550 



WERNER K. NOELL 



Fig. 7. Decline of the ERG of close and distant eye with 2,000 kvp irradiation. 

 The ordinate gives the ERG amplitude in millimeters of deflection as recorded by ink- 

 writer. The ERG decline of the distant eye starts at the time of termination of the 

 irradiation. The dose delivered to the distant eye is insufficient to produce complete 

 ERG disappearance, in the early postirradiation period. 



diminution, if it occurred at all. became apparent within 2 horns after 

 irradiation. In relation to the fairly even distribution of absorbed dose of 

 2,000 kvp irradiation over the retina, the effectiveness of the x-rays tended 

 to follow the all-or-none rule; that is, if effective at all, 2,000 kvp radiation 

 generally produced a sudden decline of the ERG to at least the 50% level. 

 In contrast, 250 kvp radiation produced graded amplitude reductions, 

 ranging from slight to severe, in accordance with the steeper gradient in 

 absorbed dose of this radiation over the retina. 



There was no recovery from any ERG decline which developed within 

 30 minutes after irradiation. If the ERG disappeared immediately or within 

 a few hours after exposure, reappearance of a measurable response did not 

 occur (Fig. 9). This lack of recovery differentiates the x-ray effects 

 from those of iodoacetate and oxygen at high pressure. Recovery from ERG 

 disapperance is observed following these poisons, unless their doses are 

 excessive (Noell, 1959). 



Transient effects in our experiments were a slight fall in ERG amplitudes, 

 developing slowly within 2 hours after irradiation, and an accelerated b-wave 



