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A group of patients comes in almost every day with dry eyes. Dry eyes are probably the most common eye disease an eye doctor will see in their office, and so today we will cover what your tear film is made of, and how people often confuse the tear film with the tear ducts.
We’re gonna go over the different layers of your tear film. We’ll start with the bottom mucus layer of your tear film. Around the surface of your eye, there are little goblet cells, and these goblet cells produce the bottom mucus layer of your tear film that’s right on the surface of your eye. Those cells are important because, for the first layer, you have to have a stable platform for the tears to rest on.
The next layer is a liquid or watery layer produced by the lacrimal gland, located beneath the lid in the outer corner of the orbit. This lacrimal gland then secretes tears into your eyes, so when you get emotionally upset or you get something in your eye, that lacrimal gland pours a lot of water, but it normally produces tears.
The outer layer of your tear film is called a lipid or oily layer, and this covers the water layer. The function of this layer is to protect the liquid part from evaporating off your eye, and obviously, oil’s a lubricant. This layer is produced by glands in your eyelid that secrete oil onto your tear film. You have a row of glands all the way across your lid, and they secrete oil into 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, so it lets the liquid layer evaporate off your eye, and therefore, that leads to dry eyes. When the liquid layer evaporates away, 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 are many risk factors for dry eyes, but that’s the culprit for the inflammation.
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 are many risk factors for dry eyes, but that’s the culprit for the inflammation.
So you have goblet cells on the surface of your eye that produce the bottom mucus layer, the lacrimal gland produces the water layer, and then the meibomian glands produce the oily layer of 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 cause 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 when you’re in a lake where there’s clear water, and there’s no wind, you can see down through into the water, but as soon as there are waves or 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 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, or look at a computer, because when you do those things, you concentrate, you blink less, and your eyes dry up more. It’s important to have a good tear film and healthy eyelids for stable, comfortable eyes.
If you have any questions about dry eyes or tear film, contact the Cataract & Refractive Institute of Florida. If not, may God grant you healthy eyes and great vision.
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