Screenreaders usually break it down into chunks it can pronounce or spell it out character by character, with added cues to indicate punctuation and some other things. It's not as slow as it sounds though, most blind people have their screenreaders set to read at a speed that is totally incomprehensible if you're not used to it. It requires a very good memory to manage something like programming, but blind people get really (almost unbelievably) good at that sort of thing simply because they practice a lot by necessity.
I imagine, if you can comprehend at a very fast speed, it gets easier to keep the line in your head. As you can store and revall the characters from the very short term memory. I don't know if this phenomenon exists, but if I,'ve heard the entire line in for example 0.5 seconds, I think I'll be able to construct a mental image of it and code.
Another point is that I imagine it takes your complete focus to listen and comprehend single characters at such speeds, so you will be super-focused on the task when you're writing code.
We, as the programmers with sight, can read code without getting anything out of it, if we're not focused.
