Subclinical visual involvement in multiple sclerosis: a study by MRI, VEPs, frequency-doubling perimetry, standard...

To evaluate the effectiveness of visual evoked potentials (VEPs), frequency-doubling perimetry (FDP), standard achromatic perimetry (SAP), contrast sensitivity (CS) test, and magnetic resonance imaging (MRI), isolated or in combination, in detecting subclinical impairment of visual function in multiple sclerosis (MS).

Twenty-two eyes of 11 patients affected by clinically definite MS, without a history of optic neuritis and asymptomatic for visual disturbances, underwent full ophthalmic examination and, in addition, VEPs, FDP, SAP, CS, and MRI. Abnormal results were taken to be as follows: for VEPs, a P100 latency >115 ms; for FDP, abnormal mean deviation (MD) or pattern SD (PSD); for SAP, abnormal MD or PSD; for CS, abnormal CS at one spatial frequency, at least; and for MRI, evidence of at least one demyelinating plaque along the visual pathway.

VEPs showed abnormal results in 12 eyes (54.4%), FDP in 11 (50%), SAP in 14 (63.6%), CS in 17 (77.1%), and MRI in 16 (72.7%). In only two (9.1%) eyes of the same patient was no abnormality found. No single test detected all the abnormal eyes. Four (18.2%) eyes had pure optic nerve involvement and the remaining 16 (72.7%) had both pre- and postchiasmal involvement.

In patients affected by clinically definite MS without history of optic neuritis and no visual symptoms, there is a large prevalence of visual pathway involvement that can be diagnosed only by performing multiple tests. The comparison of the tests is also useful to detect the presence of multiple lesions in the same patient.