Isolated occipital injury in children is fortunately rare. The outcome tends to be primarily one of impaired vision. In our experience, it is more frequently acquired than congenital in origin, but can be due to focal brain injury during the first year of life. As discussed in Chap. 4, skills learned through vision that predate the brain injury may well remain unaffected, so that the later the injury, the greater the range of prior skills to seek and capitalise upon during rehabilitation.

The clinical features of focal occipital injury include reduction in visual acuity, contrast sensitivity and colour vision. Visual field impairment tends to affect the different quadrants to different degrees so that one quadrant or one half of the visual field may function better than the others. This is usually set against a background of overall visual field constriction. A common pattern is one of limited preservation of the left or right upper quadrant of the visual field. Visuomotor skills may be impaired, but in some cases are spared, resulting in the paradoxical behaviour of the affected child being fully mobile despite profound visual impairment (see letter to parents in Sect. 6.​5). This type of vision is known as ‘blindsight’ in the adult literature (Weiskrantz 2004; Cowey 2010). Children affected in this way are usually able to compensate for, or supplement their lack of visual recognition by means of tactile skills (Boyle et al. 2005). In cases where the child has learned to understand and appreciate form and shape, and/or the alphabet, prior to brain injury, they can have the remarkable ability to move a finger over a drawing of a shape or letter (not embossed) and thereby recognise it haptically, through the nature of their movement, despite not being able to do so through vision. As reported in adults, the additional skill of imagining that they are moving their finger over the image can be developed and employed to learn to recognise shapes and even letters of the alphabet, through imagined finger following, or ‘pantomiming’ (Goodale and Milner 2013). This observation has the potential to be formalised as a rehabilitative strategy in cases of this nature. In cases with progressive recovery, in whom visual acuity is gradually regained, visual agnosia may continue to be a limiting factor.

Profound visual impairment can accompany cerebral palsy. This can be due to optic atrophy, but in many cases the optic atrophy is limited, and the pupils react briskly. In these cases, cerebral visual impairment is suspected. Affected children may show no evidence of vision or may manifest intermittent and often fatiguable visual responses (Brodsky 2010). Light gazing is seen in a number of cases (Jan et al. 1990). Some children show intermittent reflex mouth opening in response to an approaching spoon from the side, but do so less often when the spoon approaches from straight ahead (Boyle et al. 2005). Parents and caregivers sometimes describe a positive response to a silent smile. This is akin to affective blindsight. (Affective blindsight is the phenomenon seen in some adults blind due to bilateral severe occipital damage, who respond to facial expressions conveying emotion, despite their low or absent vision (Andino et al. 2009)). Visual function as measured by visual evoked potentials (VEPs) may in some cases be enhanced under low luminance conditions (Good and Hou 2006), and parents may comment on their child’s visual attention being greater in conditions of low lighting. In other children, no visual evoked potentials are identifiable at the normal latency of around 100 ms, yet a very small signal can be detected at 60–70 ms, suggesting that it arises from subcortical areas (Boyle et al. 2005). Additional damage to thalamic structures serving reflex attention tends to be associated with the most profound forms of CVI in which even this form of ‘primitive’ visual reflex may not be in evidence.

Another form of visual behaviour is for visual attention to become manifest when pattern and clutter have been completely removed. For some children, this can be achieved in a sensory room, where they become more attentive. When there is a single item to see (whether a moving light or the focally lit face of the child’s mother), the child’s visual attention can improve remarkably. This may also in part relate to improvement in visual behaviour in low light levels. A similar alternative strategy (that can prove effective even in some children who fail to respond in a sensory room) is to surround the affected child and carer by a monochromatic coloured and illuminated suspended curtain (Little and Dutton 2014). Following this approach, children who have sat head down and inattentive in the long term have been reported to start to look around with evident excitement and pleasure. These visual behaviours are suggestive of underlying hitherto unidentified visual disorders similar to Balint syndrome (masked by accompanying cerebral palsy and intellectual dysfunction) and also indicate that profoundly impaired visual guidance of movement (optic ataxia) may compound any associated cerebral palsy. This potentially necessitates physiotherapeutic efforts to encourage and support tactile supplementation of visually guided reach, initially while enclosed by a tent in this way. Children whose attention has been ‘woken up’ by being enveloped in monochromatic colour for half to one hour period during the day can continue to manifest this improvement outside the tent.

The question inventory shown in Table 8.1 below provides information that has been shown to relate closely to estimated vision using preferential looking methods and vision evoked potentials (McCulloch et al. 2007). It can therefore be used to good advantage, particularly for children who are unable to cooperate at the times of assessment.