Hi. Some Months Ago The Top Half Of What I

Hi. Some months ago the top half of what I saw was pixilated ( actual squares!!) it lasted 20 minutes. Today I had something similar, but in long narrow lines at right angles, with a hook at the end. Inside where lines flashing on and off in black and white. It started, got worse ( stronger) and then moved outwards. I checked and it was the same in both eyes. It lasted 15 minutes and finally went when I lay down, after 3 or minutes. I had a very slight headache after.