Objectives

This study was performed to compare the morphological maturation of the retina with its functional maturation in dogs.

Materials & Methods

A scotopic intensity series electroretinogram was recorded weekly following eyelid opening from seven dogs. For retinal morphology, tissues were fixed, plastic embedded and sections taken in a vertical plane through the optic nerve head. The thickness of retinal layers was measured at 8 regions across the retina using Neurolucida software (MicroBrightField).

Results

At 2 weeks of age, the peripheral retina was thicker than the central retina. The photoreceptor inner segments were present and a low amplitude ERG could be recorded. By 4 weeks of age the photoreceptor outer segments had formed but were not fully developed. The photoreceptor cell layer reached maximal thickness at approximately 7 week of age at which time maximal ERG responses were recorded. The photoreceptor cell layer became thinner by 16 weeks of age and this was reflected by a decrease in ERG amplitudes.

Conclusion

The ERG amplitudes correlate with the photoreceptor cell layer thickness. ERG achieves adult waveform as photoreceptor cell layer achieves maximal thickness.