Every few months, one of my eyes does something weird. It clouds over until its completely black and I can't see anything. Then after a minute or two, it starts to clear, and my vision returns to normal. (This is what it looks like to me - I have no idea what my eye looks like externally while this happens.)
I mentioned this to my optician last time I had an eye test, and he didn't seem interested. Does anyone know what it is?