I just got my first pair of reading glasses. My left eye doesn't quite make it around to the thing I'm focusing on, which causes me to work harder to make a reasonable stereo image of something close to my face (this condition has a name, but I can't remember what it was). I've apparently been compensating for this problem without really knowing I had it. At the beginning of my last visit my optometrist did a couple of checks and then asked: Do you find it difficult to focus, or that sometimes you see a double image when you read? Do you get tired while reading? Yep. All my life. I'd never really noticed the first thing until Mrs. Transient Gadfly pointed out that I close one eye when reading in bed, which was apparently my main compensation mechanism (it works only passingly well, as I fall asleep almost comically fast while reading anyway).
So now I have glasses with a slight prism in the left lens (the other option was 12 weeks of vision therapy, which I'll probably try some day when I don't have an 18-month-old). The other thing my optometrist mentioned, almost in passing, was that this would help my reading comprehension. As long as it has mattered (a little bit in high school, mostly in college), I've known that I don't absorb anything by reading it. I can follow a narrative, but my reading comprehension is for crap. I have adapted to this fine in life; on the verbal portion of standardized tests I read the questions before reading the paragraph; I figured out that I have to write down notes on the material if I want to know anything about it when I'm done.
Are these two things related? I haven't had the glasses long enough to know if they're going to help me glean new meaning from the text. But I'd always assumed that my brain just wasn't wired to learn by reading, never once thinking that it might be because my eyes were draining all my battery power just trying to stay focused on the words in front of them.