Objective: This pilot study examined the analytical and clinical validation of OMT measurement via the iTremor ONE device in PwPD.

Background: Ocular microtremor (OMT) is an involuntary fixational eye movement linked to brainstem activity. It has been shown to have a mean frequency range of 70 – 90 Hz in healthy adults. Previous research suggests OMT is reduced in neurological diseases such as in people with Parkinson’s Disease (PwPD), therefore, OMT represents a potential objective digital biomarker for diagnosing and monitoring neurological conditions. Historically, OMT has been measured invasively using lengthy protocols. The iTremor ONE device is a novel method for measuring OMT quickly, comfortably, and non-invasively.

Method: A total of 34 PwPD and 31 age matched controls participated in this study. Measures of motor function and OMT frequency (Hz) were assessed. For analytical validation, 22 PwPD completed a test re-test assessment of OMT frequency, with assessments one week apart. Interclass correlation coefficients (ICC) were used to assess test-retest reliability. For clinical validation, ROC curve and AUC was used to assess diagnostic ability of OMT in PwPD (n=22) vs. controls. 24 PwPD were also tested 12 hours ‘OFF’ their dopaminergic medication. Correlations were explored between OMT frequency and the clinical rating scales.

Results: The iTremor ONE reliably measured OMT in PwPD. OMT frequency (Hz) had excellent agreement in test-retest reliability for the right, left and both eyes (ICC >0.9). OMT had excellent (AUC >0.7) discriminative ability in differentiating between PwPD and controls. No substantial change was seen in OMT frequency or MDS-UPDRS in response to medication in PwPD.

Conclusion: The iTremor One Device reliably measured OMT in PwPD and OMT was associated with selective aspects of PD disease severity. The present study found no difference in OMT frequency in response to medication. Future work should explore the relationship between OMT, and other neurotransmitter systems involved in PD e.g. acetylcholine This is the first study of its kind to investigate OMT as a marker/monitor for PD with non-invasive technology that can be used within the clinic, laboratory, and home settings. Identifying a reliable measure for OMT as a potential biomarker for PD, could support clinicians in their assessments and enable better provision of care to patients allowing improved disease monitoring.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/digital-measurement-of-ocular-microtremor-in-parkinsons-disease-analytical-and-clinical-validation/