If you've seen Oblivion, you might have noticed that Vica/Victoria, the character played by Andrea Riseborough, Jack's (Tom Cruise's) partner has permanently wide open pupils, or dilated eyes. Why is that?
If you've followed the reddit conversation mentioning this, in my opinion, there's one user getting it right. But for me, the biggest clue was in the Oblivion Making-Of/ Behind-the-scenes footage on the Bluray: there we learn that the "tower set" was completely practical, no green-screen. The above the clouds horizon vistas were photographed by a splinter unit (or Mr Kosinski himself) on top of "a moutain" as Cruise says on the commentary - probably on Mauna Kea - in Hawaii. The resulting imagery was then front projected onto a 360 degree screen on the tower set, to allow the film team capture acurate lighting hues and reflections in the all glass architecture of the very Pierre Koenig/ Stahl House "Tower Set".
So here's my explanation
They used fast lenses and the very sensitive F65 camera on this show. With that equipment, they were able to photograph with very minimal lighting. The library scene, and elsewhere - part of the look for this show - natural light. In the Jack/Victoria dinner scene, there's very much of Barry Lyndon in there, with only a candle lighting the scene! Now, in all "Tower daylight shots", the only lighting on set was the reflected light of the beamers projecting the 360 degree cloud backdrop - and that is very low light. Imagine, you in a room, only illuminated by a slide projector, or a video beamer - that's not a lot of light. And although they used a couple of beamers to achieve the all-around vista, it was quite a big room that had to be lit - so that evens it out again.
And then, some people react to light differently from other people. Ms. Riseborough's reaction was: wide open dilated pupils. I mean, in comparison with other film sets, this set was dark. Normally, film DPs would tend to light a set well, and if needed dim down in post. But this here were dark scenes, which would tend to appear lighter in camera. I may be later on the conversation, with some clues on reddit, but I also second Hunter with his take on the eyes detail - while adding my twist "it's camera sensitivity": just look at the focus, it's not as shallow as you would expect with wide open lens apertures... Anyway. There you have it: for us, the scenes look like daylight or sunset on screen, but they were actually low light on acquisition.
After all this technical babble, there's also an artistic effect of these eyes - a favourable one. Many viewers described these pupils as having an offsetting effect. A bit of Blade Runner. It made them feel not at ease with the Victoria character. Why? Well, watch the movie - if you haven't already.