I am an ophthalmologist, so I guess it is kind of my job to try to answer this one
First on the defensive side, I presume you see a PCP occasionally, and aren't experiencing any other systemic symptoms. What you are referring to medically called "entopic phenomenon", with some of the big hitters as possible causes....with this said, the fact that you report it all your life makes a difference. Things like MS, cranial compression, or other very serious things are found with this symptom, so it's good to know what it's NOT to start with.
More realistically, it is likely a neurological synapsal issue that is more physiological that pathological. In many cases of Asperger's, Raynaud's, and some of the X-linked genetic diseases, it is thought that there is insufficient axonal tone in the areas of the visual cortex that work to filter out the "white noise" of your vision.....in other words, the "push back" of some of the visual processing can be interfered with, especially under certain conditions.
It is benign, and somewhat common, under these circumstances.
-- Does your vision have a noticeable pattern where this occurs, and does your vision ever worsen....I don't mean the snowy vision, I mean reduced acuity, blur, under certain conditions....I would especially pay attention to when you exercise, so-called "Ulthoff's Phenomenon" that is pathoneumonic for MS.
-- Is it in both eyes or just one?
-- Have you had an electrodiagnostics done, such as a VEP, visual gradient, or otherwise? This would be the only true method of determining if there is neurological pathology.
Hope this helps. Let me know if you have any questions
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