What is wrong with my pet rat?

My rat Daisy was the most energetic rat i have ever seen. whenever i would wake her up from a nap and she would be perfectly calm but literally 30 seconds later i wouldn't be able to hold her still. recently (sometime i think in october or september) her sister got a tumor. its been getting REALLY big, but its not hurting her and I'm pretty sure its just a fat tumor. but I started to notice about a week ago that Daisy hasn't been as active. now as i am typing this, she is just siting in my lap, only moving about my legs slowly. she doesn't look like she is eating as much as she used too. I don't know if this is related to her sister having a tumor or not. ive also seen that she has been getting a dark red crust around her eyes. everyday after school i will have to take a wet washcloth and wipe it off (with great difficulty) in order to open her eyes. but even then 5 min. later i will see it forming again. i have almost positively identified that she has gone blind in the last 4-6 days because i held her right in front of my cat and she didn't freeze up like she used to. and by that i have also determined that something is up with her sense of smell. A few more incidents that might prove weather or not she is blind is, just a few seconds ago, she lowered herself off my leg with so much caution it looked like she thought she might drop to her death. then when she was off my leg she stepped onto the very ege of my chair and fell off. if she could see fine i think she would have seen that the edge was right next to my leg. I also just set her on my floor, and usually when i do that she bolts to her cage (with that cute little jumping run) but she didn't even go in that general direction and she just kind of waddled along. Im really worried why she suddenly went blind and am very concerned for her health. i don't want to lose both my rats to painfull health problems. Is it possible that she has glaucoma? PLEASE HELP