High-resolution, ultrafast, wide-field retinal eye-tracking for enhanced quantification of fixational and saccadic motion

Abstract

We introduce a novel, noninvasive retinal eye-tracking system capable of detecting eye displacements with an angular resolution of 0.039 arcmin and a maximum velocity of 300°/s across an 8°span. Our system is designed based on a confocal retinal imaging module similar to a scanning laser ophthalmoscope. It utilizes a 2D MEMS scanner ensuring high image frame acquisition frequencies up to 1.24 kHz. In contrast with leading eye-tracking technology, we measure the eye displacements via the collection of the observed spatial excursions for all the times corresponding a full acquisition cycle, thus obviating the need for both a baseline reference frame and absolute spatial calibration. Using this approach, we demonstrate the precise measurement of eye movements with magnitudes exceeding the spatial extent of a single frame, which is not possible using existing image-based retinal trackers. We describe our retinal tracker, tracking algorithms and assess the performance of our system by using programmed artificial eye movements. We also demonstrate the clinical capabilities of our system with in vivo subjects by detecting microsaccades with angular extents as small as 0.028°. The rich kinematic ocular data provided by our system with its exquisite degree of accuracy and extended dynamic range opens new and exciting avenues in retinal imaging and clinical neuroscience. Several subtle features of ocular motion such as saccadic dysfunction, fixation instability and abnormal smooth pursuit can be readily extracted and inferred from the measured retinal trajectories thus offering a promising tool for identifying biomarkers of neurodegenerative diseases associated with these ocular symptoms.

RETRACTED ARTICLE: Eye tracking: empirical foundations for a minimal reporting guideline

“…Retinal imaging systems also generally occlude forward viewing, impeding stimulus presentation. This may however change: Bartuzel et al (2020) describe a MEMS-based retinal imaging system that allows for presentation of stimuli while recording with a high sampling frequency (1240Hz). Even then, the measurement range (also "trackable range") tends to be smaller than with other eye trackers: Bartuzel et al (2020) report an 16 • range (8 • left, 8 • right), which we can compare to 20-40 • for the DPI and many video-based P-CR trackers, and 90 • or more for scleral coils.…”

Stimulus-induced drift inhibition revealed by retinal eye-tracking

“…The high accuracy of the FET with 0.039 arcmin, compared to the EyeLink with 9 arcmin 22,34 , suggests that saccade detection is reliable and that the results obtained are valid. We further conducted correlation analyses of all drift and microsaccade measures (Figs.…”

“…Eye movement data were acquired using the Freeze Eye Tracker (FET), described in detail in Bartuzel et al, (2020). Using the principle of the Confocal Scanning Laser Ophthalmoscope, the device acquires small (3x3deg), rectangular images of the retina, at 1240 frames per second.…”

“…To overcome the many obstacles of video-based eye trackers, we used un ltered data from the FreezEye Tracker (FET) developed at Nicolaus Copernicus University 22 . FET analyzes the displacements of the retina with a high sampling rate of 1240 Hz and an accuracy of 0.039 arcmin root mean squared error (RMSE); importantly, it is not pupil based.…”

Temporal phase evolution OCT for measurement of tissue deformation in the human retina in-vivo

“…In ophthalmic applications, the use of real time eye trackers, usually employing a scanning laser ophthalmoscope (SLO) integrated to an OCT system, has also greatly improved the stability of in-vivo measurements. Different tracking techniques have been implemented both in commercial and research OCT instruments, as seen in the literature [ 45 – 47 ]. Such technical improvements have fostered the use of OCT imaging for new applications.…”