What Is an Eye Tracker? | How Gaze Detection Works

These devices use infrared light and cameras to track eye reflections and calculate gaze position, moving from specialized research labs into consumer electronics, assistive technology, and medical diagnostics. The term refers to the hardware or the complete system that records gaze direction, eye movement, pupil size, blink rate, and three-dimensional gaze data. Eye tracking is broadly defined as measuring either the point of gaze or eye movement relative to the head. Modern trackers are compact enough to appear in laptops, VR headsets, and automotive driver-monitoring systems.

How Does an Eye Tracker Work?

Most modern eye trackers direct infrared light toward the eye and measure the reflected image with a camera. By analyzing how light bounces off the cornea and pupil—corneal reflection—the system calculates where the eye is pointing. Other systems use dark pupil tracking, relying on contrast between the dark pupil and lighter iris under infrared light, combined with a three-dimensional eye model to estimate gaze. As Tobii’s documentation on how modern eye tracking works explains, this repeats dozens or hundreds of times per second, producing a continuous gaze data stream. The sampling rate (in hertz) determines how finely the system captures rapid eye movements—consumer models sample at 30-60 Hz, while research systems reach 1200 Hz, enough to track individual saccades and microsaccades. Calibration is critical; most systems ask the user to look at a series of mapping points, with some models offering one-point or automatic calibration for quick setup.

What Are Eye Trackers Used For?

Eye tracking serves several major purposes with different performance requirements. In research, it reveals how people process visual information, what captures attention first, and how cognitive load affects gaze patterns—informing advertising design to cockpit layout. As assistive technology, it lets people with limited mobility control a cursor and communicate using only eye movements. Medical professionals use it for concussion assessment, neurological evaluation, and diagnosing visual processing disorders. Human factors engineers rely on it for product usability, website layout, and driver attention testing. Consumer applications include Windows Hello authentication and gaming immersion. Each use case demands different specs—assistive communication needs reliable accuracy but not ultra-high speed, while saccade research requires 500+ Hz. Research-grade trackers typically ship with SDKs and analysis software for custom experiments and raw gaze data export.

Key Specs: What the Numbers Mean

Sampling rate tells how often the system captures gaze data each second—higher rates catch finer movements like saccades and microsaccades for reading and cognitive studies. Accuracy measures how close the reported gaze point is to your actual fixation, given in degrees of visual angle (e.g., 0.5° means up to half a degree off). Precision describes how tightly clustered measurements are across repeated readings—both numbers matter, and specs differ depending on whether testing used a head-supported or head-free setup.

Real-world performance depends on lighting, glasses or contact lenses, head position, and distance—most screen-based models work best at 50-70 cm from the user. Wearable models like Tobii Pro Glasses 3 compensate for head movement with multiple sensors. Calibration methods range from one-point to 5, 9, or 13-point for research-grade precision. When comparing options, our guide to the best eye tracker models available today breaks down trade-offs between consumer and research-grade systems.

FAQs

Do eye trackers work with glasses or contact lenses?

Most modern eye trackers handle glasses and contact lenses, though thick or heavily tinted lenses may reduce accuracy. Anti-reflective coatings can distort infrared reflection, and progressive lenses may introduce small errors. Testing with your specific eyewear before committing is recommended.

How accurate are consumer eye trackers compared to research models?

Consumer models like Tobii Eye Tracker 5 prioritize ease of use and authentication over raw precision. Research models like Tobii Pro Spectrum achieve sampling rates up to 1200 Hz and precision down to 0.01 degrees RMS, essential for investigating rapid eye movements in scientific studies.

Can an eye tracker diagnose medical conditions?

Eye tracking is used clinically for assessing concussions, neurological disorders, and visual processing impairments, but consumer-grade trackers are not certified medical devices. Diagnosis should always come from qualified professionals using validated medical equipment.