In one of the documentaries he's featured in, Neil deGrasse Tyson talked about the evolution of the eye.
The part that's always intrigued me is this:
Our eyes originally evolved to see in water. ... For land animals, the light carries images from the dry air into their still-watery eyes. That bends the light rays, causing all kinds of distortions. ... Our vision has never been as good since [our distant ancestors left the water to live on land]. ... 375 million years later, we still can't...discern fine details in near darkness, the way fish can.
I can think of at least two world building applications for eyes that evolved in air. In a fantasy setting, creatures that evolved in an elemental air plane, such as the Aarakocra in some retellings of the D&D multiverse, might have very different eyes from ours due to the relative lack of water in their home environment.
In a sci-fi setting, transhumans who want to "correct" our water-based vision to see better might re-engineer the evolution of human eyes.
So, what would eyes that evolved in a "dry" gaseous atmosphere be like in comparison to the ones humans have now?
Edited for clarity:
I'm looking for how plausible and informative the response is regarding the physical structure of eyes that evolved in air instead of water. Thus the emphasis on what they would "be like," and the suggestion to compare them to the eyes we have now.
I specifically left out anything having to do with bacteria in deep time because, while I'd certainly consider such details supportive of the overall answer, the history of how and/or why the structures evolved seems to be its own unique question, and the site generally frowns on more than one question per... question.