Did You Know?
Many people think tears come from our “tear ducts” but they actually come from three different areas of the eyes and then drain through to our nasolacrimal duct also known as our tear duct.
Sometimes our eyes do not produce enough tears or the appropriate quality of tears (see tear film below) to keep them healthy and comfortable, putting us at risk for chronic dry eye disease. Other risk factors for dry eyes include:
Since there is no permanent cure for chronic dry eye disease, prevention through lifestyle modifications and regular eye exams can aid your defense against dry eyes.
Tears evaporate like any other liquid. You can take steps to prevent evaporation:
In the past, doctors thought dry eye was caused by not making enough tears. Today, we know it’s not just tear quantity, but also tear quality.
Healthy tears help lubricate, heal, and protect the surface of the eye. When your tears are not the right composition, dry eye occurs and affects your vision, causing irritation and inflammation, and increasing the risk of an eye infection.
Our tears are not just saline. Three layers comprise our tears, which contain enzymes, lipids, metabolites, and electrolytes to nourish our eyes. A healthy tear film spreads across the eye when we blink, ensuring the surface of the eye is smooth and clear. Without an adequate tear film, sharp vision is not possible.
Mucus Layer: This layer, in direct contact with the cornea, helps “adhere” the whole tear to the surface of your eye, allowing the water layer to spread evenly over the surface of the eye, keeping it moist. This layer is produced by the conjunctiva.
Water Layer: The water layer, the thickest layer, cleanses and hydrates the eye, washing away foreign particles or irritants to protect the cornea. This layer is produced by the lacrimal gland.
Oil Layer: The oil layer forms the outermost surface of the tear film, smoothing the tear surface and reducing evaporation of tears. This layer is produced by the meibomian glands.
You’ve learned about three layers of a tear, if you are as fascinated as we are about this intricate function of the eye, click here to learn more about the three types of tears our eyes produce.
The tear drainage system is an intricate system that drains our natural tears into the puncta, through the canaliculi, and into the nasolacrimal duct or “tear duct”.
Terms To Know
- nasolacrimal duct: The tear duct where tears drain through the nasal cavity and into the back of the nose (sometimes causing your nose to run when you cry).
- canaliculi: Drain channels for tears to drain from the puncta to the nasolacrimal duct.
- puncta: The “drains” located inside the upper and lower eyelid near the nose where tears drain from the eyes.
It may seem odd, but a common symptom of dry eyes is excessive tearing or watery eyes. When our eyes are irritated, they react by producing more tears to help alleviate the irritation. However, this doesn’t mean they are producing quality tears. Other symptoms that characterize chronic dry eye disease include:
A comprehensive eye exam may include the following tests to detect chronic dry eye disease:
Slit Lamp Exam: By using an intense light, a slip lamp allows your eye doctor to closely examine the surface of your eye for signs of dryness.
Eyedrop Dyes: Eyedrops containing dye allow your doctor to assess the surface condition of your eyes and determine how long it takes for your tears to evaporate.
Schirmer Test: This test uses special blotting strips to measure how much moisture the strip absorbs and determine if your tear production is sufficient.
Artificial tears can be purchased over-the-counter as a substitute for your own natural tears, offering temporary relief from dry eyes. Various options are available and can be a little overwhelming when standing in the store aisle:
Preservative or Preservative-Free Drops: If using artificial tears more than six times a day, drops with preservatives can add to the irritation. When using drops frequently or post-surgically, we recommend preservative-free drops. They come in vials and are good for 12 hours after you open them. When using artificial tears less than six times a day, a bottle drop is okay to use until the expiration date on the bottle.
Drops vs Gels: Some drops have a higher “viscosity” meaning they are a thicker drop and stay on the surface of the eye longer. These drops and gels may lubricate the eye better but have the side effect of blurriness and, therefore, may be better for nighttime use.
Although dry eye can cause redness, we do not recommend eye drops that promote reducing redness, such as Visine, as these drops can cause added irritation with prolonged use.
Your doctor may use prescription drops to treat your chronic dry eyes. You may need to use a steroid drop initially to gain quick relief. Drops such as Restasis and Xiidra help reduce inflammation and help your eyes to naturally produce more tears.
Studies have shown that nutrient-rich diets, including omega-3 fatty acids, not only benefit your overall health but also your eye health. Omega-3 oils improve function in the meibomian glands, which produce the oily layer of the tear film. Your doctor may recommend a dietary supplement, such as fish oil, to treat your chronic dry eye disease.
The drainage system in our eyes allows our tears to drain out of the eyes through the puncta. If your eyes are not producing enough tears, your doctor may insert punctal plugs to close off the puncta, allowing your natural tears to stay in the eye longer.
Basal tears are the tears we constantly produce and the type of tears detailed in the information above. Basal tears have three layers: mucus, water, and oil. The purpose of these tears is to serve as a shield protecting the eye from dirt, debris, and infection. They also nourish and lubricate the cornea so our eyes are comfortable and we can see clearly. We often do not think about basal tears being produced. (Well, until we experience dry eye!)
Reflex tears actually contain antibodies to help fight bacteria. Our eyes release large amounts of reflex tears when our eyes are irritated and we need to wash away harmful irritants or foreign bodies that may make it into our eyes. For example, this is why your eyes water when cutting an onion. The fumes from the onion irritate our eyes, triggering reflex tears.
Emotional tears are likely what you think of as tears. Sad movies, difficult goodbyes, and hard breakups all trigger emotional tears. Often, so many tears are produced that they spill out of our eyes, also known as…, you guessed it, “crying!” Since the tears drain into the puncta through to the nasolacrimal duct in our nasal cavity, our nose tends to run as well. Some research shows crying can sometimes calm us because these tears release stress hormones.
This adorable video by TED-Ed Lessons Worth Sharing sums up the What, How, and Why of our three types of tears.
