What Is the Main Cause of Dry Eye?

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Split screen showing dry eyes on the left and healthy eyes on the right

Unfortunately, the uncomfortable symptoms of dry eye are very common. Around 6 million Canadians suffer from the scratchy, gritty sensations associated with the condition. 

Fortunately, relief is available. In order for your optometrist to recommend the best dry treatment, they first need to understand what the underlying cause of your dry eye might be. 

What is the main cause of dry eye? It is not an easy question to answer. Dry eye is a complex condition with underlying causes that can be exacerbated by environmental factors, medications, ageing, and more.

Read on to learn more about dry eye and what the main cause of your symptoms might be.

What Is Dry Eye?

Dry eye is exactly what it sounds like—it occurs when there is not enough moisture to adequately lubricate your eyes and keep them comfortable. 

The condition is rarely serious on its own, but if left untreated, dry eye can cause long-term damage. Corneal scratches and tissue damage can occur as a result of dry eye.

Symptoms of Dry Eye

Symptoms of dry eye can include:

  • Stinging or burning eyes 
  • Scratchy feeling
  • Foreign body sensation
  • Fluctuating vision
  • Excessive watering
  • Stringy discharge

2 Types of Dry Eye

There are 2 main types of dry eye, and you could be suffering from either one or a combination of both! One type—aqueous deficiency—occurs when your eyes don’t produce enough tears. The other type—evaporative dry eye—happens when your tears are not of ideal quality. 

Let’s explore both types of dry eye:

Aqueous Deficiency 

Aqueous deficiency is the least common of the 2 types of dry eye. It accounts for only about 10% of all dry eye cases. 

There are several reasons why the eyes may not produce enough tears. These include:

  • Wearing contact lenses
  • The normal ageing process
  • Certain medications like antihistamines
  • Medical conditions like rheumatoid arthritis or Sjögren’s Syndrome
  • Recent laser eye surgery

Evaporative Dry Eye

The tear film plays a significant role in dry eye. It contains 3 layers that must be balanced in order to produce high-quality tears. If your tears are not of the proper composition, they may evaporate too quickly, before they have had a chance to moisten your eyes.

This type of dry eye is most common, accounting for 90% of cases.

The 3 layers of  your tear film are:

  • Mucin: The mucin, or mucus layer, spreads the tears evenly over the eye’s surface.
  • Aqueous: The aqueous, or water layer, hydrates the eye.
  • Meibum: The meibum, or oil layer, ensures the water stays on the eye and stops it from evaporating.
Layer of the tear film shown through eye

Meibomian Gland Dysfunction

Sometimes, the cause of your evaporative dry eye can stem from the meibomian glands. These tiny glands are located along both the top and bottom of your eyelids. 

The meibomian glands produce the meibum, the oil layer of your tears. If these glands are blocked, there might not be enough oil in your tear film. Without sufficient oil, water can evaporate too quickly, before it has a chance to moisten the eyes. 

Inflammation of the eyelids is known as blepharitis, and it can also interfere with the oil layer of your tears. When blepharitis is present, the inflammation can impede the meibomian glands from producing enough oil. 

At a dry eye evaluation, your optometrist will examine your meibomian glands. If the glands are clogged or otherwise not functioning well, there are treatments available. 

Diagnosing Dry Eye

There are several tests available, as well as advanced diagnostic equipment, that can help optometrists determine the cause of dry eye.

Some of these tests and tools might include:

  • Meibomian Gland Imaging: Your optometrist can get a good look at the meibomian glands in high definition to see if they are clogged.
  • Tear Osmolarity: A diagnostic test of the salt content of your tears can help determine the presence of a tear film imbalance and the severity of your dry eye disease.
  • Non-invasive Keratograph Tear Breakup Time (NIKBUT): Measuring the ​​time between the last blink and the appearance of the first dry spot in the tear film can tell your optometrist a lot about the quality of those tears.
  • Blink Pattern Analysis: There are tools available to run computer analyses of how often you blink and how thick the oil layer of your tears is between each blink.
  • Lipid Layer Thickness Tests: Your optometrist can evaluate how much meibum is actually present in your tear film.
  • Fluorescein Eye Stain Test: This test uses a special dye in the eyes to determine if the colour spreads evenly over the ocular surface.
  • Questionnaires: A variety of lifestyle and environmental factor questionnaires can be administered to help determine the cause of your dry eye.
Women looking up to apply eye drops to her dry eyes

Finding Relief

Once tests have been performed and your optometrist fully understands your eyes, symptoms, and lifestyle, the cause of dry eye can be determined. 

The particular type of dry eye you’re dealing with will guide your optometrist to the right treatment option to help you find relief. 

Some at-home treatment options your optometrist might prescribe include:

  • Prescription eye drops
  • Lubricating eye drops
  • Hot compresses
  • Omega-3 supplements
  • Eyelid cleaners
  • Blinking exercises

Remember that at-home treatments generally only address symptoms, rather than the root cause of your dry eye. For advanced cases of the disease, and for long-term relief, in-office treatments are available. 

In-office treatments might include:

If you’re dealing with dry eyes, you should book an appointment for a comprehensive eye exam today.

Written by Anita Voisin

Dr. Voisin grew up in Waterloo, Ontario, and graduated as a Doctor of Optometry from the University of Waterloo in 1997. She practiced in Oshawa, Ontario for 2 years prior to joining Trevor Miranda at Cobble Hill Eyecare (formerly Mill Bay Eyecare). In June 2000, Anita also began providing Chemainus with comprehensive ocular health examinations in our then newly opened Chemainus office. Anita strives to improve the quality of life of each of her patients and enjoys educating local organizations on the importance of eye health. She is actively involved in the community with the Chemainus Chamber of Commerce and the Rotary Club of Chemainus. Dr. Voisin is dedicated to serving the vision needs of the Cowichan Valley and welcomes new patients at either location. Dr. Voisin is available for appointments in Chemainus and Cobble Hill.
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