This happened to me a couple of days ago in a very short LD.
-I became lucid
-immediately my vision became blurred and unfocused. I then tried to focus my eyes, but instead they went crosseyed, and the vision sort of sharpened, but it was like loiling through two pairs of glasses whose prescription is very different
-due to the lack of sight, the dream continued for about 10-20 more seconds, then ended with me waking up crosseyed.
How can I solve this problem?
I don’t know, but it does answer a question someone else once posted: “Can I look crossed in a LD. If not, can I use that as a RC”. Apparently that would answer be “NO”, since that is clearly possible. 
You could try shouting “More clearity”, take a “clearity pill” or put on some glasses. If you believe it will work, it probably does.
I can’t explain it, but I can say that I’ve had similar experiences. My impression is that it is not just a quirk of the dream, but actually is caused by something physical. It just feels like it is forced somehow. Some of these experiences with visual problems turn out to come from having an eye open while sleeping. It’s odd though, that I can’t remember a single one in which I was not lucid.
I’ve had similar problems. For me, it’s not the cross-eyed thing, but rather as if there was something on my eyes, forcing me to blink repeatedly or just blurring my vision.
I found, in a recent dream, that putting on my glasses (or rather, in that case, changing the ones I was wearing for another pair) seemed to help, but it wasn’t a final solution, as I still couldn’t see that well.
If anyone has any hints, I’d love to hear them too 
Hmmm…
Well thanks for the help, I’ll try those things next time.