Abstract
Abstract: :
Purpose: To compare multifocal ERG (mfERG) and multifocal VEP (mfVEP) in diagnosing optic nerve (ON) dysfunction and to determine optimal stimulus conditions. Methods: We recorded mfERGs and mfVEPs from 10 patients with ON disease. MfVEPs were recorded using two pattern reversal protocols with reversal every 13 or 26 ms, respectively. We compared root mean square (RMS) values of focal responses between corresponding field locations of each eye [1]. For mfERG stimulation we presented multifocal flashes at an interval of 67 ms interleaved with global flashes at 26 and 53 ms. For mfERG analysis we differenced amplitude estimates (scalar product) between right and left eye for a response epoch of 60-90 ms. For this epoch amplitude estimates were also calculated for each eye. Results: MfVEP: Among the two pattern reversal protocols the slow pattern reversal produced significantly higher amplitudes (Wilcoxon test). In 42% of regions of visual field loss the mfVEP showed RMS ratios of focal VEPs between the two eyes below 2 standard deviations of a normal control group. MfERG: For patients with maximum deviations of -35 dB in the Humphrey visual field, differencing right and left eye reproduced the field defects. In eyes with maximum deviation values higher than -35 dB, amplitude estimates without differencing the eyes matched the visual field defects. Both methods led to correspondence between Humphrey and mfERG results within a range of 2( 5). Conclusion: The mfVEP shows local loss of sensitivity but with poor coverage of the visual field. Depending on the degree of the visual field defect mfERG data have to be analyzed differently in order to show loss of ganglion cell function. To establish the mfERG as a method for reliable diagnosis of ON disease a quantitative analysis on larger patient populations will be needed. 1. Hood, Zhang et al (2000) IOVS
Keywords: 393 electrophysiology: clinical • 395 electroretinography: clinical • 557 retina: proximal(bipolar, amacrine, and ganglion cells)