresis showed higher performance in a maze task than children with lower limb paresis. The authors concluded that children with intact lower limbs, i.e. with normal walking, also showed better visual navigation. This observation is underlined by Evenson et al. (2009) who found that reduced visual acuity accords a higher risk of motor problems in preterm children but not in term children small for gestational age.

In conclusion, despite many positive examples of spontaneous recovery of visual capacities and spontaneous adaptation, many children with CVI may exhibit persistent visual impairment (see Hoyt 2003), which may cause disability well into, if not during adulthood: in addition, persistent CVI may further affect overall health, self-perception, educational attainment, job choices and social interactions (Davidson and Quinn 2011). Thus, intervention measures are required as early as possible, to reduce the degree of visual handicap; to support an optimal visual, cognitive and social development of children with CVI; and to guarantee the best options possible for later life.

In the following sections, intervention strategies in children with CVI are described and discussed. Because scientifically proven programmes of intervention in children with CVI are not available, the strategies proposed represent recommendations of intervention. Of course, intervention in children with CVI should also be based on general principles of rehabilitation. Therefore, it seems helpful to first outline some fundamental issues that are relevant for visual rehabilitation in general, and for the rehabilitation in children with CVI in particular. The proposed intervention measures and strategies are exemplified by single-case reports in Chap. 9.

Direct intervention for specific visual impairments in children with CVI aims to ameliorate impaired visual capacities and compensate for irreversible visual impairments. For the individual child, it depends whether there is sufficient visual capacity in evidence, to work towards direct improvement, or whether compensation strategies will be sufficient. There is limited evidence for efficacy for direct intervention to improve vision in children with CVI (Williams et al. 2014), but lack of evidence for efficacy does not constitute evidence of lack of efficacy, and further systematic investigation in this area is required.

A good example is the work of Malkowicz et al. (2006) who showed that children with CVI can significantly benefit from systematic practice with discrimination and identification of visual stimuli.

The functional organisation of visual perception in the brain is based on parallel and serial processing and coding, organised within a form of hierarchy, in the sense that more complex (‘higher’) visual capacities depend, at least in part, on less complex, i.e. ‘lower’ visual capacities (see Chap. 2). For specific interventions, a sequence of steps emerges from the following functional organisation of the visual brain: