Any advice?

Here's a picture I took of Caleb today with my cell phone. This is Caleb looking directly at my cell phone and notice, his left eye is "crossed".
Doug started noticing him doing this about two months ago but didn't say anything to me until Katy, Caleb's speech therapist, noticed it too. He thought he was imagining it because I had never commented about it. I had never noticed it. In all the pictures I've taken of Caleb, there isn't a single one where his eye is crossed and of course, since I'm the one normally reading to him with him in my lap, I never noticed him doing it.
I guess it's only something he does when he's reading or looking at something up close and, it's gotten worse.. He's doing it quite abit now.. Especially when he's tired (this pic was taken right before nap).
Well, we are worried so we are going to take him to a Pediatric Ophthamalogist next month.
From what I've read, lazy eye or farsightedness has been known to suddenly occur in two and three year olds since that's when they really start getting into "reading" books.
Depending on the severity of it, Caleb could just need therapy, or a patch or glasses or, even surgery.
Does anyone out there have a child that has had this problem? Can you tell me your story and what route was taken to fix the eye?
TIA!

ETA: Thanks for the info Michelle, Carli and Zoa.. It was very helpful.