Older rat has squinty eye.

Question
Hello.

My oldest rat, Yoshi, is squinting her left eye. She's pretty up there in age (approaching 4). When awake, she's active. She still eats well when hungry, but is much more picky what she eats. She'll eat a little bit of something, then want something else. She sleeps a lot (I'm figuring that's from old age) and has been breathing quite heavily for about 4+ months, since Bob (another rat) died. Her balance is a bit off when climbing, but not so much that she can't go up and down her ramp & climb the cage. She seems to be losing her ability to grip a bit.  

I'm guessing her weakness (she gets along fine, but slower than she used to) and other symptoms are from old age. Some days are better than others. She can appear to be on death's door in the morning as of late, then be very active during play time at night. Her life is probably winding down. However, the eye squinting is new from the past 2-3 days. If there is something I can do to make her more comfortable, regarding the eye, I'd like to know.

I've tried to give as much info as I could.

Thank you.

Answer
Yoshi is a grand senior rat, thats for sure, and some of the things you describe do point to old age. However, the rapid breathing may be due to heart disease which of course could also be a part of old age too, but just to let you know that it can be treated with medications. You can read more about that here:

http://www.freewebs.com/crittercity/heartandkidneydisease.htm

Now for your original question (I tend to babble in different directions! LOL!!) , the eye squinting can be seen in rats that have eye irritation,perhaps a scratch on the cornea.  What type of litter do you use? Sometimes even litter such as aspen can get in the rats eye and scratch the lense a tiny bit which causes some pain and burning, thus in turn the rat squints.  Is her eye running?  Is she rubbing it at all?
You can bathe it with a warm damp cloth to help but do check for swelling. If you have saline solution you can even put a drop of that in her eye. Contact solution with no preservatives is fine to use in this case since it is sterile as well.