Microsaccades as recorded by the tracking scanning laser ophthalmoscope are associated with disability in MS

Abstract

Purpose : To evaluate the tracking scanning laser ophthalmoscope as a potential novel clinical biomarker of disability progression in multiple sclerosis.

Methods : The tracking scanning laser ophthalmoscope (TSLO) was used to perform retinal imaging and eye-tracking for 16 patients with confirmed multiple sclerosis (MS) from the UCSF MS center. The TSLO system uses 840 nm light to raster scan the retina over a 5-degree field of view. Videos of the retina were recorded at a 30 Hz frame rate and image-based software methods were used to extract eye motion for patients with MS (ages 21-70), with an average Expanded Disability Status Score (EDSS) of 3.3. For each recording, the patient was instructed to fixate on the upper right hand corner of the imaging raster for three, 10-second scans per eye. In an offline motion analysis, each of the 300 frames recorded was broken up into 16 strips to track fixational eye motion at 480 Hz. Blinks and low light levels were excluded from analysis. A median-Gaussian smoothing of the data was performed in order to eliminate eye motion artifacts at 30 Hz caused by the reference frame. Fixational eye motion metrics including velocity, amplitude, direction, frequency, standard deviation of frequency, and number of microsaccades were analyzed for each patient.

Results : Each patient’s average fixational eye motion metrics were compared to their EDSS, which quantifies the extent of disability in MS. A multivariable linear regression, accounting for age as a possible confounding variable, revealed the number of microsaccades occurring within a 10-s interval increased with increasing EDSS score (p=0.016). Aside from the comparisons of motion metrics, five of the sixteen patients exhibited a clear micro-nystagmus throughout recordings, with amplitudes as small 8 arcminutes recorded.

Conclusions : In this cohort, the TSLO system was used to successfully measure and quantify the fixational eye motion of patients with MS and these were correlated to their degree of overall clinical disability. Additional patients will need to be recruited in order to determine the significance of TSLO for use as a prognostic and monitoring tool.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.