Scotoma after exercise

So this evening was the second time in two months that I've experienced a scotoma.

"5th November 2016. After weights exercise, a visual illusion to the right of central visual field (both eyes separately). A flickering jagged arc. This is consistent with a scotoma. Same phenomenon with either eye closed. After half an hour it began to move out and enlarge while retreating further into peripheral vision. After an hour it disappeared.

This phenomenon reappeared 19th January 2017, a couple of hours after fairly intense exercise, at 6.10 pm. Visible duration 20 minutes. Started at the centre of the visual field, a flashing-lightning V-shape with vertex at 8 o'clock. Gradually got larger until it vanished past the boundary of the visual field.

Other relevant information: I skipped lunch today as part of my weight-control programme."

After the first time I checked with Wikipedia to discover scintillating scotoma - it looks like this:

although as mentioned I'm seeing a well-defined white jagged shape, growing slowly in size.

I'm not the only one. A google search for "Scotoma after exercise" returns this.

"f you read the title and opened this post, you most likely do suffer from Scintillating Scotoma. You know, start to lose part of vision because of a flashing spot .. . The flashing zig-zag moves to outer edge of eyes, then, after 20 minute or so, goes away.

The common consensus is that is a migraine headache, without the pain.

Anyhow, since I started upping my intensity on the bike trainer workouts, I seem to be getting them after each workout. Could it be clustering since the intensity is greater? I used to get them sometimes after early season races, then as the season wore on and I got used to the intensity, they went away.

I know they're not really an issue, but, hard not go to into a mini-panic each time. "

Wikipedia talks about "cortical spreading depression" as the cause:

"a wave of electrophysiological hyperactivity followed by a wave of inhibition. Spreading depolarization (SD) describes a phenomenon characterized by the appearance of depolarization waves of the neurons and neuroglia that propagates across the gray matter at a velocity of 2–5 mm/min.

SD can be induced by hypoxic conditions and facilitates neuronal death in energy-compromised tissue. SD has also been implicated in migraine aura, where SD is assumed to ascend in well-nourished tissue and is typically benign in most of the cases, although it may increase the probability in migraine patients to develop a stroke."

I don't suffer from migraine, and the effect is purely visual although if pressed, I might admit to an ill-defined feeling of 'headiness' which persists for rather longer.

It seems benign and not a precursor to anything serious so I'm inclined to see it as no more than a warning to ease up a little on high-intensity training, which is currently sending my pulse north of 156, close to the maximum heart rate (207 - 0.7 * 66 = 161) for my age.

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Apart from any intrinsic interest, I put this post up to compensate for the lack of engagement many of you feel for my science posts - such as the one posted earlier - fascinating though they are 😐 ..

Roy asks in the comments how I know this. Family verbal feedback and - to an extent - view counts.