The Porcine Multifocal Electroretinogram (mfERG) in Healthy Eyes and in Eyes With Surgically Induced Retinal Traumas

Abstract

Abstract: : Purpose: We have previously presented a method to obtain mfERG recordings during continuous fundus monitoring in the domestic pig, and electrophysiologically identified the presence of a high–cone–density area (visual streak) in the porcine retina (Kyhn MV et al, ARVO abstract 4247, 2004). We now present the normal mfERG in the domestic pig, and the ability to detect a surgically induced localized retinal trauma with the mfERG. Methods: 12 domestic pigs underwent mfERG recordings on both eyes at baseline, and after 1 and 6 weeks. On the left eyes surgery was performed after the initial baseline recording. 3 pigs underwent a simple vitrectomy, 3 pigs had a vitrectomy and an induced, local retinal detachment (bleb) in the visual streak area. Three pigs underwent vitrectomy, bleb formation and diathermia in the center of the bleb. The remaining 3 pigs had an additional retinotomy performed. After the last examination, 6 weeks postoperatively the pigs were euthanized. The treatment of the pigs followed the ARVO resolution for the use of animals in ophthalmic and vision research. Results: In the untreated eyes we recorded mean component amplitudes in the visual streak area of N1 of –6,2 nV/deg², P1 of 12,2 nV/deg² and N2 of –9,2 nV/deg². We detect no significant difference between the baseline (p>0,1), 1 and 6 weeks recordings (p>0,05) regarding as well the implicit times as the amplitudes. In our surgically manipulated retinas we find that a simple vitrectomy, a local retinal detachment with or without additional diathermia in the visual streak area does not significantly influence the implicit times (p>0,05) or the amplitudes (p>0,1) of the mfERG components after 6 weeks. A retinotomy, on the other hand, significantly increases the implicit times of component P1 and N2 (p<0,04) after 1 and 6 weeks, while the amplitudes are significantly reduced after 1 week (p<0,05) but normalized after 6 weeks (p>0,1). Conclusions: We have identified the rage of component implicit times and amplitudes in the normal porcine retina. Further more we show that the performance of simple and frequently used surgical procedures does not influence the component implicit times or amplitudes after 6 weeks of observation. However, a retinotomy prolongs the component implicit times with no sign of regression after 6 weeks of observation.

Keywords: electroretinography: non-clinical • electrophysiology: non-clinical • retina