Crossed and uncrossed visual pathways are impaired differently in open angle glaucoma patients.

Recent electrophysiological evaluations, performed by pattern electroretinogram (PERG) and visual evoked potential (VEP) recordings, suggest that patients affected by open angle glaucoma (OAG) present a ret-inal dysfunction and a delay in neural conduction in the postretinal visual pathways (Parisi 1997). Although an impairment of the innermost retinal layers (ganglion cells and their fibres) is well documented (Quigley et al. 1995), only recently has an impairment of the lateral geniculate nucleus (LGN) been observed in animals in which experimental glaucoma was induced (Weber et al. 2000). Therefore, it is supposed that the abnormal visual cortical responses observed in glaucoma may result from both retinal impairment and the involvement at the LGN level. In our previous study (Parisi 1997), the VEP responses were derived by means of a single electrode placed over both occipital cortexes and therefore did not allow a separate evaluation of the neural conduction along the crossed and uncrossed fibre visual pathways. On the basis of recent evidence regarding postretinal involvement in glau-coma, the aim of our work now is to evaluate the neural conduction in crossed and uncrossed visual pathways in OAG patients.