I have a 12-year-old cat who randomly goes blind. I've only had him for a little over a year, and this started about 8 months ago. He was in rough shape when I adopted him but he's gained weight and is doing wonderfully now, except for this. It happens once every 2 months or so, and usually at night. He can't see ANYTHING--not even shadows. It doesn't matter whether I turn the lights on or off. I usually turn them off because I feel like it has to hurt his eyes when they're super dilated, but he doesn't wince or back away from the light when it's on. He runs head-first into things, including me, and paces around, just kind of turning his head in all directions and trying to figure things out. The first time, I rushed him to the ER and waited two hours. He was back to normal by the time we got to see a vet. His blood pressure was normal then. I then followed up with a second vet and took him to an ophthalmologist. The ophthalmologist said his blood pressure was slightly elevated and they started him on Amlodipine, but she determined that the blindness is NOT caused by his blood pressure. She said his eyes were absolutely perfect and his retinas looked great. If this was a blood pressure issue, she said there would have been some evidence of damage to his retinas. The second time it happened, I took him back to the ophthalmologist and she again saw no damage to his eyes. She recommended a $4,000 MRI for him. I'm happy to spend that money if something positive comes of it, but I don't quite see the benefit yet. If the MRI shows something, it will probably be a diagnosis that's untreatable. I've also been told that this doesn't sound like a brain tumor since it's not progressively getting worse and he has zero other symptoms. It's just like someone turns the lights off for a few hours and then back on. The third time it happened, I monitored him overnight and he was better by morning. A few days ago, he went blind mid-afternoon and it lasted through the next morning. This is the longest it's ever gone on, and it's never happened in daylight. I took him to a different vet that I really trust, and he was also stumped. Unfortunately, his eyesight returned by the time we arrived so he didn't get to see it in action. But he confirmed his eyes were clear, his retinas looked great, and his eye pressure was perfect. His blood pressure was also spot on. I showed him the attached picture of what he looks like when this happens, and he said it's rare for a cat's eyes to be THAT dilated. He did bloodwork for his thyroid, kidneys, blood sugar and liver, and all of that was normal. He's medicated for hyperthyroid. The next plan is to rush him to my vet when it's happening so that he can see it in action. No one has been able to do that yet. But that's going to be hard since the only vet open at night when this happens is the ER, and they don't seem to know what to do with this. Does anyone have any ideas? Here's the photo from the last time it happened.