Hello! I’m Dr. Croley and welcome to Case of the Day. Today we’re gonna discuss a group of patients who come in almost everyday with dry eyes. Dry eyes is probably the most common eye disease an eye doctor see in their office. I thought I would cover what is composed, what are your eyes or your tear film, what is it made of; and what comprises your tear film, so we’re gonna go over that. And try to also clear up, people are always confused about “my tear ducts are not working well” and they confuse that with actually the glands that produce the tears. People think the ducts actually produce the tears, when it’s not the case.
So we’re gonna cover the different layers of your tear film. So we’re gonna start with the bottom mucus layer of your tear film, which is around the surface of your eye, there’s little goblet cells, and these goblet cells produce the mucus bottom layer of your tear film, that’s right on the surface of your eye. Those cells are important because that first layer you’ve got to have a stable platform for your tears to rest on.
And then the next layer, is a liquid or water layer that’s produced by the lacrimal gland that’s up here, underneath the lid, up here on the outer corner of the orbit. This lacrimal gland that secretes tears in your eyes and so when you get emotionally upset or you get something in your eye, then that lacrimal gland pours a lot of water, but it normally produces tears that’s sort of a steady flow for the liquid layer of your tear film.
Then the outer layer of your tear film is called a lipid or oily layer and that lipid or oily layer covers over the water layer. The purpose or the function of the oily layer is to protect the liquid part from evaporating off your eye, and obviously, oil is a lubricant. That layer is important, as well.
That layer is produced by glands in your eyelid that secrete oil onto your tear film. So I hope this will show up, but I wanna hold and you can see the little glands that are in the lid this machine takes image, sort of a 3D image of the glands when we flip your lid inside out, so we can see the glands. And so you have a row of glands all the way across your lid and they secrete oil onto your tear film and those are called Meibomian glands.
Meibomian gland disease or dysfunction is the most common cause of dry eyes. That is, the oily layer is not sufficient. It lets the liquid layer evaporate off your eye and therefore, it leads to dry eyes. So then when the liquid layer evaporates away then the minerals of your body and in your tear film then become concentrated. So the salt level in your tear film becomes elevated. Salt causes inflammation so now that just makes things get worse and the glands and cells get even sicker. Just like there’s no fish that live in the dead sea because the salt concentration is too high, many people with dry eyes have these salt levels very high, and that causes inflammation, which when you listen to the TV commercial about Restasis, it says “dry eyes due to chronic inflammation.” So inflammation due to elevated salt levels is sort of the bottom line culprit of what causes dry eyes. There’s many risk factors for dry eyes, but that’s the culprit for the inflammation.
So you have the goblets cells on the surface of your eye that produce the bottom mucus layer; the lacrimal gland that produces the water layer; and then the Meibomian glands that produce the oily layer or your tear film. You have to have all three of those layers in the right proportions for your tear film to be stable. And for your vision to be clear, that’s the first thing that light hits to be focused into your retina is how smooth is the tear film covering over your cornea. Just like if you’re in a lake where there’s clear water and no there’s wind, you can see down through into the water. But as soon as there are waves and ripples in the lake, then you don’t see as well. It’s the same thing with your vision. That tear film has to be smooth across your cornea. So this goes across your cornea, there’s a smooth tear film, so when light focuses through to your retina, it is a smooth surface and it gives you clear vision.
Commonly, people who have dry eyes have intermittent blurred vision and they have more trouble with blurred vision when they read, watch TV, look at the computer, those kind of things because when you do those things you concentrate, you blink less, your eye dries up more. We now have young kids coming in with dry eyes; a 12-year old girl we handled about a month ago and all they’re doing is gaming all day long. And so they’re not gonna blink, they’re not gonna miss one laser blast, and now they’re getting dry eyes.
So it’s important to have a good tear film, healthy eyelids and all three layers of your tear film are important for you to have a nice tear film and stable, comfortable eyes.
So if you have any questions about dry eyes, or tear film, or any of that kind of thing, please contact us through the website. If not, may God grant you healthy eyes and great vision.