my personal headcanon to what exactly is under cait's eye patch. I've seen a lot of people who think she basically has heterochromia with a neat lil scratch going perpendicular to her eye, even tho the spear clearly cut along the eyelid. also, a spear slashing through your eye is not gonna make it change the color of the iris. what probably happened was- the eyeball was damaged to the point of collapse, and its remains had to be removed. so what we're left with is
she's got no eyeball. i think the eye patch makes much more sense that way- for one, seeing an empty eye socket might be considered unpleasant, so she mostly keeps it covered. second, you can see how snug the eye patch is- it sits tightly on her eye socket, and i imagine that if there was an actual eye there, blind or not, it would get really irritated having a piece of fabric rubbing on it all day.
as for a prosthetic- i honestly don't think caitlyn cares about looking "normal". she probably won't get a functioning (fictional) hextech eye to fix her sight- i think she believes this scar to be a reminder for her past mistakes, so she never "loses sight" of what's important ever again. a prosthetic for aesthetic purposes feels a little ooc. caitlyn never cared about being pretty. i don't think she's shameful about her scar, nor does she wear it with pride. i think she's pragmatic and neutral about it, her biggest concern being "but can i still shoot" and the answer to that, i think, is a "yes". the rest is peanuts for her.
the upper eyelid itself is still in tact, and it healed kind of roughly, so the scar looks mingled (caitlyn could probably have surgery to fix it, but like i mentioned, she doesnt care for that stuff). i also think her tear duct is still working perfectly fine, so when she cries, she tears up on both sides.