November 10, 2013
Some of you already figured out what I mean by onions, wind, yawing and emotion. All of them can create tears in our eyes along with other things that can get in our eyes like little foreign “bodies” (allergens). Interestingly, contact lenses don’t seem to be one of those things that makes our eyes tear (for most people) even though that’s foreign. The complaint with some people and contact lenses is they can make the eye feel drier.
I did an earlier post about the top layer of tears, the oily layer. When our eyes tear however, what we get is the aqueous layer which is what most of our normal tears are made of…watery consistency. That aqueous stuff comes out of these little glands that are just behind the top of our eyeballs and a little to the temporal side. See the picture below for where those lacrimal glands are located. And by the way, the medical term for tearing is lacrimation which for some strange reason made me think of the medical term, micturition, which is what happens when I drink a lot of coffee. And by the way, coffee, being a diuretic, can have some effect on whether our eyes do have sufficient tears to keep them from feeling dry.
Not long ago I had a patient tell me they yawn when they feel their eyes were dry. I had never thought about that as being a way to help with dry eye before. So I looked that up and found on one site that someone doing that exact same thing started complaining of aching in their jaw muscles. Apparently this person yawned very frequently during the day. The connection between yawing and tearing is probably the extra pressure from facial muscles forcing tears out of the lacrimal glands. There’s an interesting condition that’s related to tearing only by the result which is called jaw-wink reflex (Marcus Gunn jaw winking) and crocodile tears (Bogorad’s syndrome). I won’t go into those except to say that it’s an extra nerve connection that’s unusual.
So onions…as you probably know…release something that causes our eyes to tear. It’s a combination of reactions that leads to the final production of what’s called, syn-propanethial-S-oxide (lacrimal factor). Our cornea, the outmost part of our eye has a lot of nerves and this chemical activates those nerves leading to the lacrimal gland making us tear. If you don’t cut that onion (or break up the cells that make the onion and release the lacrimal factor) you won’t tear. There are a lot of ways to reduce tearing from cutting an onion (use a sharper knife, cut a cold onion and others) but I suppose that’s one way to see if your lacrimal gland is working well. There is a tearless onion but because it’s genetically modified, it’s not FDA approved.
Wind…that just causes quicker evaporation than normal so those little nerves in the cornea become more active in sending that signal to start creating tears, in volume. Just thinking here, I wonder if you’re eyes feel dry if it would help by sticking your head out of the car sometimes. I’m not suggestion this to patients (especially if you’re the driver) but it’s a thought that crossed my mind. But I have suggested using a local humidifier which will create more moisture in the air.
Emotions can certainly make the eyes cry, and again, in large volume sometimes. Crying from emotions is an interesting result that doesn’t come from something physically acting in the eye. Crying from laughing (maybe I should have said, tearing from laughing) probably has to do with physically forcing the lacrimal gland to release tears. Goes to show you though that emotions can easily affect how our bodies respond, and quickly too. Nerve impulses can travel up to 100 m/s which is about a third of the speed of sound.
What if you have dry eyes? The aqueous tears that are produced by the lacrimal gland probably aren’t enough to help many people so crying over that isn’t going to help all that much. Besides the typical artificial tears you can buy at the store there are a few others that I want to mention. Maybe I’ll do another post about them another time but here are a couple of prescription supplements: FreshKote® and autologous serum drops. You’ll have to visit a doctor that can prescribe those for you. Serum drops are very interesting because they are made from your own blood.