Direct access to retinal coordinates and fine spatial and temporal resolution are clear advantages of the retinal tracking methods over widely used video-based eye trackers. Several approaches to the retinal eye tracking have been proposed so far, including frame-to-frame scanning laser ophthalmoscope (SLO) tracking, reference-frame based methods using sub-sampled frames or our MEMS-scanner-based tracker capable of measuring both fixational and saccadic eye movements. In this work we present a novel approach to the design of the retinal MEMS-based tracking system, taking advantage of two combined high-speed MEMS mirrors to form a Lissajous scanning pattern with adjustable density and framerate.
We present a novel platform for eye tracking showing high speed and accuracy in a wide range of realizable visual tasks. The optical setup consists of the scanning laser ophthalmoscope, the actual tracker (the FreezEye Tracker), and a visual projector for task presentation. The MEMS-based tracker scans the retina with a framerate of 1.24 kHz, providing high angular and temporal resolution. Advanced algorithms allow for precise reconstruction of the eye trajectory covering the range of movements from small microsaccades to high amplitude saccades. The high quality of the generated data provides an abundance of data potentially useful for diagnostic purposes.
Neurodegenerative diseases, such as multiple sclerosis (MS), negatively impact the aging global population. MS damage various parts of the central nervous system, leading to various eye-movement abnormalities. We have built a retinal FreezEye Tracker (FET) to measure a wide dynamic range of eye movements of up to 10 degrees with an ultrahigh temporal and spatial resolution during visual tasks, including fixations, experiments with saccades, and smooth pursuit. To compare, we performed the same experiments with pupil tracker EyeLink 1000. The amplitudes of detected saccades are similar in both devices, but FET provides high-resolution details on eye trajectory during fixation periods.
Constructing an image acquired by a non-uniform scanning pattern is a difficult task. The main challenges are:(1) resampling technique (2) discrepancy between demanded (dictated by control signal) and actually performed, empirical scanning path. Here, we show how to calibrate the scanning path of MEMS scanner using Galvanometric Scanner and to what extent the time of acquisition impacts the resulting image.
KEYWORDS: Optical coherence tomography, Raster graphics, Speckle pattern, Visualization, Rods, In vivo imaging, Cones, Speckle, Signal analysis, Near infrared
Recent OCT based investigations in humans and in experimental animals have shown that rods and cones outer segments elongate in response to light stimuli. In this manuscript we describe our efforts to implement phase-based “optoretinograms” (ORG) analysis framework to retinal images acquired with standard raster scanning FD-OCT system, that offers much lower phase stability compared to full field or line field OCT acquisition schemes. Our initial results, acquired in anesthetized mice in vivo, showcase successful extraction of phase-based ORG signal and its favorable comparison with intensity-based ORG signal extracted from the same data sets.
The eye motion is broadly considered as a valuable source of information in the fields related to psychology, neuroscience and neurology. Therefore, quantitative characterization of eye tracker data is an important task. Saccades are sigmoidal, ballistic movements that in particular deserve more attention due to their complex shape and natural diversity. We have developed the high accuracy model of saccades and microsaccades of mean absolute error equal to 0.0104 degree on average. We present the methodology for extraction of saccadic features using this model and show the potential of the method in biometric experiments.
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