Objective: Patients with multiple sclerosis (MS), due to the diverse nature of the disease, have many types of eye movement disorders, particularly internuclear ophthalmoplegia (INO). The aim of the study was to evaluate the usefulness of a quantitative statistical saccade test analysis for identification of INO in MS patients.

Methods: Sixty MS patients and 50 volunteers underwent clinical bedside ocularmotor examination and electrooculographic evaluation in a tertiary referral university hospital. Simultaneous electro-oculography recordings of each eye separately were made. In the saccade test, the versional dysconjugacy index (VDI) for saccades velocity and the Z score analysis were applied.

Results: Clinical eye movements disorders were found in 32% of patients. In the MS patients saccades velocity was significantly lower compared with the control group. Based on the results of the control group, we established the cut off values for VDI (1.04) and corresponded Z score (4.46) as the criterion indicated the presence of INO signs in MS patients. We confirmed clinical evidence of different degrees of INO in 15% of patients, and found subclinical INO signs in 20% of patients.

Conclusions: The EOG registration is a sensitive electrophysiological method for detecting subtle deficits of ocular motility. Saccade test analysis with calculation of the VDI and the Z-test score is a valuable method for identifying subclinical INO signs in MS patients.