Widefield Multifocal Electroretinography (WF–mfERG) to Study Radial Optic Neurotomy for Central Retinal Vein Occlusion (CRVO)

Abstract

Abstract: : Purpose: A pilot study to investigate the effect of pars plana vitrectomy (PPV) and radial optic neurotomy (RON) on P1 amplitudes and implicit times for CRVO using WF–mfERG. Methods: The multifocal electroretinograms were recorded using a custom built electrophysiological system, which stimulated 90 degrees of the visual field. Wide field stimulation was achieved by using a digital polysilicon projection system. The stimulus array contained 61 empirically scaled hexagons. Each hexagon alternated between black and white (97% contrast) controlled by a binary m–sequence. Five patients underwent PPV and RON for CRVO using a nasal approach under standard conditions. Five age and sex matched patients with CRVO were recruited for the control group. All patients were followed up over twelve months. Results: Postoperatively, there was no improvement in logMAR visual acuity for the ischaemic group, and an increase of 0.43 for non–ischaemic CRVO. There was no significant improvement in implicit timing or P1 amplitude following PPV and RON for ischaemic CRVO. The implicit timing worsened by 5ms after surgery for the non–ischaemic CRVO, then resolved to preoperative levels by six months. The P1 amplitude and implicit times for the ischaemic CRVO control group were worse in contrast to the non–ischemic group where responses improved. Conclusions: Pars plana vitrectomy and radial optic neurotomy for ischaemic CRVO had no significant effects on P1 amplitude or implicit timings compared with the control group. Non–ischaemic CRVO may improve without intervention.

Keywords: electroretinography: clinical • vitreoretinal surgery • retina: distal (photoreceptors, horizontal cells, bipolar cells)