Abstract
Abstract: :
Purpose: To evaluate the neural conduction in crossed and uncrossed visual pathways in patients with ocular hypertension (OHT). Methods: 15 patients (mean age 59.1 ± 6.8 years) affected by OHT (IOP≷22 mmHg, Humphrey 24-2 with Mean Deviation - MD- < - 2 dB) were enrolled. They were compared to 15 age-matched controls. In OHT patients and control subjects, Visual Evoked Potentials (VEPs) were recorded using full field checkerboard patterns (the check subtended 15' of visual arc; contrast 80%) reversed at 2 Hz. The bioelectrical cortical responses were recorded simultaneously in the homolateral visual cortex (HC) and in the contralateral visual cortex (CC), with respect to the stimulated eye. The differences between OHT patients and controls were evaluated by ANOVA, and linear regression analyses were adopted to establish the correlation between perimetric (Humphrey 24/2) and VEP parameters. Results: In OHT patients, the VEP P100 implicit times observed in HC and CC were both significantly (P<0.01) delayed when compared to those of controls. In all OHT patients we found an asymmetry in VEP responses obtained in HC and CC with VEP P100 implicit times longer in CC than in HC. The inter-hemispheric differences (ID: P100 implicit time in HC - P100 implicit time in CC) were significantly higher in OHT patients than controls (-3.16± 1.80 msec and 1.16±1.04 msec, respectively, P=0.001). In OHT patients we observed an MD hemi-field difference (difference between nasal and temporal MD values) higher than that of controls (-0.82± 0.80 dB and 0.04± 1.03 dB, respectively, P<0.01) and significantly correlated with the ID (r: 0.837, P0.05) but significantly correlated with the ID (r: 0.667, P=0.006). Conclusion: The observed asymmetry in the bioelectrical visual cortical responses and in the visual hemi-field parameters suggests that crossed visual pathways could be more impaired than uncrossed visual pathways in OHT patients.
Keywords: 393 electrophysiology: clinical • 511 perimetry • 621 visual cortex