Those pictures are very like the 'visual disturbance' I had on Sunday, first I have had for many years. In the right field of view, angular like the drawing, but sparkly, like a kaleidoscope.
Lasted for about half an hour. No headache or nausea, but felt a bit 'woozy' for a couple of days afterwards.
Seems to follow a late lie-in of a morning (which I rarely get now!) so may be associated with dehydration. I cut down on tea intake too during woozy period, just in case there is an association- but I'm not giving up tea altogether!