What Is Dry Eye?
How Do Tears Work?
When you blink, a film of tears spreads over the eye. This keeps the eye’s surface smooth and clear. The tear film is important for good vision.
The tear film is made of three layers:
- An oily layer
- A watery layer
- A mucus layer
Each layer of the tear film serves a purpose.
The oily layer is the outside of the tear film. It makes the tear surface smooth and keeps tears from drying up too quickly. This layer is made in the eye’s meibomian glands.
The watery layer is the middle of the tear film. It makes up most of what we see as tears. This layer cleans the eye, washing away particles that do not belong in the eye. This layer comes from the lacrimal glands in the eyelids.
The mucus layer is the inner layer of the tear film. This helps spread the watery layer over the eye’s surface, keeping it moist. Without mucus, tears would not stick to the eye. Mucus is made in the conjunctiva. This is the clear tissue covering the white of your eye and inside your eyelids.
Normally, our eyes constantly make tears to stay moist. If our eyes are irritated, or we cry, our eyes make a lot of tears. But, sometimes the eyes don’t make enough tears or something affects one or more layers of the tear film. In those cases, we end up with dry eyes.
Dry Eye Symptoms
Here are some of the symptoms of dry eye.
- You feel like your eyes are stinging and burning.
- Blurred vision, especially when reading
- There is a scratchy or gritty feeling like something is in your eye.
- There are strings of mucus in or around your eyes.
- Your eyes are red or irritated. This is especially true when you are in the wind or near cigarette smoke.
- It is painful to wear contact lenses.
- You have lots of tears in your eyes.
Having a lot of tears in your eyes with dry eye might sound odd. But your eyes make more tears when they are irritated by dry eye.
Dry Eye Causes
People tend to make fewer tears as they get older due to hormonal changes. Both men and women can get dry eye. However, it is more common in women—especially those who have gone through menopause.
Here are some other causes of dry eye.
- Certain diseases, such as rheumatoid arthritis, Sjögren’s syndrome, thyroid disease, and lupus
- Blepharitis (when eyelids are swollen or red)
- Entropion (when eyelids turn in); ectropion (eyelids turn outward)
- Being in smoke, wind or a very dry climate
- Looking at a computer screen for a long time, reading and other activities that reduce blinking
- Using contact lenses for a long time
- Having refractive eye surgery, such as LASIK
- Taking certain medicines, such as:
- Diuretics (water pills) for high blood pressure
- Beta-blockers, for heart problems or high blood pressure
- Allergy and cold medicines (antihistamines)
- Sleeping pills
- Anxiety and antidepressant medicines
- Heartburn medicines
Tell your ophthalmologist about all the prescription and non-prescription medicines you take.