Abstract
Purpose :
Eye trackers using images of anterior eye features and light reflections from cornea and lens, widely used in eye movement research, require subject-dependent calibration with complex eye models, and are prone to errors caused by the dynamics of pupil and lens. As a result, are not accurate nor precise enough to reliably examine eyeglobe micro-movements. The purpose of this study was to register eye movements during various visual psychophysical tests with high accuracy and high precision using a retinal-based eye tracker prototype device that operates with high resolution and high speed.
Methods :
Our retinal tracker device is based on an optical arrangement of a confocal scanning microscope optimized for retinal imaging. The accuracy and precision of the prototype were measured using an artificial eye and model trajectories given to the scanning system. Then, eye movement trajectories were recorded for 8 healthy subjects aged 25-45 during different visual tasks, including 15-second fixation, saccades up to 4 degrees, and smooth pursuit up to 30 deg/second. Additionally, pilot studies were performed on 4 volunteers, during which the trajectory of eye movements was recorded at 2-hour intervals for 24 hours.
Results :
The prototype retinal eye tracker enables maximum precision from 0.03 to 2.4 arcmins (for drift and saccades), with an accuracy 0.02 to 0.1 degs (for saccades 0.25 and 4 degs). The device's calibration is subject-independent. Various psychophysical experiments can be performed due to the use of a scanning beam invisible to the human eye and a synchronized LCD screen that allows to display of any visual tasks created with PsychoPy software. The registered eye trajectories are segmented into microsaccades and drifts, followed by mathematical description of the basic parameters of these components. These parameters not only show individual differences but change in time due subject-dependent diurnal variability.
Conclusions :
Our eye tracker can register eye movements during psychophysical tasks with accuracy and precision significantly exceeding that offered by commonly used corneal eye trackers. This allows following the evolution of characteristic eye trajectory patterns over time. Additionally, it is a safe and non-invasive device for the examined subject, what makes it beneficial for monitoring patients diagnosed with various diseases, including mental and neurodegenerative diseases.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.