The prevalence of CVD in these prematurely born children is between 21-47 % (95 % CI), with a pattern similar to "dorsal stream dysfunction". Currently available perceptual tests appear to be unable to identify the specific pattern of problems noted in this group. Many studies have provided evidence of cognitive and intellectual dysfunction in prematurely born children, and it is possible that CVD is a contributor. The CVI inventory is a potential means of identifying and characterising the condition, which can be ameliorated with simple strategies.

Sir, Reliability of a question inventory for structured history taking in children with cerebral visual impairment Cerebral visual impairment (CVI) is the commonest cause of impaired vision in childhood. 1 Perceptual visual dysfunction from dorsal and/or ventral stream damage is often present [1][2][3][4] and is effectively elicited by structured history-taking. 1,2 To do this, we apply a 51-question inventory, in seven sections that requires validation. Case reportThirty-six consecutive children presenting to our clinic over 12 months with problematic CVI (mean age 10.8, range 5-16.5 years, SD 3.1) and 156 children (mean age 8.24, range: 4.5-11.6 years, SD 1.92) from seven mainstream primary schools (excluding those with poor reading skills, dyspraxia, autism, and other developmental and behavioural disorders) comprised patients and controls.Respondents completed a five-point Likert item scale, where questions were phrased such that lower-value answers of 'Never' (score 1) or 'Rarely' (score 2) denote normality, and 'Sometimes' (score 3) 'Often' (score 4), and 'Always' (score 5) denote impairment.Scores were summated for each section. Internal reliability was tested with Cronbach's a, 5 comparing the variance in response for individual questions, to the variance in response for the whole section. Intra-rater reliability was tested by 19 consecutive families completing the inventory twice, one week apart. The intra-class correlation was computed on total coefficient scores. Analyses were performed using SPSS (Version 15) and Minitab (Version 16).Results are shown in Table 1. Forty-nine of the 51 questions showed consistency and reproducibility in the control population; the responses of 'often' and 'always' not occurring, apart from two questions. Patient responses for all seven subsections indicated poorer visual performance than for control children. The intraclass correlation score was 0.98, indicating good intra-rater agreement. CommentThis, now validated, structured history-taking inventory helps characterise high functioning CVI, 1,3,4 and is a practical tool that is used by colleagues internationally. Two questions concerning visual attention were found to be nonspecific and have been reworded. 1 AcknowledgementsThis study was partly funded by Medical Research Scotland Grant Study Number: 106FRG.

The classical model of how the human visual system works is that image data are transferred from the eyes to the occipital cortex where the picture is "seen". Damage to the parts of the brain serving vision causes visual field impairment and reduced visual acuities. However, additional impairment of higher visual processing is common and may go unrecognised.Two higher visual pathways have recently been described, the dorsal and ventral streams. The dorsal stream connects the occipital lobes and posterior parietal lobes. It serves to appraise the whole scene, and perceive elements within the scene. It facilitates visual guidance of movement, by interacting with area V5 of the middle temporal lobes, or motion perception centre. It is automatic, immediate and unconscious. It is 'on line' and is not memory based. Damage impairs visual guidance of movement (optic ataxia) and visual search. The ventral stream links the occipital and temporal lobes, which contain the "image libraries". Recognition of faces, shapes, objects and routes, is attained by matching incoming data with "library data".Dorsal stream dysfunction results from posterior parietal damage and is associated with cerebral palsy, periventricular white matter injury, premature birth, hydrocephalus and Williams' syndrome, and similar visual difficulties are becoming apparent in children with autistic spectrum disorder. Ventral stream dysfunction is less frequent and usually accompanies dorsal stream dysfunction. It is not uncommon in children with hydrocephalus.A specific disorder of dorsal stream dysfunction is emerging, comprising difficulty handling the complexity of a visual scene (of varying degree) with impaired visual guidance of the limb movement (optic ataxia). Commonly, but not always this is associated with reduced visual acuities and visual field impairment, and occasionally with impaired recognition of people (which could be called "dorsal stream dysfunction plus").