Our old housecat went blind a bit over a week ago. It was sudden and unexpected. She's been around for about 15 years, and she turned up as a stray of unknown age, so we have no idea how old she really is.

There is no obvious evidence of physical injury, and no known access to toxic chemicals. Our best guess is either some sort of concussion, or a stroke.

Her eyesight seems to be returning. She squints when bright lights are shined in her eyes, and today she appeared to follow a red laser dot on the floor in front of her paws, batting hesitantly at it a couple times.

Any idea what the cause might be, or how we should continue to treat it other than keeping her inside and away from heights?

edit She has been to the vet. She went the day after we noticed something was very wrong, and she was bumping into things and walking off-course when headed for the door. The vet said it was probably neurological, and there wasn't really anything she could do.