Oculometrics
The Science Behind Eye Movement Analysis
Eye movements reflect the health of multiple brain regions. Oculometrics captures these functional patterns to identify functional biomarkers for neurological and ophthalmological conditions before traditional imaging detects structural changes.
In this section, discover how oculometrics detects functional changes in specific conditions. More articles coming soon.
Bulbitech Research & Collaborations
PEER-REVIEWED
Eye-tracking-derived foveal biomarkers and functional alterations in dry AMD: findings from a controlled clinical study
Helland-Hansen et al.
Clinical Ophthalmology (2025)
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Purpose
Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly, and early detection is essential for timely intervention and slowing disease progression. This study validated novel foveal function tests using the Bulbicam (BCAM) device for differentiating early and intermediate dry AMD from healthy controls (HCs) and to identify functional variables that may serve as candidate biomarkers.
Methods
In a controlled clinical study, 17 patients with early and intermediate dry AMD and 17 age-matched HCs were assessed using the proprietary Bulbitech “ACOLAPT” (Acuity, Contrast, Light Adaptation) test. Each eye was classified as either the “Worst eye” or “Best eye” for AMD patients based on predefined clinical criteria. Foveal function metrics were derived from the five main variables: Pursuit acuity (PuAc), Pursuit contrast sensitivity (PuCS), Strobe Pursuit Contrast Sensitivity(StCS), (PuCS − StCS) / PuCS (ΔCS), and Variable Strobe Pursuit Object Detection(VaSt). Test validity, reliability, repeatability, and stability were assessed. Validation of ACOLAPT included Analysis of Variance (ANOVA) and Receiver Operating Characteristic (ROC) analyses to assess discriminative capacity, intraclass correlation coefficients (ICC) and Bland-Altman plots with Agreement Index (AI) to evaluate reliability and Stability Index (SI) for estimation of stability.
Results
All five BCAM tests showed significant differences between AMD patients and HCs in the worst eye (p ≤ 0.05). PuAc and PuCS showed good reliability (ICC ≥ 0.77), good repeatability (AI ≥ 0.75), and excellent stability (SI ≥ 0.59). The novel StCS test demonstrated excellent reliability (ICC = 0.96), excellent repeatability (AI = 0.88), and excellent stability (SI = 0.58). Despite good ICC values, VaSt and ΔCS had lower repeatability (AI ≤ 0.25), highlighting the importance of AI and SI metrics.
Conclusion
PuAc, PuCS, and StCS fulfilled the predefined criteria for reliability, repeatability, and stability, supporting their use as candidate biomarkers at both population and individual patient levels. VaSt also met the predefined biomarker criteria through preserved cross-session stability despite lower single-trial agreement. ACOLAPT’s ability to assess multiple aspects of foveal function, along with enhanced stability and repeatability metrics, suggests that it could be valuable in clinical settings for early AMD detection and monitoring.
PEER-REVIEWED
Dynamic Pupillary Responses in Age-Related Macular Degeneration: A Controlled Clinical Study Using High-Frequency Video-Oculography
Helland-Hansen et al.
International Journal of Retina and Vitreous (2026)
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Purpose
To investigate whether dynamic pupillary responses differ between patients with age-related macular degeneration (AMD) and healthy controls (HC), and to evaluate their potential as functional biomarkers using high-frequency, VR-based video-oculography.
MethodsA controlled clinical study included 17 AMD patients and 17 age-matched HCs; four AMD participants were excluded for low recording quality. Dynamic pupillary responses were recorded with the BulbiCam video-oculography system (400 Hz), which presented independent monocular light stimuli through multiple permutations of bright (300 cd/m²) and dark (5 cd/m²) conditions. Measured variables included pupil diameter, latency, peak velocity, and pupil diameter–time integral (PDTI). Each eye was tested separately, and repeated sessions were analysed for reliability (intraclass correlation coefficient, ICC), repeatability (agreement index, AI), and stability (stability index, SI). Group differences were assessed using analysis of variance (ANOVA) and receiver operating characteristic (ROC) analysis.
ResultsAMD eyes showed larger steady-state pupil diameter and higher PDTI than controls (p < 0.05). First peak velocity was reduced in the worst eye only, while latencies were unchanged. PDTI and diameter demonstrated high reliability and stability across repetitions, and ROC analysis confirmed effective group discrimination.
ConclusionHigh-frequency VR pupillometry detected reproducible functional alterations in AMD, consistent with impaired macular photoreceptor input but preserved reflex transmission. PDTI and diameter serve as diagnostic (population-level) and monitoring (patient-level) biomarkers, offering a non-invasive and objective method for AMD detection and follow-up in clinical and research settings.
PEER-REVIEWED
Eye-tracking biomarkers for glaucoma based on saccadic reaction time: a controlled clinical study
Sverstad et al.
Frontiers in Ophthalmology (2025)
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Purpose
Evaluate the validity and reliability of saccadic reaction time (SRT)-based variables obtained using the novel eye-tracking device Bulbicam (BCAM) in differentiating early-to-moderate glaucoma (GLA) from healthy controls (HCs) and to identify potential biomarkers for GLA.
Methods
A controlled clinical study was conducted, involving 18 GLA-patients, and 18 age-matched HCs. Participants underwent BCAM’s visual field (VF) test, which measures SRT at 58 symmetrically arranged locations with 6° spacing. Variables were analysed for group differences, within- and between-patient repeatability, and stability. To evaluate their potential as biomarkers, VF locations were aggregated into clusters, quadrants, hemifields, and whole VF analyses.
Results
Significant SRT differences (p ≤ 0.05) were observed between GLA and HC in 44 of 58 locations in the worst eye and 42 of 58 in the best eye. Eight out of ten clusters met the criteria for BCAM biomarkers having significant group differences, sufficient within- and between-patient repeatability, and adequate stability. All quadrants demonstrated excellent stability and repeatability thereby qualifying as biomarkers. Hemifield SRTs were reliable, however, the absolute difference between hemifields showed poor within-participant repeatability. The mean and standard deviation of SRT for the whole VF were identified as significant biomarkers with excellent stability.
Conclusions
The majority of SRT variables are capable of differentiate glaucomatous eyes from HC while maintaining sufficient reliability and stability for clinical application. 19 of 22 BCAM VF test variables were found to be potential GLA-biomarkers.
PEER-REVIEWED
Repeatability, reliability, and stability of eye movement measurements in Parkinson’s disease, cerebellar ataxia, and healthy adults
Dalbro et al.
Frontiers in Neurology (2025)
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Introduction
Eye movements have been proposed as biomarkers to track disease progression and treatment effects in neurological diseases. Before such variables are used in the clinic or in drug trials, properties such as measurement error must be documented. In this study, we assessed repeatability, reliability, and stability of fixation, smooth pursuit, and saccade measurements in patients with Parkinson’s disease, cerebellar ataxia, and healthy adults.
Methods
Fixation, smooth pursuit, and saccade metrics were measured in 16 patients with Parkinson’s disease, 16 patients with ataxia, and 25 healthy adults with an eye tracker (BulbiCam). The same operator repeated the measurements six times over 2 days in the patient group and two times the same day in the healthy adults. Reliability, repeatability, and stability were assessed with the intraclass correlation coefficient (ICC), Bland–Altman plots with the Agreement Index, and the Stability Index, respectively.
Results
Mean pupil size in the fixation test and latency, accuracy and peak velocity in the pro-saccade test were found reliable, repeatable, and stable. Mean and max fixation in the fixation test were found reliable and stable. Smooth pursuit measurements were found repeatable within patients and stable, but not reliable.
Conclusion
The saccade and pupil variables may be used both on a population level and for individual patient follow-up. Mean and max fixation duration may be used on the population level but used in the clinical evaluation on individual patients they need to be repeated.
PEER-REVIEWED
Pupil-light reflex in early-stage Parkinson's disease
Dalbro et al.
Journal of Parkinson’s Disease (2026)
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We examined pupil-light reflex in 25 drug-naïve patients with newly diagnosed Parkinson's disease and compared them to 29 healthy controls. We also evaluated effects of symptomatic treatment and correlations with clinical scores. Besides a smaller pupil diameter at maximum constriction, no pupil parameter robustly distinguished patients from controls. Following initiation of symptomatic therapy, baseline pupil diameter and constriction amplitude increased, whereas peak constriction velocity remained unchanged and correlated with patient-reported autonomic symptoms. These findings suggest peak constriction velocity may reflect autonomic dysfunction less influenced by medication. Further studies should clarify the pupil-light reflex's clinical utility in Parkinson's disease.
Plain Language Summary Title
Pupil response to light in newly diagnosed Parkinson's patients
Plain Language Summary
We tested pupil responses to light in 25 newly diagnosed, unmedicated Parkinson's patients and 29 healthy people, then retested patients after starting Parkinson's treatment. Pupil responses did not clearly detect early Parkinson's. After treatment, resting pupil size increased, but peak constriction velocity did not change and was linked to patients' autonomic symptoms. Peak constriction velocity may be a medication-resistant marker of autonomic dysfunction and deserves study in larger trials.
Independent / External Research Using BulbiCAM
PEER-REVIEWED
Diagnostics and rehabilitation of post-stroke visual field loss using innovative visual field evaluation. The impact of losing driving privileges (DRIVE-study): Protocol for a randomized controlled trial
Rosenvinge et al.
Scientific Reports (2026)
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Introduction
The overall aim is to explore the impact of losing driving privileges and to estimate the effect of compensatory vision rehabilitation in Norwegian stroke survivors whose driver's licenses have been revoked due to VFL. Specifically, to evaluate the effect of vision rehabilitation on perceived and measured functional vision, and secondarily explore markers for perceived functional vision and functional visual field that may predict an effect of vision rehabilitation.
Methods
This study is an open, randomized controlled trial (RCT) with delayed-start design. Stroke survivors aged 20-85 years (N = 52) will be recruited from a vision rehabilitation clinic in Norway and randomized into two arms: A) immediate start of eight-week home-based vision rehabilitation intervention and B) delayed start (eight weeks) of the same eight-week vision rehabilitation intervention. A quantitative and qualitative approach will be applied to assess changes in functional vision after eight weeks of vision rehabilitation, and at twelve weeks post-intervention in both groups. The quantitative analysis includes descriptive statistics, plots and inferential statistics of effects. In addition, ten participants will be recruited for qualitative individual interviews before and after the eight-week intervention to explore experiences of living with VFL and participating in the intervention. For the qualitative analysis, we will apply thematic analysis.
Conclusions
The study is designed as an RCT that will give important insight into the effectiveness of vision rehabilitation for visual field loss after stroke on functional vision measured by a novel VR-vision test.
PEER-REVIEWED
Artificial intelligence-driven virtual reality eye-tracking for the objective measurement of MRD1 and MRD2 in blepharoptosis
Savant et al.
Contemporary Clinical Trials Communication (2026)
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Accurate measurement of eyelid position is essential for diagnosis and surgical planning in blepharoptosis, but traditional manual assessment using pen torch and ruler is subject to inter-observer variability and lack of standardisation. We evaluated an artificial intelligence-enabled virtual reality eye-tracking system to provide an objective alternative to current manual methods. In 101 patients with suspected blepharoptosis, the BulbiCAM device employed high-speed infrared video-oculography with convolutional neural network algorithms to automatically detect the pupil centre, corneal glint, and eyelid margins. When benchmarked against standard clinical assessment to establish validity, automated measurements showed high agreement, with mean differences of + 0.29 mm for upper eyelid position and + 0.01 mm for lower eyelid position. Critically, the device demonstrated high precision, with test-retest repeatability in 36 patients showing mean differences of − 0.03 mm and + 0.27 mm between visits. Successful acquisition was achieved in all participants with a median of one attempt, and 98% reported the device as comfortable and easy to use. This study demonstrates that AI-enabled VR eye-tracking matches the clinical accuracy of current standards while offering the repeatability and objectivity required to overcome the limitations of manual assessment.
PEER-REVIEWED
Technical validation of a virtual reality-based eye tracker for neuro-ophthalmic assessment: a reliability and reproducibility study
Karaer et al.
Scientific Reports (2026)
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Virtual Reality (VR) eye trackers provide portable and objective tools for neuro-ophthalmic testing. This study aimed to assess the reliability and reproducibility of an emerging VR-based eye tracker (BulbiCAM) in healthy participants and compare its utility to an existing wearable eye-tracking system (PupilLabs Neon), thereby laying the groundwork for the future studies of clinical feasibility. Thirty-nine healthy participants underwent BulbiCAM testing across two visits, with inter-visit reproducibility evaluated using intra-class correlation coefficients. Pupillary light reflex assessments were conducted with both devices, allowing paired comparisons. Participant feedback demonstrated high acceptability, with 89% reporting the test as comfortable and 81.5% experiencing no eye strain or fatigue. BulbiCAM showed high reproducibility for pupil and pursuit tests (ICC = 0.76–0.88), though saccade reproducibility was lower (ICC = 0.46–0.62) which indicates limited reliability for saccade metrics. Key pupillometric parameters showed strong agreement between devices, with minimal bias observed in baseline diameter (-0.48 mm), peak constriction (-0.56 mm), constriction velocity (0.22 mm/s), and duration (-0.052 s). These findings support the potential clinical feasibility and reliability of BulbiCAM for both research and patient testing, offering a promising alternative for objective neuro-ophthalmic assessment.
Pupil Dynamics
Professor Michael Strupp presents a lecture on Pupil Dynamics
Michael Strupp, MD, FRCP, FAAN, FANA, FEAN, is Professor of Neurology and Clinical Neurophysiology at LMU University Hospital Munich.
The lecture was delivered to invited guests as part of Bulbitech's ongoing efforts to advance objective neurological and ophthalmological assessment through eye movement analysis and video oculography.