Multifocal VEP in children: its maturation and clinical application.

AIM To study the maturation of multifocal visual evoked potentials (multifocal VEP) in normal children between the ages of 5 and 16 years and to apply the results clinically in selected cases to the diagnosis of optic pathway diseases. METHOD 70 normal children were recruited from the community and multifocal VEP (Accumap ObjectiVision, Sydney, Australia) was recorded. The waveform of the evoked responses, the latency and amplitude were analysed. Using these data, an age matched comparison was made with three children with advanced optic nerve disease; two had optic nerve glioma and one had congenital glaucoma. RESULTS The full field amplitude did not correlate with age and varied greatly within each age group (coefficient of variability 28%). When scaled with respect to the background electroencephalogram the intra-age group variability decreased to 15% and a sigmoid relation was found between amplitude and age. The scaled amplitude remained largely unchanged till 11 years, between 11 and 13 years there was a rapid increase (40%), and remained stable thereafter. This relation was seen at all eccentricities tested. The latency decreased gradually with age and plateaued at 13 years. In the three children with vision abnormalities this test was able to detect scotomas consistent with their condition. CONCLUSION Multifocal VEP perimetry shows an age related maturation in the visual pathway, characterised by distinctive timeframe of development for amplitude and latency. It can be performed by children as young as 5 years of age and holds promise as a diagnostic test capable of documenting children's visual fields objectively, even before they are able to perform subjective field tests.