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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.

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Vision is sensitive to first-order luminance modulations and second-order modulations of carrier contrast. Our knowledge of the temporal properties of second-order vision is insufficient and contradictory. Using temporal summation and reaction time paradigms, we found that the type of visual noise (static or dynamic) determines the temporal properties of the responses to luminance and contrast modulations. In the presence of static noise, the temporal responses to both types of modulation of low and higher spatial frequencies were transient. When dynamic noise was used, the temporal responses to luminance and contrast modulations of higher spatial frequencies were sustained. At low spatial frequency, however, luminance modulations elicited transient responses, while contrast modulated dynamic noise produced sustained responses. The reaction times to near-threshold contrast modulations of low spatial frequency were slower than those to first-order patterns and they did not significantly differ at modulations of higher spatial frequency. The results suggest that the temporal characteristics of first-stage linear filters which feed the second-order pathway may determine the temporal responses to contrast modulated noise.

We studied visual evoked potentials (VEPs) elicited by second-order contrast modulations of binary dynamic noise and first-order luminance modulations. Using a 3-point Laplacian operator centred on Oz, we found that contrast modulations of both low and higher spatial frequencies elicited a negative component whose latency was about 200 ms. The latency of this component was significantly longer than that of the early Laplacian components to first-order luminance modulations. These findings could be due to slower first-stage linear filters and additional processing stages of the second-order pathway. The topographical analysis of scalp recorded VEPs to central and half-field stimulation has suggested that the responses to second-order patterns are likely to be generated by neuronal structures within the primary visual cortex which may have inputs from extrastriate neurons via feedback connections.