In the field of ophthalmology, vision researchers use eye tracking to study oculomotor behavior, cognitive visual function and vision deficiencies. Quantifiable eye-movement analysis enables new diagnostic markers and identification of disease at a much earlier stage of progression. Current methodologies that rely on observation can be automated, reducing variability.
Eye tracking helps vision researchers to better understand eye movements and eye movement problems, and to develop means to prevent, diagnose and treat abnormalities or ocular disease in clinical situations. Eye tracking is used in both basic science research and clinical research.
Studies of true eye movements
Tobii eye trackers measure both the direction of gaze as well as the position of the eyes in space with high accuracy. This enables the calculation of head movements and, by extension, true eye movements within the orbit of the eye.
Various types of eye movements can be studied depending on which eye tracker model is used. A 300Hz eye tracker, for example, makes it possible to measure fast movements such as micro saccades.
Quantifying eye movement data facilitates comparison
Eye tracking allows researchers to quantify the dynamics of eye movement data. This is useful when studying eye movement data that contains valuable diagnostic information. The possibility of objectively quantifying such data means that it can be compared to published data and deviations related to a particular diagnosis or that impairments can be identified. Examples of quantifiable data include:
- Saccadic performance, such as latency, overshoot and undershoot
- Fixation stability, such as drift
- Smooth pursuit, such as asymmetries between eye movement and stimuli
- Alignment, such as strabismus (uncontrolled inward or outward eye movement) or amblyopia (lazy eye)
- Nystagmus (rapid eye movements), such as the slope of the slow phase and amplitude of the fast phase.
The figures below illustrate how differently a person with nystagmus reads (to the left) as compared to a normal subject (to the right).
Automation reduces variability and increases efficiency
Eye tracking enables eye movement studies in an objective and automated way that increases reliability and reduces variability. In vision research and testing involving children and nonverbal adults, as well as in clinical assessments of eye movements, automated processes can replace manual observation.
Standardized and automated processes made possible with eye tracking are more time and cost-efficient. The ability to quantify eye movement data makes comparison, follow-up and progression studies more effective. Clinical areas where eye tracking can improve existing methods for screening and diagnostics are:
- Alignment such as strabismus (crossed eyes) or amblyopia (lazy eye)
- Fixation stability, smooth pursuit and saccadic movements
- Visual field testing
- Pediatric vision testing
Non-invasiveness adds validity
Tobii’s remote eye trackers provide a non-invasive method to study eye movements and eye movement deficits. They do not require placing any equipment on the subject’s head, and they allow for a great deal of free head movement. The result is a natural and relaxed test situation, imperative in research that involves young children.
Preferential looking paradigms
A Tobii eye tracker registers eye and head movements, and is therefore the perfect tool for registering preferential looking in an objective and automatic way. Preferential looking as an input method can be used in studies of:
- Visual fields.
Tobii eye tracking solutions
The Tobii TX300 Eye Tracker is designed for studies that require a higher sampling rate; e.g. the need to study eye movements such as saccades, correction saccades, fixations, pupil size changes and blinks. Sophisticated technology allows head movements to be subtracted from gaze direction data, thus measuring real eye movements.
The Tobii TX300 combines 300 Hz sampling rate, very high precision and accuracy, robust tracking, and compensation for large head movements, thereby extending the possibilities for unobtrusive research of oculomotor functions, for instance in children.
The wide, high-resolution screen allows researchers to present naturalistic as well as eccentric stimuli and longer pursuit trajectories. The display closely fills a subject’s field of view and enables automated preferential looking paradigms.
A wide range of research software applications are compatible with the Tobii TX300, including Tobii Toolbox for MATLAB, E-Prime Extensions for Tobii and Tobii Studio eye tracking software. Researchers who want to develop their own applications can download the Tobii Software Development Kit at no cost.