Electroretinographic Responses of the Rabbit After X-Irradiation

¹ Radiation Research Laboratory and Department of Ophthalmology, University of Iowa Iowa City, Iowa.

The inhibitory effects of 250 KVP x-radiation on the electroretinographic response (ERG) of the rabbit were investigated. Rabbits were exposed (head only) to either a single dose ranging from 3,000 rad to 8,000 rad or to a fractionated dose, two doses of 3,000 rod each with an interval of 5 days. ERG responses of the dark adapted eyes of the rabbit were determined prior to exposure and at various intervals from 30 minutes to 1 week (2 to 8 weeks in a few cases) after irradiation. At 30 minutes after a dose of 5,700 rad or more, the b-wave was extinct and the a-wave nearly so. Both the a- and b-waves were extinct at 1 hour after 6,000 rad. No recovery was evident from the ERG responses obtained during the first 3 weeks after 6,000 rad. At 30 minutes after a dose in the range from 3,000 to 5,500 rad, the amplitudes of the a- and b-waves were inversely related to dose. In this dose range, various recovery patterns were indicated. After a single dose of 3,000 rad, no significant changes in the ERG response were found at 30 minutes, the amplitudes of the a- and b waves were about 60 per cent of the control mean at 1 day, and the amplitudes were in the normal range by the third week indicating a complete recovery. When a dose of 6,000 rad was fractionated, the amplitudes of the a- and b-waves were 10 to 15 per cent of the control mean at 30 minutes after the second dose of 3,000 rad. The amplitudes had increased to 32 to 36 per cent at 7 days after irradiation indicating some recovery.