Behavioural and electrophysiological measures of visual functions in children with neurological disorders.

The preferential looking (PL) technique, pattern visual evoked potentials (VEPs) and (simple) tests for visual field size were used to assess visual functions in 37 children with neurological disorders, ranging in age from 10 weeks to 15 years. PL acuities were obtained for 23 out of 32 patients tested (70%). Acuity was nearly always lower than normal, which often, but not always, was related to ophthalmological or neurological defects. Pattern VEPs were recorded in 7 patients. In 3 out of 4 patients, VEP 'acuity' was much lower than PL acuity, possibly due to spontaneous eye movements. One of two cortically blind children had positive pattern VEPs. Visual field defects were seen in 21 out of 23 children tested with a simple method using a pair of white balls. In only one-third of these, the field defects could have been predicted by the neurological and/or ophthalmological conditions. In several cases, field size appeared to be affected by spontaneous and/or latent nystagmus. A simplified perimeter has been found very useful with children from the age of 4 years onwards.