Abstract
Abstract: :
Purpose: To determine the effect of hypoxia on the human multifocal electroretinogram (mfERG) and multifocal oscillatory potentials (mfOP). Methods: In 10 eyes of 10 healthy volunteers, mfERGs were recorded during hypoxia and normal oxygenation. Hypoxia was induced by inhalation of a 10% O2 and 90% N2 gas mixture, reducing mean blood oxygenation from 98.8 to 69.4%. To insure a stable systemic level of oxygenation, patients breathed the gas mixture for a period of 5 min before and during the recording period. 61 retinal areas were stimulated by a Veris 4 system and each pseudorandom multifocal flash was followed by 3 dark frames to allow derivation of oscillatory potentials. First– and second–order ERG kernels were derived from each area and analyzed for averages from 5 concentric rings. To test for response asymmetries, an additional analysis was made for averages of a central and 8 peripheral regions (mixed–model analysis, SAS Institute). Results: Hypoxia significantly decreased mean first–order P1 and N2 amplitudes averaged from 5 concentric rings: P1 amplitudes from ring 1(central response) decreased by 36.1% (51.3 nV/deg2) and amplitudes from ring 2–5 decreased by 18.9 to 25.6%. The mixed–model analysis confirmed this effect. Both analyses showed a larger effect of hypoxia on central responses than on peripheral responses. Hypoxia reduced the mean amplitude of mfOPs. Conclusions: The mfERG is highly sensitive to moderate hypoxia. Sensitivity to hypoxia varies significantly with retinal eccentricity.
Keywords: electrophysiology: non–clinical • hypoxia • macula/fovea