Adaptations Proposed to Help Assess Eye Tracking in Rett Syndrome Patients, Study Reports

Researchers from the Maastricht University in the Netherlands have suggested a series of adaptations to help with the assessment of eye movements in patients with Rett syndrome.

Their study, “Challenges in evaluating the oculomotor function in individuals with Rett syndrome using electronystagmography,” was published in the European Journal of Paediatric Neurology.

Rett syndrome is a rare genetic disorder characterized by developmental and intellectual disabilities that affect mostly girls. Rett patients typically lose the ability to communicate through speech, but seem to be able to communicate using eye movements.

For this reason, in recent years, eye tracking technologies that can assist in communication between Rett patients and their caregivers and physicians have started to be implemented in the clinic.

However, assessing eye movements in Rett patients may not be straightforward, because there are many challenges that need to be addressed, including patients’ lack of attention.

In this research — which was the second stage of a two-part study based on the premise that girls with Rett syndrome communicate through eye movements — researchers set out to evaluate the occurrence of artifacts associated with eye movement and propose alternative strategies to overcome them.

The study enrolled 17 girls and young women diagnosed with Rett syndrome and 16 typically developing individuals used as controls, all of whom underwent electronystagmography (ENG). This technique works by recording involuntary eye movements to determine how well two nerves in the brain — the acoustic and occulomotor — are functioning.

Participants sat on a chair in a semi-darkened room with electrodes placed around their eyes. For the Rett syndrome group, “photographs of individual family members and images of animals were projected onto the wall in front of them,” according to the researchers.

For the control group, cartoon characters and images of animals were projected. “Each participant was required to follow the movements of the digital images with their eyes, without moving their head,” they said.

Eye movements were registered by the electrodes and transmitted to the computer via a transducer worn around each participant’s neck. All participants performed at least one trial in several eye tracking tests, including saccadic eye movement (where the eyes move in the same direction as a moving image), smooth pursuit eye movement (where the eyes closely follow a moving object), involuntary movement of the eyes, and torsion swing test (where individuals have to turn their head to look at an image).

The main outcomes analyzed were quality of attention — measured in percentage of looking time — and quality of signals — measured in drift — during tests of eye movement in Rett patients.

The biggest challenges that occurred during examinations were linked to the patients’ lack of attention and low quality of electrode signals. Poor attention was demonstrated by a low percentage of time looking at the wall. The low quality of electrode signals was illustrated by a high degree of drift.

In all tests, apart from the torsion swing, attention and signal quality were significantly decreased in the Rett patients’ group compared with the control group.

“The challenges in testing confirm that regular oculomotor examination should be adjusted to meet the needs of individuals with [Rett syndrome],” the researchers wrote.

“Suggested adaptations include reducing the number of electrodes, changing the picture stimuli and bringing them closer, performing [manual] observational assessments rather than [automated] ENG, and using virtual reality goggles,” they concluded.