Originally posted by WPRESTO Another visual event that can be scary the first time it happens: You suddenly see irregular rippling patterns, sort of like lightening bolts but within them it looks like shimmering heat waves. If they are off to the side of your visual field and you shift your eyes to get a better look, they move with your eyes as if they were attached to the retina, which in fact they are. Nerve cells just go screwy for a while, possibly caused by sudden contraction of blood vessels serving the retina, but they will settle down and the patterns will disappear in maybe 15~25 minutes, almost always in less than an hour. Totally harmless, not indicative of any acute or chronic problem that needs attention, but scary the first time they happen, more so when they recur and you haven't learned what they are.
If that happens to both eyes in the same time it's a "visual migraine", an electrical disturbance. I get that around once a year with no apparent pattern to what triggers it. In my case it starts like a kaleidoscope pattern at the edges of my vision, working its way inwards over 5 minutes until I have very narrow tunnel vision, then clearing up in reverse over the next 15 minutes. This is the aura that precedes a painful migraine headache but in my case I just get the aura without pain.
I completely agree that the first time is very scary. I thought it might be a stroke. I asked coworkers if my speech was slurred, and started picking up heavy objects to make sure my arms were working okay.
If it only happens with one eye it's called a "retinal migraine" and likely caused by a blood flow disturbance.