Squinty eyes: cause for concern in 4-week old RAT

I'm going to be adopting some rats from a rescue group soon. The foster mom told me about her favorite rats (ones with the best personalities), but one of the faves has what she describes as slightly "squinty eyes". He's very friendly and seems totally healthy, but his eyes are a little squinted, whereas his brothers' are not. (I haven't seen the rats myself yet).

The rats are 4 weeks old, so it's not like they're too young to have fully open eyes. So I was curious what, if anything, might account for this one boy's eyes to be kind of squinty? Should I be worried, in terms of his vision and/or overall health? Or is this just a benign little quirk?

(I wanted to post this in the Ratties community at LiveJournal, but LJ is having major problems. I haven't been able to post or comment for nearly 48 hours, due to the fallout of a stupid DDOS!! Looong, confusing, horrid story; please see my previous Yahoo Question if you want to know more). :(

Thanks all! :)

Contrary to what others are saying I have never seen 4 week old babies squinting, and I have bred and kept several litters in the last 11 years.

Are his eyes squinty, or are is eyes abnormally small? Rats that are born blind will have small eyes. Don't let this concern you. Of it's 5 senses, a rat will depend on it's sight the least. Rats have very poor eyesight to begin with and depend the their sense of smell and touch (whiskers) the most. A blind rat can act perfectly normal, so you may never know it.