Investigation Of Multifocal Visual Evoked Potentials And Multifocal Electroretinogram In Amblyopic Children

ObjectiveTo study the characteristic changes of multifocal VEP and multifocal ERG inanisometropic amblyopia and strabismic amblyopia, and a simultaneous recording technique was used to study the changes in retinocortical times, to evaluate the possible mechanism of amblyopia. MethodsThe multifocal pattern VEP and multifocal flash ERG of both eyes of 23 anisometropic amblyopes, 20 strabismic amblyopes and 30 normal subjects were recorded by VERIS SciencerM 4.2 multifocal visual evoked response imaging system. The latencies and amplitudes of P waves were analysied. Changes in different retinal area including the hemifields , quadrants , naso-temporal and different eccentricities were investigated by comparing the amblyopic eye, the fellow eye of the patients and the normal eyes.Twenty four anisometropic amblyopes and another 30 normal subjects were investigated by simultaneous recording of mVEP and mERG. Pattern and Flash stimulus were adopted separately. Also the latencies and amplitudes of P waves were analysied. For multifocal flash recording the first-order and the second-order kernel signals were analysed while for multifocal pattern recording only the first slice of second-order kernel was analysed. Retinocortical times were also compared. Responses in hemifields and different eccentricities were also analysed to investigate the changes of amblyopia in different retinal areas.Results1. Results of mVEP and compared with those of mERG.a) At six eccentricities the N[P and PN2 amplitudes of mVEP and mERG of the amblyopic eyes were reduced compared with the fellow eyes and the normal eyes, while there were no significant differences between the fellow eyes and the normal. In amblyopic eyes the latencies of mVEP were markedly prolonged while no changes of the mERG latencies were found in amblyopic eyes. In upper and lower hemifields, the mean mVEP and mERG amplitudes of the amblyopic eyes were lower than those of the fellow eyes and the normal eyes, while the mVEP amplitudes of the fellow eyes also were lower than the normal. Prolonged latencies of responses in amblyopic eyes were only found in mVEP but not in mERG. In esotropic amblyopia, the mean amplitude of mVEP in the nasal retinal hemifield was smaller than that in the temporal retinal hemifield. While no difference between the nasal and temporal retinal hemifields was found in mERG. While in anisometropic amblyopia, there were no differences between the nasal and temporal retinal hemifields in mVEP, but the mERG amplitudes in the temporal retinal field in amblyopic eyes were reduced compared with those in the nasal retinal field.b) The relationship between the abnormality of the mVEP and mERG waveforms and the eccentricities were studied. The abnormality of the mVEP waveform in amblyopia decreased with the eccentricity increased, such changes in mERG were only found in strabismic amblyopia. In anisometropic and strabismic amblyopia, the abnormalities of mVEP were larger than those of mERG in almost all eccentricities.c) The abnormalities of mVEP were correlated with the damage of visual acuity of the amblyopic eye in all six eccentricites. The worse the visual acuity ofthe amblyopic eye, the larger the abnormality of the mVEP. But there were no such correlations in mERG .d) Distribution of the cone cells and the ganglion cells were compared respectively with the first order and the second order response densities of mERG in normal subjects, we found the distributions were different. The results questioned the previous view.2. Results of simultaneous recording of mVEP and mERGa) In each eccentricity the amplitudes of simultaneous recording of multifocal pattern ERG and VEP and the second order kenerl of simultaneous recording of multifocal flash ERG and VEP were reduced in anisometropic amblyopia. Only the latencies of the mVEP were prolonged. Same results were found in the upper and lower hemifields. For the first order kenerl of simultaneous recording multifocal flash ERG and VEP, the respons...