Short-lasting partial blindness and deafness

I’ve been wondering about the cause of something that happened to me a few months ago, that I’ve never experienced anything similar to before or since. I was out walking, and overall felt completely normal. My vision started to quickly turn blurry in a sort of pixelated looking way, and it looked like the light was dim. At the same time I also got a very strong headache, and became almost deaf, while hearing a high pitched tone at the same time. I did not faint somehow, but I sort of just stumbled around. This only lasted about 5-10 seconds, before I quickly started to feel normal. There were seemingly no lasting effects after.

I’m 22M, in good physical shape. I eat mostly healthy, and exercise regularly. I have adhd and cyclothymia, for which I take lithium. I don’t have any history of serious physical illness.