Hyper-response of OP3 to systemic hyperoxia in the dark-adapted retina

We have demonstrated that the third wavelet (OP3) of the scotopic flash oscillatory potential (OP) complex shows a hyper-response during experimentally-induced systemic hyperoxia. The objective of the present study was to further evaluate and detail the time course of this enhanced retinal response.

Twenty healthy adults volunteered for this study. The OPs were recorded with a DTL-type electrode following pupillary dilation and retinal dark adaptation. Stimuli consisted of white flashes. The OPs were recorded at 8 points in time before, during and after breathing pure oxygen (O2). The arterial blood O2 saturation (SaO2), end-tidal CO2 (EtCO2), respiratory rate (RR), pulse rate (PR) and blood pressure (BP) were monitored throughout the experiment.

The amplitude of the OPs did not vary significantly across test conditions except for OP3, which increased with systemic hyperoxia and was still elevated by the end of the experiment. The SaO2 and RR increased, the EtCO2 and PR decreased, whereas the BP was not altered during O2 breathing.

This study provides further evidence indicating that the neural generators of OP3 display a unique hyper-reactivity to increased systemic O2 levels in the young healthy adult. Further studies looking at OP3 are still needed to determine if this unique behavior could serve as an index of altered oxygen level and retinal function in health or disease.