I describe it like reading through a straw. I can only focus on one word at a time, while most people can take in more words at once. Consequently, my reading speed is much slower than most. Oddly, it hasn't affected my ability to code; I can "see" code just fine.
Given the representation, I'm not surprised --- a lot of people, including those non-dyslexic, read code very differently from how they read prose: by focusing on tiny sections at a time. I'd guess that if you tried to read code the way you read prose, by trying to see big chunks of it at a time, you'd quickly experience the same feeling.
Just out of interest, does it change by programming language? I imagine all the "structural support" in most popular programming languages would be helpful, but I know very little about dyslexia...