September 28, 2013
Isn’t it interesting that oil floats? But, if you recall the Deepwater Horizon spill there were large amounts of oil that didn’t make it to the surface. No floating from that oil. That was due to the large amount of dispersants added to the oil and changed how the oil behaves in salt water. Ordinarily oil is less dense and rises to the top of the water and thus it floats. You also might think oil weighs more than water because it seems so thick but it doesn’t (generally speaking). Water molecules like each other a lot…they are like little magnets…polar molecules. That’s what makes water more dense. They cling to each other tightly….best buddies (some bugs can walk on water because of that). Oil molecules aren’t little magnets so they don’t hold tight to each other even though oil seems thick. Not trying to get too technical but there are only 2 hydrogens and 1 oxygen in a water molecule. Oil molecules can be long connected chains of carbon and hydrogen making it a thick goo (more viscous).
But did you know we have oil in our eye? Yes, we do. It’s called the lipid layer but it’s just an oily substance that floats on top of our tear film, or, let’s just make it easier and say the lipid layer is the top layer of the tears that are coating our eyes. We do need those tears and we do need that top lipid layer. Dry eyes that burn and are scratchy are not comfortable.
The lipid layer is interesting. We know it’s there. Smart people found it. It comes out of these glands that are called meibomian glands. It’s a cool system how this works. You might recall the saying, “pouring oil on troubled waters.” The watery part of our tears are not really troubled but they might be if the oil, the lipid layer, wasn’t there…or wasn’t in tip top shape. If oil is on a surface of water you can usually see it because of it’s interesting interference properties with different wavelengths of light. Not so much on the eye but it’s there. Watch the youtube video below and you’ll see the calming effect that oil has on water. Very interesting. Keeps our tears nice and smooth.
Well, what else can I tell you about this lipid layer on the tears? It sometimes isn’t effective. Glands are clogged up. Yes, those little glands (my-bo-me-an) that are just on the inside of the eyelashes can clog up so there’s less coming out. That might make you think a little drop of oil on the eye will replenish that stuff. Not a good idea unless you have a bottle of your own meibomian juice around the house and then a drop would be way too much. Solving this problem is usually best by making the glands work better but there are all kinds of palliative treatments like artificial tears that can help dry eyes.
Bottom line, oil on water is a good thing when we’re talking about the eye. It does have a calming protective effect. Treating that layer might solve your dry eye.