Abstract
Abstract: :
Purpose:We compared immaturities of post–receptoral function, represented by the ERG oscillatory potentials (OPs), to photoreceptor immaturities derived from the a–wave. Both rod and cone mediated responses were studied. Methods: ERG responses to a 5.0 log unit range of full–field blue flashes were recorded from dark–adapted subjects. Responses to a 2.4 log unit range of red flashes on a rod–saturating white background were also recorded. Four–week old (N=22) and 10–week old (N=38) term born infants and adult controls (N=28) were tested. The records showing a– and b–waves were filtered (75–300 Hz) to demonstrate the oscillatory wavelets. Amplitude and implicit time of OPs were examined as a function of flash intensity and were evaluated for variation with age. Photoreceptor sensitivity (S) and saturated amplitude (Rmax), derived from the a–wave, were also evaluated for variation with age. Results: For both rod and cone mediated responses, the implicit time of each OP wavelet decreased with increasing stimulus intensity and increasing age; these stimulus/response functions for the three age groups were parallel. OP amplitudes in infants varied little with stimulus intensity, whereas those of adults increased with increasing intensity. The amplitudes of the infants’ cone mediated OPs were closer to the average adult amplitudes (approximately 50% of the adult value) than the corresponding rod mediated OPs (approximately 20%). The infants’ photoreceptor response parameters, S and Rmax, were also more adult–like for cones than for rods. Conclusions:We conclude that the relative immaturities of rod and cone mediated post–receptoral processes, represented by the OPs, are similar to those of the photoreceptors.
Keywords: electroretinography: non–clinical • visual development: infancy and childhood • photoreceptors