Don't know if you'll make it back this way, but just in case and for the benefit of others that'll come this way...
The following are a list of other names this particular visual symptom are called by:
If your husband would do a little test he might find that the light arc that 'grows' within a visual field is actually only in his one eye. The visual field of each eye overlaps into the other. If he looks at an object, so that it fills 80%, with only one eye open and relatively centered in that eye's visual field (does not have to have a migraine aura in progress) now...not turning the head at all, close that eye and open the other. You aught to be able to see that object entirely, with the opposite eye. So that even when the eyes are closed the 'trapped' light in the one eye is still filling a shared visual field. The brain still perceives the whole visual field even in the deepest part of the eyeS. There's a cone in each eye, and the one tip side registers the same data field as the mouth of the cone, just makes it smaller on the inner tip end. Probably to fit it all into our little brains. So you have a growing little light on the inner most part of the one eye while the brain registers a shared field from both eyes (much of it overlapping). You won't find a double vision of the exact same shape in both eyes, from what I could gather from people's reports, if it's in the right eye,it'll be strongest on the right side of the eye (3:00) if it's in the left you'll see it strongest at 9:00. Some have a full circle or almost, reportedly in one eye.
From what I can make of mine, the light that is normally received and organized by the optic nerves regarding depth of brightness/darkness and contrast (as well as color etc) is for some reason condensing, refracting or absorbing within some kind of 'crystal' that burns out after a few minutes.Except mine alway grow from approximately if not the exact same place. It certainly arcs the same way and in the same direction. Even the same as last year. Counterclockwise from 4: to 11: (approximates at their highest intensity) However,their intensity/magnification isn't always the same.
Anyway, the overlapping of the visual fields is why it appears to be in both eyes even when our eyes are shut. (That's why I mentioned absorbed, as obviously, something is retaining the light that comes in through normal optic functions but that in striking that particular area, I'd say deep within the eye and just a very small nick, but as it's 'light' grows it is sufficient to start to overwhelm the visual field of the affected eye near the 'gate of sight' 'center of the eye' whatever.... Maybe it's a light censor getting overexposed. As though a filter grew too thin.
I'm sighting my observations in the hope that someone with a better understanding of optics might be able to use this. Supposing this is NOT at all related to Transient Ischemic Attacks (TIAs) and it's been ruled out.
So if you can confirm any descriptions I've given I'm sure it would help.
I do not get headaches with mine, and I seldom have ever have had them. I really don't like using the word migraine even if the cause is from the same problem. It certainly is a different symptom from what is commonly known as a migraine being a headache. There's a little eye ball pain, but that's only occasionally, sometimes it's photophobic type of pain(at it's max-too much light) Maybe it's all photophobic pain just lingering in a duller level of pain.
My aura's started last summer. Only one every now and then...nothing all winter and spring, and now they're back. Either sunlight or computer moniter seems to get it started, even if only in from the edge of eye field. It seems much brighter if bright light is 'feeding' it. Not half as bright and colorful when the eyes are closed. My colors don't move as I've heard some report but they do bend into the edge of the triangles (cross section of a cell?) I've had 4 or 5 in that past 2 weeks, which is really unusual and has me a little tense now. I'm one of those people that have to be laid out by something before I'll own up to it to any doctor. My aura's start small as all do...and the arc grows to fill a large portion of the field. Mine have definate triangles with all 3 sides, (no open bottom-thus other's zigzag description)they are arranged side by side, the next one flipped in the opposite direction and joined to another triangle again flipped to be the opposite direction. So there's a zigzag within but definately mine has edges bordering the zigzag, similiar to a path with a zigzag drawn lengthwise in between. An analogy - A slightly spiral (arc) staircase made with triangles(bent/distorted/reflected light). Generally all triangles are the same size, but do taper off to be smaller, but is never so magnified as the shapes in the first 4/5ths or so grow to be. Now there's a mind teaser for somebody.
Anyway, here's some links I think would be of help, though I lost one (thought I saved it) There's lots out there. Though I would search out:
scintillating scotoma pictures
If you think it's a particular food, eat it again and see if it is the instigator. However, a food or edible/drinkable substance might still be the instigator when combined with onset of other physiological problems/symptoms such as high blood pressure with salt etc. I don't think it'd be easy to track down this way unless somebody out there does some trials with a few suspects in mind.
Just when I thought my long wind had come to it's end... Relevent to note: I do have a tiny blind spot (not the usual one) which is actually a relatively dull light spot in the very middle of the affected eye. It is a result of looking at an solar eclipse when younger...no wise guys around those days. It only blocks out a letter or 2 when reading but it is a white spot over where the letters should be. Hard to read with just the one eye if I had to. Anyway, might explain why I have borders on my zigzags. Who know...
There are other details, but what is crucial has been said without perhaps stepping into symptoms from other problems I have or am expecting to have with currently known diseases or medication usage.
Hope I've been of help, Sandra