Assessment of visual function in MS patients: comparative study of some diagnostic tests

Optic pathways are frequently involved in Multiple Sclerosis (MS). However, in some cases the involvement is asymptomatic or gives rise to only slight visual disturbances without alterations of visual acuity or of clinically evident visual field defects. In these cases several diagnostic tests permit an objective evaluation of the visual dysfunction. The aim of this study is to compare the value of contrast sensitivity test (CST), pattern reversal visual evoked potential (VEP), ophthalmoscopy, Goldmann perimetry in 45 MS patients with normal visual acuity. Examination of contrast sensitivity was carried out with a simple two-alternative forced choice test estimating the spatial frequency of 4 cycles/degree. The VEP was performed with a pattern reversal checkerboard at a spatial frequency of 1 and 2 cycles/degree. Fundus examination was abnormal in 12 patients; visual field defects were detected in 16 patients. 32 patients (71.1%) had abnormal CST in one or both eyes. VEP for the 30' checks was abnormal in 32 cases (71.1%) and that for the 15' checks in 36 cases (80.0%). All but 4 patients (91.2%) had one or more abnormal tests. All patients with abnormal perimetry and/or fundus examination had also CST and/or VEP altered. It is apparent that CST and VEP reveal a significant proportion of abnormalities in the visual system that have not been revealed by routine neuroophthalmological examination.