Pattern ERG and VEP maturation in schoolchildren.

OBJECTIVE: The maturation of the visual system has been studied with pattern electroretinograms (PERG) and pattern visual evoked potentials (PVEP) mostly in children under the age of 6 years. To address the question of maturation of the visual system in childhood and adolescence we investigated age-dependent PERG and PVEP changes in children aged 7-18 years. METHODS: PERG were recorded with skin electrodes attached to the lower eyelid, and PVEP were recorded with 5 electrodes. Visual stimuli, consisting of pattern-reversal 50' checks to full-field and to half-field stimulation, were applied to obtain macular (N70, P100, N145) and paramacular waves (P80, N105, N135). RESULTS: We found an age-dependent decrease (linear regression P<0.05) of PERG P50 amplitude and full-field PVEP P100 latency to monocular right and left eye stimulation, indicating central retinal and postretinal changes. In addition, waveform changes were found in responses to half-field stimulation. The paramacular wave N105 was typically enhanced in younger schoolchildren and diminished with age. The age-dependent decrease (linear regression P<0.01) of paramacular N105 amplitude indicated the increasing predominance of the macular structures of the visual system. CONCLUSIONS: Our findings suggest that central retinal and postretinal electrophysiological maturation persists throughout childhood. Age-dependent PVEP changes seem to correlate with the morphological and metabolic findings that maturation of the visual cortex continues until puberty and even later.

Dependence of visual evoked potentials on change of stimulated retinal area associated with different pattern displacements.

An attempt was made to distinguish between the effects of the moving edges and the change in the area of stimulated retina on pattern shift visual potentials, elicited by checkerboard pattern displacements varying through 0.25, 0.50, 0.75 and full pattern reversal. Twelve healthy subjects were stimulated binocularly with a horizontally orientated pattern (whole field 17 degrees, check size 28' of visual angle). Four of them were additionally presented with a diagonally orientated pattern. Two sets of 32 averages were taken for each stimulus condition and peak-to-peak amplitudes P50-N70 and P100-N140 were measured. The change of the stimulated retinal area is a quadratic function of the diagonally orientated pattern. The change in amplitude of P50-N70 fits well with the curve of the area change, but that in the amplitude of P100-N140 does not. Each of the amplitudes also seems to have a different orientation of hypothetical dipole vectors.