Hypobaric hypoxia reduces the amplitude of oscillatory potentials in the human ERG.

PURPOSE

To explore the retinal functions in healthy volunteers during acute hypoxic exposure, applying a set of electrophysiological tests.

METHODS

Standard electroretinograms (ERGs) of the retina (rod-(scotopic) ERGs, cone-(photopic) ERGs, maximal responses and oscillatory potentials (OPs)) and 30-Hz flicker ERGs were recorded according to ISCEV (International Society of Clinical Electrophysiology of Vision) recommendations in 14 healthy volunteers during a 15-min exposure to a simulated altitude of 5500 m.

RESULTS

The mean arterial oxygen saturation level was significantly reduced (P < 0.001) during the hypobaric challenge. It returned to the normal level very shortly after the end of the hypoxic exposure. No significant change in the latency or amplitude of the slow components of the ERG was found in any recording. The OPs of the ERG, however, revealed a significant decrease in amplitude during hypoxic exposure. Both OP1 and OP2 amplitudes were significantly different (P < 0.05) from the baseline values during hypoxia. Partial recovery of these waves occurred after termination of the hypoxia.

CONCLUSIONS

These results appear to support the notion that the inner layers of the retina presumed to be the main source of the OPs, display the highest sensitivity towards circulatory and/or hypoxic challenges.