Interesting topic
I personally see little transparent "cells" when light is intense, it's like i'm in an aquarium, but I never really cared about those, always thought it was some kind of normal "dirt" in my eyes...
The reason I'm here is to bring new information about the "darting specks of light" thing, I've had them from around 25 to 35, and I practically totally stopped them appearing, willingly, simply by being careful to notice when they do happen (I had to stop them because nobody knew what I was talking about and I started believing my brain cells were dying abnormally, and i'd end-up doing dementia or something, which is probably a wrong assumption, but you never know...)
I would say they appear (for me) when I quickly pass from a high concentration-minimal breathing, state, to a high effort (can be mental) state, the trick is to be aware of it, like unconsciously, and that's all. Nothing really changed in my life for preventing them, i still jump from my computer to run at the tea I forgot on the stove, but jumping from my computer to take a solid shit is a no-go, I must be aware the specks will happen, then my body attitude will "magically" adjust itself to prevent them, i think the trick is some mental clue to the heart along with normal breathing. Strange isn't it? Probably it got something to do with blood pressure.
It took me a lot of trial and error to find-out how to stop them appearing, but I passed from once a day to once every 2-3 months, high intensity and duration to low intensity and duration.