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What is Tear Osmolarity & How Does it Diagnose Dry Eye?

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Dry eye syndrome is an eye condition that affects millions of people across North America. According to studies, it’s suggested that nearly 6 million people have dry eye syndrome in Canada alone. Because of its prevalence, our team has adopted a range of dry eye diagnostic tools and treatments.

One of the ways our team evaluates dry eye syndrome in our patients is by assessing the tear film’s osmolarity. But what is tear osmolarity? And how does it affect the tear film? Today, we’re going to jump into the world of dry eye syndrome to help you understand the importance of your tear film and how we can help diagnose and manage dry eye symptoms.

Understanding the Tear Film

Before we dive into how to treat dry eyes, it’s important to first understand the role your tear film plays in your eye comfort. 

Your tear film covers the entire surface of your eye and is made up of 3 distinct layers:

Mucus Layer

The mucus, or mucin, layer is the innermost layer of your tear film, which helps fasten the other two layers to the surface of the eye. This layer, along with the water layer, makes up the bulk of your tear film, and is secreted to the surface of your eye with the help of goblet cells in the epithelium conjunctiva.

Water Layer

The water, or aqueous layer, is the thickest layer of the tear film and occupies the space between the mucus and oil layer. Produced by lacrimal glands, this layer helps keep your eye hydrated and clear from foreign bodies, like bacteria and dust. 

Oil Layer

The oil, or lipid, layer is the thinnest and lies on the outermost layer of the tear film. Lipids are produced by meibomian glands located all around the eye and are responsible for “sealing in” the rest of the tear film.

What Can Cause Dry Eyes?

Now that we understand the tear film, it’s time to understand what causes dry eyes. For the most part, dry eye syndrome develops when there is an imbalance of tear film ingredients. These imbalances can be broken down into 2 groups: aqueous tear deficiency and evaporative dry eye.

Aqueous tear deficiency occurs when your tear film’s water content is imbalanced, making it hard for your eye to stay hydrated. Evaporative dry eye occurs when oil-producing meibomian glands are inflamed or infected, which affects the quality of your oil layer and evaporates the tear film at a faster rate.

Multiple issues can cause this, including:

Woman putting eye drops in her eye to help with dry eye symptoms

What is Osmolarity?

Assessing your tear osmolarity helps your optometrist determine if your tear film has the right concentration of solutes to keep your eyes feeling hydrated and comfortable. Tear osmolarity assessments are widely used and often help optometrists determine how severe your dry eye may be and if your eyes respond to treatments.

Increased osmolarity, or hyperosmolarity, indicates a decreased production of the water and oil layers of the tear film. This is a common indicator of dry eye and is one of the symptoms that accompanies it, including redness, irritation, and even ocular surface damage.

How We Diagnose Dry Eye

Depending on what we discover while assessing your dry eye symptoms, we offer a range of different treatments. However, before we start treating you, we need to take a look at what your eyes need. We diagnose dry eyes with various cutting edge tools, including:


InflammaDry is a diagnostic tool for dry eye that helps your optometrist detect higher matrix metalloproteinase 9 (MMP-9). MMP-9 is an important enzyme found in your body that helps the healing process and bone development. However, it has been found to play a role in various illnesses like arthritis, heart disease, and even cancer.

Hyperosmolarity can trigger the development of MMP-9 in corneal epithelial cells, leading to the cycle of inflammation in dry eye syndrome.

InflammaDry uses a soft sampling fleece along your palpebral conjunctiva, a clear membrane located inside your lower eyelid. Your optometrist will be able to determine your MMP-9 levels in just a few minutes!

TearLab Osmolarity

The TearLab Osmolarity test is an easy and safe way to measure your tear osmolarity accurately in just a few minutes! Your optometrist will gently place the osmolarity test card of the test pen on the edge of your eyelid. This will collect tear fluid that will be assessed using the TearLab Osmolarity System.

Get the Right Help For Your Dry Eyes Today

Okotoks Eyecare is proud to provide you with the dry eye solutions you need. Assessing your tear films osmolarity is one diagnostic tool we use to evaluate your dry eye. Some other dry eye tests your optometrist might recommend include:

  • Interferometry, which measures the lipid layer thickness of the tear film.
  • Tear meniscus measurement, which measures the relative amount of aqueous fluid in the tear film.
  • Non-invasive tear break up time, which objectively measures the stability of the tear film.
  • Meibography, which allows us to look at the structure of the meibomian glands to see if there is blockage or atrophy.
  • Magnification, which gives us a close look at the cornea, conjunctiva, and eyelids.

Once your optometrist has determined the cause of your dry eye, theyll be able to recommend the right treatment for you. If youre struggling with dry eyes, book an appointment with our team today!

Written by Dr. Asim Prasad

Dr. Asim Prasad is a native Calgarian who earned his Bachelorís of Science degree in Vision Science and Doctor of Optometry degree from Nova Southeastern University in Ft. Lauderdale, Florida in 2008. Before becoming an optometrist, Dr. Prasad earned a bachelorís degree in Environmental Science from the University of Alberta. After working in the environmental science industry for a short time, Dr. Prasad decided to pursue his true passion: optometry.
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