Set Up Eyetracker with Subjects
You incorporated Eyelink MATLAB code into your experiment, you have a participant with great eyes that are ready to be tracked. Now what? Below you'll find information that helps you set up the tracker specifically for the participant.
Step 1: To change from recording monocular to binocular or vice versa, click "Set Options" from Eyelink taskbar and the top of the screen should look like it does below. Click "Select Config..."
Step 2: Then choose one of the first two options displayed below (MTABLER if you want to record from one eye and BTABLER if you want to record from both.)
Step 3: The chin and forehead rest do not need to be adjusted for each participant. First adjust the seat height below, and then if necessary adjust the chin and forehead rests. Please note that the eyes should be level with the top quarter of the display monitor.
When the participant is comfortably seated with their chin and forehead resting in the appropriately places, look at the camera set-up. The position of the forehead rest should be just above the eyebrow (see left picture below). Adjust the height of the participant's chair according to the pictures below.
Step 4: If tracking both eyes, click "Both" at the bottom of the Camera Setup screen. Place the cursor on the pupil and click for each eye. You will notice, the red circle and green square (pictured above) will center around the point you clicked. Turn the lens so that the eye is in good focus (see below).
Step 5: Ask the participant to look at the display screen and click the "Auto Threshold" button near the top left of the screen. The pupil and CR numbers for that eye will change. These numbers are located below the zoomed view of the eye. Now, click the zoomed view of the eye that is not in the purple box. Once you click, this eye will now be in the purple box. Repeat the steps above: ask the participant to look at the screen and click "Auto Threshold".
Make sure the pupil and CR levels are optimal. Most of the pupil should be covered with a blue circle and there should not be any "shadows". If the zoomed views of your participant's eyes do not look like the center picture below, adjust the pupil level using the arrows in the top left corner of the screen. Remember, the levels are being adjusted for the eye that has a zoomed view in a purple box.
Step 6: The smaller teal dot will determine if the corneal reflection is good. If your participant's zoomed views do not look like the center picture below, use the arrows to adjust the CR levels.
Step 7: When calibration, validation and drift correction are running, follow the steps below. The EyelinkDoTrackerSetup function should be used in your code.
Pressing ESC on the Host PC keyboard on the calibration or validation screens does not accept the calibration and validation fixation points. Instead, pressing ESC will erase them!
Start calibration by either clicking "Calibrate" on the tracker page or pressing C on the Host PC keyboard. During calibration if you or the participant is unsatisfied with a point, you can press BACKSPACE to erase the last point. You can calibrate as many times as you'd like, but it will only save the last calibration. If you want to restart, press ESC on the keyboard. When you are done calibrating, click "Accept Fixation" on the tracker page or press ENTER on the keyboard. You can also press V on the keyboard, this will accept the calibration points and go directly to the validation screen. The buttons and keys work in a similar way for validation: start validation by either clicking "Validate" on the tracker page or pressing V on the Host PC keyboard. Click "Accept Fixation" on the tracker page or press ENTER on the keyboard when you are satisfied with the participant's fixation.