My dog is 12 years old, she recently went blind within the last three weeks.?

She never does any activities or anything to make her hot but when she is just lying there she suddenely starts to pant. I have try to give her water and she doesnt want to drink it. But she will shack really bad when she is panting and she will stop and start randomly. I am really nervous that she is in pain. What do you think is wrong with her?