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Abnormalities in horizontal eye movements detected with video oculography (VOG) may support the early diagnosis of atypical forms of Alzheimer’s disease (AD), according to a French study that adds to growing evidence supporting ocular biomarkers in the screening of neurodegenerative disease.

The findings were presented during the French Language Neurology Days 2026. Experts also discussed the value of VOG in atypical Parkinsonian syndromes and the potential role of pupil dilation measurements in early AD.

“Specific protocols still need to be established before its use can be routinely expanded to the early detection of neurodegenerative diseases,” said Lejla Koric, MD, neurologist at Hôpital de la Timone, Assistance Publique - Hôpitaux de Marseille, Marseille, France.

Assessment of the ocular motor system may aid in the diagnosis and monitoring of neurodegenerative diseases such as AD, along with conditions including multiple sclerosis, autoimmune myasthenia, progressive supranuclear palsy (PSP), and certain language and learning disorders such as dyslexia, autism, and attention-deficit hyperactivity disorder.

In neurodegenerative diseases, assessment of eye movements using VOG is already used to screen for atypical Parkinsonian syndromes such as PSP, which is characterized by the slowing of voluntary vertical saccades. These vertical eye movements help reposition the gaze while tracking a target.

In corticobasal syndrome, a progressive atypical Parkinsonian disorder, early findings often include asymmetric prolongation of saccade latency, which is often characterized by a significant delay in initiating eye movements to follow a target. 

In cerebellar-type multiple system atrophy (MSA-C), eye movement abnormalities are prominent early features, with nystagmus often described as “eye tremors” and dysmetric saccades, a type of eye movement disorder (oculomotor dysmetria) characterized by saccades that are too wide or narrow. While irregular pursuit is observed in both MSA-C and Parkinson’s disease, it is typically more pronounced and rapidly progressive in MSA-C, Koric noted.

Koric described the case of a 62-year-old patient who presented with behavioral changes. Family members reported apathy, while the patient reported “mild unsteadiness” when walking. Cognitive testing was normal, although neurologic examination showed a “slight decrease in postural reflexes without Parkinsonian syndrome.”

VOG recordings showed a slowing of voluntary vertical saccades, while horizontal saccades were “generally preserved.” The patient also experienced a 100% error rate during antisaccade testing on both sides of the eyes. In this task, patients were instructed to look in the opposite direction of the moving target.

“These findings reflect dysfunction in the brainstem regions and prefrontal lesions,” Koric said. Slowing of vertical saccades supported the diagnosis of PSP.

In individuals with AD, studies have shown that distinct oculomotor abnormalities, such as prolonged horizontal saccade latency, irregular tracking, and increased antisaccade errors, are key indicators of underlying cortical damage often detectable via VOG, although these abnormalities are not disease-specific.

According to Koric, VOG may still prove useful in the early detection of posterior cortical atrophy, an atypical form of AD that initially presents with higher-order visual dysfunction, such as impaired spatial awareness and blurred vision, appearing well before the onset of symptoms of memory loss.

To evaluate the role of VOG in phenotyping patients with AD, Koric and colleagues studied approximately 30 patients in the early stages of the disease who presented either with visual impairment linked to posterior cortical atrophy or with amnestic syndrome. Researchers compared oculomotor parameters with those seen in healthy individuals.

The results showed longer latencies for horizontal saccades and a higher number of antisaccade errors among patients with posterior cortical atrophy.

Errors involving left antisaccades demonstrated 96% specificity compared with healthy individuals, suggesting that these abnormalities may serve as a promising ocular biomarker for early detection of PSP.

Other studies have also highlighted pupil dilation during cognitive tasks as a preclinical biomarker for AD. One study showed greater pupil dilation during cognitive effort among patients with mild cognitive impairment than among healthy individuals, suggesting a compensatory mechanism.

“As the cognitive load increased, pupil dilation also increased. Compared with healthy individuals, patients showed greater dilation, suggesting increased cognitive effort,” Koric said.

According to Koric, assessment of eye movements “improves the sensitivity of clinical examinations” in certain situations and “opens up new possibilities for the use of ocular biomarkers” in screening for neurodegenerative diseases.

She noted that further research is still needed, particularly to standardize protocols.

This story was translated from Medscape’s French edition.