Abstract
Abstract: :
Purpose: Scattering light from the optic nerve head and myelinated nerve fibers can disturb investigations with multi focal ERG (mfERG) in the rabbit eye. We wanted to test the feasibility of detecting a localized lesion in the rabbit retina using the mfERG. Methods: Ten animals aged 5 months underwent surgery consisting of a two–port vitrectomy with subsequent retinectomy. The area of removed retina was approximately 1.5 disc diameters in size, located in the visual streak nasal to the optic nerve head. Both eyes were investigated with mfERG preoperatively and the operated eye also at 1,3, 7, 13 and 21 weeks postoperatively. A Burian–Allen bipolar contact lens with built–in infrared emitters was used to visualize the retina during the recordings. The average of the trace array amplitudes in the lower nasal and temporal quadrants were calculated and statistically analyzed at the different time intervals. Results: In almost all cases, the optic nerve head, medullary ray and retinectomized area were visualized using the infrared .The highest amplitudes were found in the area corresponding to the myelinated nerve fibers and optic nerve head. There was no statistical difference between the average amplitude in the nasal and temporal lower quadrants preoperatively nor in the normal left eyes used as control. At 1 and 3 weeks postoperatively, amplitudes were generally reduced over the entire stimulated area. After 7 weeks the amplitudes in the lower temporal quadrant were higher than those found at earlier postoperative examinations, whereas the levels in the nasal part (including the retinectomy) remained low with a statistical difference between the mean amplitude of the lower quadrants (p<0.05). At 13 weeks this difference was even more pronounced (p<0.006). Conclusions: This study shows that retinal lesions with the size of 1.5 optic nerve heads, located in the visual streak, can be detected in the rabbit eye using the mfERG. Scattering light probably causes the high amplitude level over the area of the myelinated nerve fibers.
Keywords: retina • electroretinography: non–clinical • imaging/image analysis: non–clinical