Electroretinography (ERG) alterations following positional changes in gas-filled eyes after a vitrectomy

Recording electroretinograms (ERGs) in eyes with intraocular gas tamponade is difficult, and the mechanism remains unclear. We evaluated the effect of intraocular gas on ERGs by comparing recordings at different body positions.

This study included 31 patients who underwent vitrectomy with sulfur hexafluoride (SF6) or air tamponade at Hirosaki University (between May 2023 and October 2024). The patients included those with retinal detachment (25 patients), macular holes (4 patients), and epiretinal membranes (2 patients). ERGs were recorded using skin electrodes when approximately 50% of the vitreous cavity was filled with the intraocular gas. ERGs were recorded in sitting, supine, and face-down positions. Amplitudes and latencies of the LA 3 b-wave and LA 30 Hz were compared using the Wilcoxon signed-rank and Friedman tests.

In the gas-filled eyes, amplitudes in the face-down position were smaller, and latencies were longer than those in the other positions (p < 0.05). Median amplitudes in the gas-filled eyes in the sitting, supine, and face-down positions were 20.4, 19.5, and 10.1 µV for LA 3 and 14.4, 15.5, and 7.11 for LA 30 Hz, respectively; median latencies were 32.5, 33.0, and 34.3 ms for LA 3 and 30.8, 30.0, and 34.3 for LA 30 Hz, respectively.

ERG amplitudes were reduced and latencies were prolonged in the face-down position, which may be attributed to a larger retinal area being covered by intraocular gas. The gas acts as an insulator, and the gas-covered retina may not effectively generate or transmit electrical signals.