Ocular Motor Dysfunction in Multiple Sclerosis

Ocular motor dysfunction in multiple sclerosis arises primarily from inflammatory demyelination within the brainstem, cerebellum and their connecting pathways, leading to a spectrum of eye-movement abnormalities. Common manifestations include internuclear ophthalmoplegia, where conjugate horizontal gaze is disrupted; nystagmus, involving involuntary oscillations of the eyes; saccadic dysmetria, characterised by over- or undershooting target shifts; and smooth-pursuit deficits, impairing the ability to track moving objects. These disturbances not only contribute to visual symptoms—such as oscillopsia and diplopia—but also serve as non-invasive biomarkers for subclinical lesion burden, disease progression and cognitive dysfunction. Advances in quantitative oculography, orthoptic examination and digital eye-tracking have enhanced detection sensitivity, enabling the measurement of gaze stability, saccadic metrics (latency, peak velocity, accuracy) and conjugacy indices. By linking specific eye-movement parameters to lesion localisation, disability scores and quality-of-life measures, researchers are refining diagnostic protocols and exploring ocular motor metrics as outcome measures in therapeutic trials.

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Research from all publishers

Recent cross-sectional work has demonstrated that high-degree heterophoria may be present in more than one-third of individuals with multiple sclerosis despite minimal clinical signs, suggesting that prism diopter measurements during orthoptic assessment can unmask subclinical involvement. A population-based cohort study using infrared oculography identified internuclear ophthalmoplegia in roughly one quarter of middle-aged patients, revealing associations with male sex, greater overall disability and cognitive impairment but not with disease duration or self-reported visual complaints. Meanwhile, preliminary findings from a tablet-based eye-tracking platform have shown that a small set of oculomotor parameters—extracted during fixation, saccadic and smooth-pursuit tasks—can explain up to 84% of the variance in clinical disability and cognitive performance measures, highlighting the potential for remote, cost-effective monitoring of disease severity and treatment response.

Ocular Motor Dysfunction in Multiple Sclerosis publication trend

The graph below shows the total number of articles in ocular motor dysfunction in multiple sclerosis across all publications each year (not limited to Nature Index journals).

Technical terms

Heterophoria: Latent misalignment of the visual axes revealed when binocular fusion is interrupted.

Saccade: A rapid, ballistic eye movement that shifts the line of sight between points of fixation.

Smooth pursuit: A continuous eye movement that maintains foveal contact with a moving target.

Internuclear ophthalmoplegia (INO): A disorder of horizontal gaze due to lesion of the medial longitudinal fasciculus, causing adduction weakness on one side and abducting nystagmus of the contralateral eye.

Nystagmus: Involuntary, rhythmic oscillations of the eyes, often indicative of brainstem or cerebellar involvement.

Oculography: A technique for recording and quantifying eye movements, employing infrared sensors or camera-based tracking systems.

References

1. Heterophoria in multiple sclerosis patients: a proof of principle cross-sectional study. Frontiers in Immunology (2024).
2. The prevalence of internuclear ophthalmoparesis in a population-based cohort of individuals with multiple sclerosis. Multiple Sclerosis and Related Disorders (2022).
3. Oculomotor analysis to assess brain health: preliminary findings from a longitudinal study of multiple sclerosis using novel tablet-based eye-tracking software. Frontiers in Neurology (2023).
4. Eye Movement Abnormalities in Multiple Sclerosis: Pathogenesis, Modeling, and Treatment. Frontiers in Neurology (2018).
5. A standardized protocol for quantification of saccadic eye movements: DEMoNS. PLOS ONE (2018).