OK, bit of an update:
It's been three days now and symptoms have definitely subsided. They're still lingering but it's nothing too bad. I imagine at this rate I'll be clear of exacerbated symptoms in a few more days.
As I mentioned above nutmeg contains myristicin which can be found in many foods including many nightshades which I've already touched on in a post here: http://hppdonline.com/index.php?/topic/5431-nightshades/#comment-34336
At this point I don't think there's even a question -- if you have HPPD you need to stay away from nightshades! These foods clearly contain multiple chemical agents that exacerbate HPPD. If you're someone who eats potatoes, tomatoes, peppers and others spicy foods on a regular basis then these are likely only making your condition worse.
Additionally, myristicin can be found in many over-the-counter drugs, including antidepressants and antipsychotics. Here is a full list: http://emedicine.medscape.com/article/812644-clinical#b5
One of the above mentioned medications is an antihistamine called diphenhydramine. Last year when I couldn't sleep I took a few pills of this substance and noticed an immediate worsening of my symptoms the next day. I made a post about that which you can find here: http://hppdonline.com/index.php?/topic/5091-diphenhydramine/#comment-31926
In fact, if you search this site's database for "diphenhydramine" you'll come up with over 90 results and posts similar to mine wherein people get HPPD from this same drug. Here are a few:
Myristicin is known to cause what's called anticholinergic toxicity syndrome. This is actually a somewhat common condition wherein people show up to the ER with a variety of symptoms including hypertension, urinary retention, tremors, dry mouth and skin, altered mental status, etc. However, the range of symptoms is quite large and also includes the following, which as some on this site have already noted, overlap with those of HPPD: pupil dilation, light sensitivity (photophobia), blurred vision, double vision, loss of accommodation and inability to focus on nearby objects (cycloplegia), tendency to be easily startled, memory problems, inability to concentrate, disorientation, brain fog, periodic flashes of light, visual snow, tunnel vision, warping or morphing, squiggly lines, patterns on surfaces, etc. Here is a full list: https://en.wikipedia.org/wiki/Anticholinergic
One thing I've found interesting about neurotransmission when my symptoms have worsened is that it's often due to a lack of a transmitter. In caffeine GABA uptake prevented. In nutmeg and other myristicin it's acetylcholine. And if you go back to the original source, LSD, it's serotonin. In each case, as far as I can tell, there is a prevention of neurotransmission that causes HPPD symptoms to manifest. Would this not then suggest HPPD could be rooted in the brain's inability to absorb and or process certain neurotransmitters?
I don't know much about this stuff so perhaps if someone else does they can chime in. Regardless, stay away from those nightshades!
There is some excellent advice in these replies. There are a lot of bright people who post here. I'm not counting myself as one of them (:
Seriously though, anxiety is something that can magnify any underlying issues. Then the anxiety can make those issues worse causing a cycle that makes the anxiety worse and worse and making whatever issues you may have seem bigger than they are. Hppd is no joke, but by itself (at least for me) it's something I can live with. The anxiety was something I had to resolve or my blood pressure would have made me real sick by now. As the other replies say, deal with the anxiety. I couldn't do that until I was sober especially refraining from cannabis because, for whatever reason, it causes major anxiety in some people.