eye health

Question
We have 2 male rats, about 6-7 months old.  Both have been in good health & are well cared for.  In the past 3 days, I've noticed that Pablo's right eye looks smaller than his left.  It seems less shiny & closed a bit more than the other eye.  He moves around quickly, so it is hard to tell if it is also cloudy or I'm seeing a reflection of the light.  It doesn't have any discharge- mostly a size difference.  He's eating and active.  Any ideas?

Answer
could this be a birth defect you never noticed before? I have a little girl who has two different sized eyes and its just that she was born a bit defective. Watch for any discharge and  behavior change, and if you think it could be the beginning of an eye infection, take him to the vet for a looksie.