Tracking eye movements to diagnose Parkinson’s disease

A group of clinicians at the Division of Neurology at the Karolinska Institute in Stockholm, dedicate their research to the study of Parkinson’s disease and associated early biomarkers. Karolinska Institute is renowned for its excellent research centers, including the Marianne Bernadotte research center – which collaborated and shared its expertise in eye tracking with the Division of Neurology for this study. At the heart of this story is a medical doctor in Neurology and Ph.D. Panagiota Tsitsi. During her doctorate studies, she explored the possibility of using eye tracking as a prospective diagnostic tool for Parkinson’s disease, and her quest yielded exciting results.

Visual, oculomotor, and cognitive alterations are some of the common non-motor symptoms in Parkinson’s disease. Vision problems (although not always attributed to Parkinson’s) are underreported by health practitioners but are quite disturbing for individuals with Parkinson’s. Notably, these problems can be characterized in detail with an eye tracker. Eye tracking offers an objective, noninvasive, and time-efficient examination of eye movements and cognitive functions. In two research studies, Dr. Tsitsi showcased how tracking eye movements and pupillary responses with Tobii Pro Spectrum during simple tasks can distinguish individuals with Parkinson’s from their healthy peers.

In the first study, the participants (Parkinson’s disease patients and their healthy peers) were asked to focus on the black dot on the screen while their gaze fixation and pupil reaction were recorded with Tobii Pro Spectrum.

For data recording and filtering, the researcher used Tobii Pro Lab software. The results showed that in the Parkinson’s disease group, fixations were interrupted more easily, and the pupils were smaller during stable luminance conditions when compared to the control group. The study suggests that Parkinson’s disease diagnosis at early stages could be aided by measuring fixation and pupil reaction.

In the second study, Dr. Tsitsi focused on reading as a potential diagnostic tool for Parkinson’s disease-related cognitive alterations. The study participants read a short text, during which their eye movements were recorded with Tobii Pro Spectrum. The results showed that individuals with Parkinson’s disease perform longer fixations while reading, contributing to slower reading time compared to healthy peers. The researchers argue that reading alterations in Parkinson’s disease are associated with declining cognition rather than oculomotor changes.

Dr. Tsitsi shares a couple of tips on how to set up an eye tracking experiment with elderly participants or those with Parkinson’s disease:

• Generally, a quiet room with the possibility to turn off the lights, a comfortable chair, and an eye tracker is all you need.

• Simple and clear instructions and short-lasting paradigms make the task easier and more efficient.

Dr. Tsitsi shares her experience in using Tobii Pro Spectrum and Tobii Pro Lab in her experiments with elderly participants:

Although eye tracking-based assessment is not part of a neurology clinic routine, Dr. Tsitsi envisions eye tracking integrated into the clinical practice as part of neuropsychological/cognitive assessment. Eye tracking could be used in a primary care setting for an objective cognitive assessment of patients. Further algorithm development will provide the possibility of accessing direct eye tracking test results; the assessment could even be performed by non-medical personnel since the equipment is surprisingly easy to use. This would make assessments more efficient and accessible to more people.