What you're describing about your rat's eyes sounds like either an infection like Glaucoma (treatable) or cataracts. Rats don't rely heavily on vision (so cataracts would probably not bother them so much) but infections and inflammation like Glaucoma can cause pain and sensitivity and should be treated with an antibiotic/steroid solution such as Gentocin Durafilm eyedrops or an ophthalmic ointment such as terramycin-- a vet would be better suited to choose the medication in this situation if one is needed.

Here's also a list of vets that have done good work with pet rats in case you don't have a good vet already: