If you use spectacles for reading, put them on.

We will test one eye at a time; close the other eye firmly.

Darken your room (complete darkness is not required).

Avoid lights shining directly on the screen or in your eyes.

Sit 40cm from monitor, face-on.

Your gaze should be comfortably on the mid-point of the screen.

Alter your seat or screen height, or tilt screen to achieve this.