What Is Dry Eye?

Dry eye is a common problem that affects the tears that cover and moisten the front of the eye. It happens when the natural layer of tears that coats the front of the eye, called the tear film, breaks down. In turn, your eyes either don’t produce enough tears to lubricate them or the tears dry too quickly. 

This can make your eyes feel very uncomfortable. Common symptoms include burning, itching, or feeling like you have sand or grit in your eyes. It can also make your vision blurry.

Keep reading to learn more about dry eye symptoms, its causes, and how dry eye is diagnosed. 

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How Do Tears Work?

[Illustration/medical image that shows various parts of the eye; second image if possible showing the three layers of the tear film]

When you blink, a layer of tears called the tear film spreads over the eye. This coats your eye, protecting it from damage. It also helps smooth out tiny bumps on the surface of your eye to make your vision sharper.

The tear film has three layers. Each plays an important role. Dry eye can occur when one or more of these layers is damaged or doesn’t work properly.

• The oily layer: This is the outermost layer. Your meibomian glands produce it. This oily layer smooths the surface of your eye and keeps your tears from drying up too quickly.
  
  
• The watery layer: This is the middle layer of your tear film. The lacrimal glands in your eyelids produce it. It is the most liquid part of your tear film. It helps keep your eyes clean by washing away debris.
  
  
• The mucus layer: This is the innermost layer, closest to the surface of the eye. The conjunctiva makes it. The mucus layer helps the tears stick to the surface of the eye. Without it, your tears wash away too quickly. This leaves the eyes unprotected and prone to dryness.

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What Are the Symptoms of Dry Eye?

Symptoms include:

• Excessive tearing — this may sound odd, but oftentimes the eye responds to the dryness by overproducing tears
• Burning, stinging, or itching sensation
• Scratchy eyes or feeling like you have sand or grit in your eye
• Blurry vision (made worse when reading, using electronic screens, or driving)
• Discharge and/or your eyelashes stick together from dried discharge (usually worse upon waking)
• Frequent blinking
• Redness
• Light-sensitivity
• Eye pain and/or headache
• Heavy eyelids
• Eye fatigue and strain
• Extra dryness and discomfort if you wear contact lenses

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What Causes Dry Eye?

A variety of factors can cause dry eyes. These include:

• Environmental factors: Dust, wind, hot or dry air, prolonged screen time (we blink less when looking at screens), contact lenses, and allergies all contribute to dry eye.
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• Hormonal changes: Hormonal changes can cause us to produce fewer tears. This is particularly true for women who have experienced menopause or who are pregnant. Symptoms may improve after pregnancy once hormone levels return to normal.
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• Certain medical conditions: Inflammation of the eyelids (called blepharitis) or other inflammatory eye conditions like uveitis and iritis; thyroid eye conditions; neurological conditions such as stroke, Parkinson’s disease, Bell’s palsy, and trigeminal nerve dysfunction; Sjogren’s syndrome and other autoimmune disorders, such as lupus and rheumatoid arthritis; and diabetes can increase your risk of dry eye.
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• Medications and supplements: Certain medications can increase your risk for dry eye. These include those that treat depression and anxiety (selective serotonin reuptake inhibitors, or SSRIs), allergies (antihistamines), high blood pressure (beta-blockers and diuretics), and hormonal changes from menopause (hormone replacement therapy). Prescription and/or over-the-counter cold medicines, pain relievers, sleeping aids, and oral contraceptives can also increase your risk.
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• Eye surgery: Vision-correcting refractive surgery (LASIK or PRK) can cause dry eye. Oftentimes, this is only temporary. But for some people, these symptoms can persist.

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How Is Dry Eye Diagnosed?

Your doctor will usually ask about your medical history, conduct an eye exam, and may order tests to diagnose dry eye. Often, a variety of factors contribute to dry eyes. It’s important to understand and treat all the causes of dry eye. Otherwise, your symptoms may continue to get worse.

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Medical History

Your eye doctor will capture your full medical history. This can flag things like previous surgeries or medical conditions that may be contributing to dry eyes.

Eye Exam

Your doctor will check your face and eyes to ensure that all parts of your eye are working properly. They may also look at your blink movements and examine your tear film.

Testing

Your doctor may perform a variety of tests to measure your tears. They may also order blood tests to understand if other problems are contributing to your dry eyes.

Tests include: 

• Tear breakup time (TBUT): This test helps your doctor understand how stable your tear film is. Your doctor will put a temporary dye in your eye and then measure how quickly your tears evaporate between blinks.
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• Schirmer test: This test measures how well your eyes produce tears. Your doctor will put a thin strip of paper under your lower eyelid. Then, they’ll measure how much moisture the paper absorbs in five minutes.
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• Tear meniscus height: This test measures the height of the tears that accumulate above your bottom eyelid.
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• Blood and other tests: Your doctor may perform or order other tests, including blood tests, to see if Sjogren’s syndrome or other conditions are contributing to dry eye symptoms. 

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Learn more about treatment options for dry eye and how to manage symptoms at home.