Eye Tracking

Last modified by Iris Spruit on 2024/09/06 12:59

Contents

🚧 This page is under construction 🚧

Introduction

With eye tracking one can obtain information about a person's gaze (where someone is looking) and pupil size.

Availability, Support and Use-case

At the FSW Leiden mainly Tobii and EyeLink eye trackers are used. At the LIBC MRI Scanner an EyeLink eye tracker can be used.

Getting Started with Eye Tracking

Below you will find some useful further reading when starting out with eye tracking.

Eye tracker models/brands

At SSH Leiden there are different eye tracker models from Tobii and EyeLink.

Tobii

How do eye trackers work

Software

Pupil data

  • Tobii Webinar: Power of the pupil
  • Pupil data analysis with the PhysioData Toolbox
  • EyeLink pupil size is reported in an arbitrary pixel unit, but can be converted to mm, see video (artificial eye required) and instructions (using printed out dot). Note that when you want to obtain pupil data with EyeLink, a chinrest must be used.

Procedure

The procedure for using eye tracker depends greatly on the eye tracker model and the task presentation software that is used. 

Tobii

Eye tracker setup

When using a Tobii Pro remote eye tracker (Fusion, Spark, X3-120, X2-60, Nano) the eye tracker needs to be configured after connecting it to a computer. This configuration needs to be performed each time the eye tracker is connected to another computer. See the Eye Tracker Manager for instructions how to configure the eye tracker. Only after this setup, the eye tracker can be used with the desired task presenting software. When the eye tracker stays connected to the same PC, this configuration only needs to be done once.

Calibrating an eye tracker

Tips & Tricks

  • Reporting guideline eye tracking: Follow the Minimal reporting guideline for research involving eye tracking (2023 edition) when publishing a study that involves eye tracking. It is highly advised to report data quality. Data quality can be reported in terms of accuracy and precision (see also Best practices in eye tracking research and Tobii article about accuracy and precision). The percentage of valid gaze samples can also be reported. Make sure that you know how your eye tracking data collection software saves this information, or how this information can be obtained.
  • Good calibration: A good calibration of the eye tracker is important when you want to obtain high quality data. Make sure to familiarize yourself with the calibration procedure, and adjust the calibration according to the participant (e.g. when calibrating the eye tracker with children, less calibration points and/or video's can be used for the calibration.
  • Light conditions: Most eye trackers use near-infrared light to obtain information about reflections of this light on the eye and then use this information to be able to track the eye. To obtain the best quality of data it is highly advised to not have direct light shining in the eye tracker or in the participant's eyes. Other than that, it is recommended that the space in which eye tracking is done is not very bright or very dark.
  • Mapping screen-based eye trackers to screen: The Tobii screen-based eye trackers (Fusion, Spark, Nano, X3-120, X2-60) need to be mapped to the screen, which is done with the Tobii Pro Eye Tracker Manager (see Tobii Pro Eye Tracker Manager for instructions).