Modulation of the scotopic electroretinogram and oscillatory potentials with systemic hyperoxia and hypercapnia in humans.

PURPOSE

Systemic hyperoxia reduces blood flow to the retina while systemic hypercapnia has the opposite effect. However, the effect this modification in blood flow has on neuroretinal function in humans has not been documented yet. The purpose of this study was to evaluate the effect of pure oxygen and carbogen breathing on scotopic electroretinograms (ERGs) and oscillatory potentials (OPs) in humans.

METHODS

Thirty-five healthy adults volunteered for this study. The ERGs and OPs were recorded: 1) during room air breathing, 2) after a period of pure oxygen (O(2)) or carbogen breathing, 3) in room air just after the flow of gas was interrupted, and 4) 10 minutes after the end of the gas administration.

RESULTS

The amplitude and latency of the a- and b-waves were not altered during systemic hyperoxia. The amplitude of OP3 increased during hyperoxia while the amplitude of the other OPs was not altered. The latency of all OPs remained stable throughout the O(2) session. Ten minutes after the end of pure O(2) breathing, the a- and b-wave latencies were delayed. No change was found in the amplitude of the a-wave during the carbogen session that increased the end-tidal carbon dioxide by 7.1%, whereas the b-wave was reduced ten minutes after the end of carbogen breathing. The amplitude of OP5 was reduced during carbogen breathing, as well as 10 minutes later. The amplitude of all other OPs, as well as the latencies of all ERG and OP components remained stable throughout the carbogen session.

CONCLUSIONS

Breathing pure O(2) or carbogen did not compromise retinal function in any major way, likely due to adequate retinal and choroidal regulatory mechanisms. Further investigations are required to better delineate the impact and temporal characteristics of such physiological challenges on retinal function.