Table 2. Visual discomfort questionnaire (modified from Hoffman et al, 2008).

Block questions (all rated on a 10-point scale) (1)How uncomfortable is this stimulus? (1: no discomfort, 10: aversive, like staring at a bright light) (2)Do your eyes feel dry? (3)How does your head feel? (4)How do your eyes feel? (5)Do you experience any distortion in the images? (1: no distortion, 10: like looking in a funfair mirror) (6)How clear is your vision?

Final questions (free responses) (1)Which session was most fatiguing? (2)Which session irritated your eyes the most? (3)If you felt headache, which session was the worst? (4)Which session did you prefer?