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TL;DR
Eye movements are controlled by circuits across the brainstem, cerebellum, basal ganglia, and cortex, so changes in how the eyes move can reflect changes in brain function. Published research has linked specific eye movement patterns with Parkinson’s disease, progressive supranuclear palsy, Alzheimer’s disease, traumatic brain injury, and cerebellar disorders. Five measurements currently carry much of the evidence: saccades, fixation stability, smooth pursuit, pupillometry, and vergence.
Reliable eye tracking depends on precise timing, accurate calibration, data quality checks, controlled stimuli, and strong privacy safeguards. IntelliXR® gives researchers, solution developers, and pharmaceutical teams one platform to capture, manage, and study eye and brain biomarkers.
The Growing Role of Eye Movement Biomarkers
Neurological disease continues to place a growing burden on patients, healthcare systems, and clinical research.
An estimated 7.4 million Americans aged 65 and older are living with Alzheimer's disease in 2026. The cost of caring for people with Alzheimer's and other dementias is estimated at $409 billion in 2026 and is projected to approach $1 trillion in today's dollars by mid-century.
Parkinson's disease is following a similar trajectory. A modelling study published in The BMJ projects that 25.2 million people could be living with Parkinson's worldwide by 2050, representing a 112% increase from 2021.
Traumatic brain injury adds another significant burden, with an estimated 69 million people sustaining a TBI worldwide each year.
Across these conditions, researchers face a common challenge. Neurological change can be difficult to detect early, monitor consistently between clinical visits, and measure objectively during clinical studies.
Eye movements provide another source of measurable neurological information.
Even a simple glance depends on coordinated activity across the brainstem, cerebellum, basal ganglia, and several areas of the cortex. When disease or injury affects these systems, changes can sometimes be observed in how the eyes move, respond, and maintain visual attention.
Why Eye Movements are Useful Research Measures
For a biomarker to be useful in research, it needs to be measurable, repeatable, and practical to collect.
Eye movement measurements offer several advantages:
- Non-invasive
Eye movements can be recorded without blood draws, radiation, or injected tracers. - Fast to capture
Many oculomotor tasks can be completed within minutes, making them practical for clinical studies and repeated assessments. - Objective
Eye tracking produces quantitative measurements such as latency in milliseconds, velocity in degrees per second, fixation duration, and pupil diameter. - Repeatable
The same task can be performed across multiple visits, allowing researchers to study changes over time.
Together, these characteristics make eye movement measures relevant for research into earlier detection, longitudinal monitoring, treatment response, and clinical trial endpoints.
Five Eye Movement Measures Being Studied Today
1 Saccades
Saccades are the rapid eye movements used to shift gaze from one point to another.
Researchers typically measure:
- How quickly a saccade begins
- How fast the eyes move
- How accurately they reach the intended target
In Parkinson’s disease, saccadic abnormalities are among the most consistently reported eye movement findings, with several changes detectable during early-stage disease.
Progressive supranuclear palsy produces particularly characteristic changes. Vertical saccades are selectively slowed, and research using a short saccade task in a head-mounted display has shown the ability to distinguish patients with progressive supranuclear palsy from those with Parkinson’s disease and healthy controls.
Saccades are also being studied in cognitive decline. A meta-analysis identified significant differences in saccade latency and antisaccade error rates in both Alzheimer’s disease and mild cognitive impairment.
In traumatic brain injury, a meta-analysis covering 181 case-control comparisons found a moderate and significant effect on saccade and smooth pursuit performance, with similar overall effects across mild and severe injury.
2 Fixation stability
Fixation refers to the ability to maintain gaze on a single point.
Although fixation appears stationary, the visual system continuously makes small adjustments. When normal control is disrupted, involuntary movements known as saccadic intrusions can become more prominent.
In progressive supranuclear palsy, changes in the direction of these small fixational movements were found to be the feature that most effectively distinguished patients from controls.
Gaze-holding abnormalities, including nystagmus, are also characteristic findings in cerebellar disorders.
A recent study involving patients with CANVAS, a form of cerebellar ataxia, identified gaze-holding deficits in 70% of patients.
3 Smooth pursuit
Smooth pursuit allows the eyes to continuously follow a moving object.
A normally functioning pursuit system keeps gaze closely aligned with a moving target while minimizing lag and positional error.
Following mild traumatic brain injury, smooth pursuit can show:
- Increased lag
- Reduced accuracy
- Greater positional error
Research also suggests that these differences may become more apparent when participants perform the task under cognitive load.
Reduced smooth pursuit performance has also been reported in Alzheimer’s disease and mild cognitive impairment alongside abnormalities in saccades and fixation.
4 Pupillometry
Pupillometry measures changes in pupil size and response.
The pupil responds rapidly to changes in light, with the response governed by both visual pathways and the autonomic nervous system.
An objectively measured difference between the responses of the two pupils to light can be a strong indicator of optic neuritis. Changes in pupil response have also been associated with autonomic dysfunction in Parkinson’s disease.
In a validation study involving patients with autonomic disorders, pupil abnormalities were identified in 52% of patients with neurodegenerative conditions.
5 Vergence
Vergence describes the coordinated inward or outward movement of both eyes when focusing at different distances.
Convergence insufficiency is among the most frequently reported binocular vision problems following mild traumatic brain injury, and vergence is one of the commonly assessed binocular measures in this population. Changes in convergence have also been reported in Parkinson’s disease alongside abnormalities in saccadic eye movements.
What Reliable Eye Tracking Data Requires
The scientific value of eye movement data depends heavily on how that data is captured. Several technical requirements are particularly important:
- Precise timing
Eye responses must be synchronized with the exact moment a stimulus is presented. For many oculomotor experiments, differences of only a few milliseconds can matter. - Accurate calibration
Raw gaze data becomes meaningful only when the system has been calibrated for the individual participant. - Data quality indicators
Confidence scores, tracking quality measurements, and head motion data help researchers identify unreliable samples or trials. - Controlled stimuli
Studies involving pupil response, visual fields, or other visual tasks require consistent and known stimulus conditions. - Privacy safeguards
Eye images can contain biometric information. Research systems therefore need appropriate controls for image capture, processing, storage, and participant privacy. - Consistency across study sites
Multi-site research requires consistent hardware, software, configurations, and protocols so that measurements collected at different locations remain comparable.
What the Evidence Supports Today
Eye movement biomarkers are promising, but the current evidence should be interpreted carefully.
Many findings still come from controlled research environments. Protocols differ between studies, measurement methods are not always standardized, and findings can vary across patient populations.
Eye movement measurements are therefore best considered alongside clinical assessment and other biomarkers rather than as standalone diagnostic tests.
The next stage of biomarker research depends not only on identifying promising signals, but also on capturing them consistently enough to validate findings across:
- Larger populations
- Multiple research sites
- Longitudinal studies
- Different disease stages
- Repeated assessments over time
Standardized data collection will be central to that process.
How IntelliXR® Supports Eye and Brain Biomarker Research
IntelliXR® is a platform for eye and brain biomarkers. It brings together a clinical-grade XR headset, SDK and API capabilities, and IntelliMDM for device fleet management, allowing research and product teams to manage the infrastructure required for eye tracking studies within one platform.
The platform supports the measurements discussed above.
Saccades
The SDK reports:
- Saccade onset
- Peak velocity
- Amplitude
These measurements can support prosaccade, antisaccade, and memory-guided saccade tasks.
Fixation stability
IntelliXR® can capture:
- Fixation onset
- Fixation duration
- Fixation position
- Saccadic events occurring during attempted fixation
Smooth pursuit
Researchers can present moving visual targets while collecting a continuous gaze stream for pursuit analysis.
Pupillometry
The platform reports pupil diameter independently for each eye in millimeters. Stimulus luminance can also be controlled through the SDK for light-response studies.
Vergence
Binocular tracking provides convergence measurements alongside stereoscopic stimulus presentation.
Visual field testing
Native support for the Open Perimetry Interface allows research teams to run standard perimetry algorithms directly from R.
Head-mounted perimetry of this type demonstrated a 0.94 correlation with the clinical gold standard in a 100-participant trial.
Supporting Consistent Research Data
Beyond individual eye movement measurements, IntelliXR® includes capabilities that help research teams collect data consistently across participants, sessions, and sites.
These include:
- Synchronized timing
Eye responses and corresponding stimuli share synchronized timestamps. - Calibration support
Calibration routines help establish accurate gaze measurements for individual participants. - Data quality controls
Per-sample confidence scores and head motion information can help researchers identify unreliable trials. - Privacy controls
Eye images can be cropped to the ocular surface, the iris can be blurred, and identifying metadata can be removed before data leaves the device. - Multi-site device management
IntelliMDM can be used to maintain consistent configurations and policies across deployed headsets.
The IntelliXR® stack currently supports more than 10,000 users across 2,000 clinics, providing an infrastructure that can support both initial studies and larger multi-site deployments.
For teams studying early indicators of disease, longitudinal neurological change, treatment response, or emerging biomarkers, the requirement remains the same: reliable signals collected under repeatable conditions.
“Researchers have known for a long time that the eyes carry signals from the brain. The harder problem has been capturing those signals the same way every time, across every site, with data that stands up to scientific and regulatory review. That is the problem IntelliXR® solves, so research teams can spend their time on discovery instead of setup.”
Gaurav MalikChief Commercial Officer, CitrusBitsExplore Eye and Brain Biomarker Research with IntelliXR®
For research, pharmaceutical, and product teams studying eye movements as measures of neurological function, IntelliXR® provides the tools to capture these signals within a consistent XR environment.
Book a demo to explore the IntelliXR® platform or review the Biomarker Capability Reference for technical details on supported measurements.
Frequently asked questions
What are eye movement biomarkers?
Eye movement biomarkers are measurable characteristics of eye behavior, including:
- Saccade speed
- Fixation stability
- Pupil response
- Smooth pursuit
- Vergence
Because these movements rely on multiple neurological systems, changes in their characteristics can provide information about changes in brain function.
Can eye tracking detect Parkinson’s disease?
Research has associated Parkinson’s disease with several changes in eye movement, including saccadic abnormalities that may appear during early-stage disease.
Eye tracking is currently used as a research measure and supporting source of evidence rather than as a standalone diagnostic test.
Which eye movements are most studied in Alzheimer’s disease?
Saccadic tasks, particularly antisaccade tasks, are among the most widely studied.
Research has identified changes in saccade timing and antisaccade error rates in both Alzheimer’s disease and mild cognitive impairment.
Is eye tracking used after concussion?
Yes.
Research following mild traumatic brain injury commonly examines:
- Smooth pursuit
- Saccades
- Convergence
These measures are frequently affected following injury.
How is eye tracking data kept private in research?
Common approaches include:
- Cropping images to the ocular surface
- Blurring the iris
- Removing identifying metadata
- Controlling data access
- Recording appropriate participant consent
IntelliXR® applies image and metadata safeguards according to the privacy mode selected for a study.
How does IntelliXR® support biomarker research?
IntelliXR® combines:
- A clinical-grade XR headset
- SDK and API capabilities
- IntelliMDM fleet management
- Eye tracking and biomarker data capture
- Timing and calibration controls
- Data quality indicators
- Privacy safeguards
The platform supports the capture of saccades, fixation, smooth pursuit, pupil response, vergence, and visual field data within a single research environment.
