It’s said that the action of opening the eyes wide that reveals more ‘white’ gives a number of clear signals to others.
In the primates animates domain, it may signal fear and in various contexts this may indicate subjugation, surprise or just terror. It’s often used as a quick visual cue in performance and can trigger laughter if used skilfully to signal something happening suddenly or an unexpected surprise. As in all things pertaining to comedy and particularly performing comedy skills; timing it all.
In the ‘wild’ the subtly of the cues are extraordinary. In the top example the white above the pupil is clearly showing but not below. The eyes are engaged with ‘us’ so we know this person is slightly below our eye level or their head is tilted back. We would know which from the overall picture in real life. If the white was visible under the pupil as well we would know this person was in wide-eyed mode and

No eyes were harmed in taking these images. Posed by models.