Holidays, Lights, and Photosensitivity

Happy Holidays!

‘Tis the season to be with family, observe the winter holiday of your particular culture, and enjoy the bright flashing lights. All the bright flashing lights. Regardless of which holidays you observe, there’s no escaping the lights.

Holidays can be a concern to people with photosensitive epilepsy (PSE) because the flashing lights and the bold striped patterns of many holiday displays can trigger seizures. Holidays can also be of concern to people with Tourette’s Syndrome because flashing lights can be a potential trigger for tics and tic storms.

Thankfully, the frequencies associated with PSE are reasonably well understood. 15-20Hz is the most common frequency domain, though some people are sensitive around 3Hz. Holiday lights are supposed to comply with health and safety standards before they can be put on sale, so most of the flashing lights you see in the stores should flash at frequencies that won’t trigger PSE. Older lights may still be in use, though, so use your best judgment.

The frequencies that trigger tics are less thoroughly understood. Worse yet, there may not be a frequency dependency at all. It may just be the flashing itself that sets them off. (If you’re a TS researcher, feel free to correct me here, or use this in your next grant proposal! I’d love to see more research along these lines!)

To answer this question for myself – am I sensitive to flashing lights – I decided to do a little experiment. [Insert maniacal laughter sound (Dang it, I really do need to record one of these!)]

In an earlier post about hobbies I mentioned that I do photography. Part of my kit is a pair of off-camera flashes. Mine are considered fairly low-tech since they’re entirely manual. No automatic flash exposure, no E-TTL, nothing like that. Just dial it in and go. But one neat feature they have is the ability to do strobe photography. Rather than just producing one flash of light, they can produce a sequence of flashes. Even better, you can dial in the frequency and the duration. I had neurological testing equipment in my camera bag, and didn’t even know it!

The experiment was simple: Set up one of the units to produce a series of flashes at a particular frequency, and sit in front of it. Repeat the experiment at the full range from 10Hz to 15Hz in small increments. Note my pattern of tics and plot any trends.

Such a simple idea… so many many ways it could go wrong.

To cut to the chase, my tics didn’t change at all. But that’s not to say the experiment was a failure! It simply provided a null result: My tics aren’t sensitive to flashing lights. But in the process I learned something even more important…

Don’t stare at a strobe light! It’s stupid!

By the end of it my wife was almost rolling on the floor laughing. “What were you THINKING?!” At that point I was wondering the same thing, myself.

So let that be a lesson to you! Science is dangerous!

No, that’s not the lesson. Science is just a systematic way of trying to answer questions. The real lesson is this: At times we find ourselves in a situation where we have to be our own advocate, our own expert, our own principle investigator. So by all means do your own research so you understand YOU. Just be safe about it.

And don’t stare at a strobe light! It’s stupid!


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