Hello and thanks for your question.
Your symptoms are quiet curious sounding, but also sound very consistent with a migraine headache. A typical migraine headache starts with these shimmering or flashing lights, often times they surround a blurry area or have dots or jaggedly lines associated with them. They tend to progressively increase in intensity and sometimes march across the visual field. Many times this is then accompanied by nausea, irritability, sensitivity to bright lights and/or loud noises. After the onset of the lights (called scintillating scotomas), the headache typically starts and the light show tends to progressively go away.
The visual phenomenon that people experience with migraines do vary from person to person but tend to involve blurry vision with a lighted phenomenon; many people describe them as shimmering, but most consistently is an abnormal lighted visual phenomenon associated with blurring or hazy vision.
One of the less commonly known features of migraines is that many persons can have this visual migraine phenomenon without actually having headache, just having a migraine headache. The spectrum of severity of headaches among migraine sufferers runs the gamut from no headache to severe, debilitating headaches.
There tend to be many varied triggers for migraines, but some of the most common are chocolate, wine and cheese and so your association with eating the chocolate is not out of the ordinary at all.
Many people find that over-the-counter migraine preparations such as Excedrin-migraine work well. The common theme among these preparations is the ingredient of caffeine. There are prescription medicines that can be taken on a daily basis to help prevent them (if they become frequent enough to alter your life) and there are also medicines that can be taken on an as needed basis to help abort the headaches once they start. Most primary care doctors feel comfortable prescribing these, but if not, a neurologist would be a good place to start.
Does this make sense? Do you have any other concerns that I haven't addressed?
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My opinion is solely informative and does not constitute a formal medical opinion or recommendation. For a formal medical opinion and/or recommendation you must see an eye doctor.