Maturation of the retina of the canine neonate as determined by electroretinography and histology.

Retinal potentials were obtained by electroretinography from birth to maturity of dogs. Amplitudes, time latency, and flicker fusion frequencies under scotopic conditions were compared to the histologic development of the retina. There was no electroretinogram (ERG) recorded during the 1st week of life, but in the 2nd week, a small negative wave (not exceeding 5 microV) was detected. Small ERG waveforms appeared in dogs at 3 weeks of age; these markedly increased in amplitude and latency between the 3rd and the 4th weeks of age. Additional changes in the ERG amplitudes were evident in the 5th to the 8th weeks of life approximating amplitudes of the adult dog. Similarly, the greatest changes in flicker fusion frequencies occurred between the 3rd and the 5th weeks and the 7th and the 8th weeks. Latency of the a-wave indicated little change in the age groups studied. The greatest decrease in latency occurred in the b- and c-waves between the 3rd and 5th weeks of age. The rod and cone inner and outer segments were first observed microscopically in the 3rd week after the dogs were born. Further differentiation of the rod and cone segments and other retinal layers occurred from the 5th to the 8th weeks.