The big eye in the original film (the opening shot) was a Big Brother thing, according to Ridley Scott. Orwell's 1984. All-seeing and yet invisible.
That's why Tyrell's building is a truncated pyramid I guess. The top exists, but it's invisible.
So, what about that green eye? I have a theory, but I haven't been able to find a canon explanation, so to speak.
In the original storyboarding, it's a little clearer that the eye belongs to K, setting up the fact that we're going to see the unreal world of this film universe from his literal and figurative perspective.
"The eye is a central image in Blade Runner 2049. Like any introduction, the opening to the film had several iterations, even starting with a more literal depiction of a baseline test inside the firing neurons of K's brain, in a set up that more closely resembled the Voight-Kampff test of the original film. The intention of the above drawings was to illustrate the movement of the camera 'through' the pupil of the eye and into the dream world of the film." ~ Sam Hudecki
Blade Runner: 2049 - The Storyboards
K is nodding in and out of consciousness, periodically opening his eyes and then closing them again as he dozes with the spinner on autopilot. In the storyboard the scene below him would have gradually been reflected in his eye, making it clear that we're seeing what he sees. This seems to have been removed from the final cut in favour of just having a big green eye and then cutting to the eye-shaped solar farm.
