1990 Volume 9 Issue 1-2 Pages 33-38
Postnatal development of the visual system in dogs was investigated by funduscopy and by electrophysiologcal and other methods during the first 6 months after birth.
Opening of the eyelids was observed between 9 and 12 days of age in beagles. A small negative wave of visual evoked potentials (VEP) was first recognized at 12 days of age. The a-wave of the electroretinogram (ERG) appeared a little later, between 16 and 19 days of age. The b-wave was recorded between 18 and 22 days of age. The amplitude of both the a- and b- waves increased rapidly between 3 and 6 weeks of age. The oscillatory potentials (OPs) were noted between 23 and 25 days of age. Characteristic OP waves, however, appeared after 6 weeks of age. The latency time in a-and b-waves shortened markedly between 3 and 4 weeks of age, and these waves exhibited a similar pattern in every examination thereafter. Measurement of the intraocular tension revealed a value of 25 mmHg at 17 days of age, this value was very close to that of adult dogs.
As accidental changes encountered during the study, retinal hemorrhage in the fundus was noticed after a single strong stimulus or repeated flash stimuli in VEP or ERG examination during the neonatral stage of 21 to 26 days of age. Such retinal hemorrhage appeared in 4 out of 19 neonates. It appeared bilaterally in one animal and unilaterally in the others. The hemorrhage was transient and the exudate in the vitreous body was absorbed 6 to 50 days later. Opacity of the cornea and neogenesis of vessels were also observed in one animal after wearing the contact lens for the ERG test.
