User blog comment:Argonash11/Why can't Quarians have see-through visors?/@comment-4523622-20111013164237

I personally think that, after living on ships for so long, their eyes can't adjust to normal sunlight on any degree anymore. Considering how weak their bodies are in the first place (weak immune systems and the like) I could see this as a possibility. I mean, we have a hard time adjusting our eyes going into a bright sunny day after spending a good chunk of our time in a dark room. I figure it's the same effect.

But that's my opinion. Probably Bioware couldn't make up their minds on what the Quarians should look like so they made the visors hard to see so they could come back to it another time...