Over the years, I’ve come up with a few little sneaky tricks that others might have missed. It’s amazing what you can figure out if you keep an eye out for things that are interesting, (or weird) and then spend a moment trying to figure it out.
You can easily measure your immune system activity by looking up at a nice blue sky. Actually to be honest, any flat area of color – even a white wall – will do if you look closely enough.
The way this works is known as Blue-field entoptic phenomenon or Scheerer’s phenomenon.
Basically, the human eye is badly ‘designed’ – the blood vessels lay across the retina rather than going behind it. This means that your eye gets to see those blood vessels – and the blood going through them.
Now those blood vessels are in a static, fixed pattern no matter where your eye looks. So like most things that don’t change, your brain basically ignores them. It just edits them out.
White blood cells on the other hand? They don’t absorb blue light all that well, and they’re pretty rare. So they do show up. Most people don’t pay attention to them, it seems. (Some can’t see them at all). For some reason, I can see them. And they’re most visible when you look at a bright blue smooth surface – for which the sky works brilliantly.
They look like white dots which move around randomly. Some people report them leaving little trails behind them. Either way, if you look closely, you should be able to see them – and that’s where it turns into a diagnostic trick.
Once you get used to looking for them, you can figure out roughly how many of them there are. This is more of a “more than normal / less than normal” measurement rather than a hard value.
As a result, I normally get a heads up whenever I’m getting a bad cold because I keep a rough track of how many white blood cells are zipping through my eyes. If I look into the sky and see something that looks like static on a TV screen, I’m going to have a bumpy ride soon.
And that’s it. Just look at the sky, and get a quick built-in health check. No mess. No fuss. Not tremendously useful, but it’s always nice to get a bit of warning.