As a kid, I used to think I could "see molecules" thanks to the grainy dots in my field of vision. Now, of course, I know that's not true, but those dots persist — and I've still always wondered what they are. Sometimes they're so noticeable that I'm convinced there is some sort of dust cloud forming in my apartment. (To be fair, that is a legitimate concern, but is not the case here.) It turns out what's really happening is that I have a puzzling condition referred to as "visual snow," and researchers are just barely beginning to learn, well, anything about it.
"The typical [visual snow] patient has a continuous visual disturbance that looks like an untuned black and white television," says Peter Goadsby, MD, PhD, a neurologist at the University of California San Francisco, and one of the few researchers studying visual snow. People report seeing little dots moving around in a grainy field, usually dark spots during the day and white, snow-like spots at night. Many also have a sensitivity to light and see persistent trailing afterimages, glares, and other odd, annoying things in their normal vision. But the graininess is the constant.
Usually, people will say they've had their symptoms since childhood or "as long as they can remember," Dr. Goadsby explains. Although the condition is not harmful or painful, it can be intrusive enough to make your life more annoying: Some patients complain that their symptoms are much worse while using a computer or phone before bed, while others report that their snow makes it difficult to drive (especially at night). People who experience visual snow seem to be more likely to also have migraines, and the two conditions tend to exacerbate each other, research suggests — especially when it comes to migraine auras.
Other research links the symptoms of visual snow to those of hallucinogen persisting perception disorder (HPPD), a condition that some people develop after experimenting with hallucinogenic drugs. But Dr. Goadsby says the majority of visual snow patients haven't used those drugs. Still, the connection suggests that visual snow and HPPD are operating on the same neural circuitry, which mainly involves the neurotransmitter serotonin.
And that's about all we know about visual snow right now. "It’s not so long ago that it was really considered just more or less craziness," Dr. Goadsby says. "It hasn't been in the medical consciousness for a very long time." But, in the absence of research, patients have formed online communities to help each other figure out what's going on (and tip each other off to ongoing studies). Personally, I first realised what I was dealing with when I checked out the r/visualsnow subreddit and the patient-run site Eye On Vision.
Considering how little knowledge we have about what the condition is or why people get it, it's probably not super surprising that we also know very little about treating it. Right now, Dr. Goadsby says doctors may prescribe antidepressants or medications used to control blood pressure or epilepsy. These may reduce the symptoms for some patients, but there's nothing close to an established treatment regimen.
To that end, Dr. Goadsby and his team are working on a project to pool what treatment data we do have, in order to start figuring out which options are worth looking into more heavily and which ones we can stop wasting time on.
For now, though, we're stuck waiting and watching the snow — or the molecules, if you prefer — fly by.