Hello, and welcome!
I'm so sorry to hear about this new symptom of blindness for Midnight. I know how disconcerting this is for you and her.
Older cats can be more prone to this and it could have many possible causes. She could have high blood pressure and this caused a sudden bleed into the interior of her eye, or she could have experienced a trauma to her head, unbeknownst to you. Here is more information:
Sometimes, blindness can also be caused diabetes, or certain medications, so discuss that with your vet, as well.
She really should be evaluated in person by her regular vet who can do some senior blood tests and might refer you to a veterinary ophthalmologist, if necessary.
For the moment, continue to help her find the litterbox, her food/water, her bed, etc., and don't move the location of any furniture. Blind cats can get around the house with little trouble, once they establish the location of everything and get used to it.
The fact that she has lived to this fantastic, advanced age, is due to YOU and the wonderful care she has always gotten!
I hope all will be well with Midnight and please keep me posted on how she's doing and what the vet tells you. Thanks!
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