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E. C. Campos, M. E. Scarale, N. Balducci, M. Fresina, V. Parisi; Electrophysiological Detection of Delayed Post-Retinal Neural Conduction in Amblyopia. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4750.
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Simultaneous recordings of pattern electroretinograms (PERG) and visual evoked potentials (VEP) allow us to separate a macular dysfunction from a delay in neural conduction along post-retinal visual pathaways1. Our work aims to evaluate the macular function and the neural conduction along the visual pathways in amblyopic patients.
25 anisometropic amblyopic patients [mean age 7± 1.9 years; Visual Acuity (VA): 0.44± 0.27 LogMAR in amblyopic eyes (AE), 0.023± 0.067 LogMAR in sound eyes (SE)] and 25 age-similar controls (AS eyes, VA of 0.0± 0.0 LogMAR in both eyes) were enrolled. In AE, SE and AS eyes, simultaneous PERG and VEP were recorded in response to checks reversed at the rate of 2 reversals/s stimulating macular or extramacular areas (the checks edge subtended 15’ and 60’of visual arc respectively) 2.
Non significant differences (ANOVA, p>0.01) in PERG and 60’ VEP responses and in 60’ Retinocortical Time (RCT; difference between VEP P100 and PERG P50 implicit times) between AE, SE and AS eyes were observed. AE eyes showed a significant (p<0.01) increase in 15’ VEP P100 implicit time and in 15’ RCT with respect to the values observed in SE and AS. In amblyopic patients the interocular difference in VA was significantly (Pearson’s Test, p<0.01) related to the interocular difference in 15’ VEP P100 latencies and in 15’ RCT.
Our amblyopic eyes showed abnormal visual cortical responses only when the macular area is stimulated (increase in 15’ VEP P100 implicit times). This functional impairment, in presence of a normal macular function (15’ PERG responses similar to control ones), can be ascribed to a delay in post-retinal neural conduction (increase in 15’ RCT). The interocular differences in post-retinal neural conduction were correlated to the interocular differences in visual acuity.1Celesia GG, Kaufman D, IOVS, 1985;26:726-35.2 Tomoda H, Celesia GG, Toleikis SC. Electroencephalogr Clin Neurophysiol 1990;80:81-88.
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