Investigative Ophthalmology & Visual Science· 2026Q1
Deep Brain Stimulation: A Window Into the Neural Mechanisms of Latent Nystagmus
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- 2026year
Short summary
Deep brain stimulation (DBS) targeting Forel's field H2 in a Parkinson's patient significantly reduced latent nystagmus metrics, including slow-phase velocity and strabismus angle, suggesting a cortical bias mechanism.
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Key points
- Latent nystagmus, associated with disrupted visual cortex connections, was studied in a Parkinson's patient undergoing subthalamic nucleus DBS.
- DBS targeting Forel's field H2 modulated visuomotor circuits, including pathways upstream of V1 and cortical projections to ocular motor regions.
- DBS significantly improved nystagmus metrics: reduced slow-phase velocity, quick-phase amplitude, strabismus angle, and disconjugacy.
- Improvements were observed across viewing conditions, particularly when the non-amblyopic eye fixated, and for both near and far gaze.
AI-generated from the title and abstract; the full text is not read.
Abstract
Purpose: Latent nystagmus is a condition marked by a nasal-ward drift of the eye that reverses depending on the fixating eye. It is commonly associated with early-onset strabismus and amblyopia and is hypothesized to result from disrupted horizontal binocular connections in the primary visual cortex (V1), leading to impaired cortical integration. This deficit extends to extrastriate areas, middle temporal (MT) and medial superior temporal (MST) regions, which are critical for coordinating conjugate gaze and vergence eye movements. The resulting imbalance in cortical processing creates a nasal-ward bias in eye movements and contributes to underdeveloped vergence and latent nystagmus. Methods: We investigated a unique case of latent nystagmus in a patient with Parkinson's disease (PD) undergoing subthalamic nucleus deep brain stimulation (STN DBS). Although DBS addressed PD motor symptoms, the electrode placement also enabled modulation of visuomotor circuits implicated in latent nystagmus. Specifically, stimulation targeted Forel's field H2, influencing the lateral geniculate nucleus (upstream of V1), parietopontine pathway (visual cortex projections to ocular motor regions, emphasizing the role of cortical bias), and cerebellar projections via the zona incerta. Results: We assessed five key outcomes: reductions in slow-phase velocity and quick-phase amplitude, decreased strabismus angle, and reduced disconjugacy of quick and slow phases of nystagmus. DBS significantly improved nystagmus metrics across viewing conditions, particularly when the non-amblyopic eye was fixating, and effects were consistent in both near and far gaze. Conclusions: These findings support a mechanism in which modulation of cortical bias and its downstream influence on brainstem ocular motor regions contributes to the pathogenesis of latent nystagmus.
The authors' abstract, as published at the source. Investigative Ophthalmology & Visual Science, 2026 · DOI ↗
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Field: Neurology (Medicine)
NeurologyMedicine