Asteroid hyalosis is completely unrelated to visual snow. Asteroid is a condition in which visible (to patient and doctor) tiny spheres(spherules) of a calcium based crystalline structure firm, in a relatively fixed position within the collagen scaffolding that supports the vitreous gel of the eye. I'm an eye doc, and I have lived with asteroid for 30 years. Etiology/cause is still not fully understood.
Visual snow is a visual processing issue, that rakes place (best guess) behind the eyeball itself, in the visual pathway in the brain. As visual snow is a relatively newly described condition, my first thought is that it may be related to visual processing of information coming from electronic devices. Our retinas respond to light sources by firing the rods and cones, flipping off (think of a Pez dispenser) the next segment that is biochemically reafy to respond. This occurs constantly, and the signal this generated is integrated along the visualpathway in the brain, all thevway to the backnof the brain above the neck, the visual cortex. Along the way', we have pattern recognition neuron arrays, that respond to incoming information. We have something called "flicker fusion frequency", the ability to ignore the inherent on/off nature of capturing tge light response as the "Pez dispenser" rod and cone cells reload the next responding segment. If youve ever been bothered by a flickering fluorescent light bulb it's because it's flickering out of sync and at a speed (cycles or herz) that's sliwvenough for us to see it, not ignore it. I suspect that visual snow is related to constantly, many hours at a time, using electronics: phones, iPads, computers, that flicker and refresh their pixels constantly. Because of this, I'd
suggest that you experiment with eliminating use of all electronic devices for a couple of weeks, get outdoors in natural light, no tv/computer/iPad etc, to see if the brain can do a reboot. This whole issue of visual snow makes me wish I could go back into academia to design some experiments to seek out the true source of the visual snow experience! But I'm retired.