Thanks for that. Chalk this up to yet another thing that I thought everyone had but it turns out isn't universal. For me regardless of whether I've been exposed to light whenever I close my eyes there's a permanent lava-lamp type display going on. It can be quite entrancing at times, although if I'm not tired it, combined with my tinnitus, can keep me awake. Sometimes the patterns repeat, sometimes not, but they are always there. It's similar to the blobs you get after looking at bright lights but they are there all the time, even if I've been in darkness the preceding few hours and move in the exact way a lava-lamp contents do. This has been the case as long as I can remember.