Dry eyes occur when tears are unable to provide sufficient moisture for the eyes. The reason for this may be insufficient production of tears or production of poor-quality tears.
Dry eyes feel uncomfortable or they may sting or burn. Dry eyes may occur in certain circumstances such as on an airplane, after an extended use of a computer, while riding a bike or in an air-conditioned room.
Treatment for dry eyes includes lifestyle changes and eye drops and aim to relieve symptoms and ease discomfort. More severe cases of dry eyes may require surgery.
Symptoms for dry eyes, which usually affect both eyes, include:
- A stinging, burning or scratchy sensation in the eyes
- Stringy mucus in or around the eyes
- Increased eye irritation from smoke or wind
- Eye fatigue
- Sensitivity to light
- Eye redness
- Difficulty wearing contact lenses
- Periods of excessive tearing
- A sensation of having something in the eyes
- Blurred vision that often worsens after focusing for a prolonged period
Dry eyes are caused by lack of tears or poor-quality tears. Tears are a complex mixture of water, fatty oils and mucus. This combination makes the surface of the eyes smooth and clear and it protects the eyes from infection.
In some cases, an imbalance in the composition of tears is the cause of dry eyes. In other cases, people don’t produce sufficient tears to keep the eyes adequately lubricated. Eyelid problems, medications or environmental causes can also lead to dry eyes.
Problems with the composition of tears, oil, water and mucus, can cause dry eyes symptoms.
- Oil: If the oil glands (meibomian glands) don’t produce enough oil, the watery layer evaporates too quickly leading to dry eyes. Meibomian dysfunction is more common in people with inflammation along the edge of the eyelids, rosacea or other skin disorders.
- Water: tear glands produce the watery layer (lacrimal glands). It cleanses the eyes and washes away foreign particles or irritants. Insufficient amounts of water can cause the oil and mucous layers to touch and lead to a stringy discharge.
- Mucus: The mucus layer spreads the tears evenly over the eye surface. Insufficient mucus can lead to dry spots to form on the front surface of the eye (cornea).
Decreased tear production
Decreased tear production or otherwise known as keratoconjunctivitis sicca can lead to dry eyes. The causes of insufficient tear production include:
- Age: tear production diminishes with increasing age. Dry eyes are common in people over 50.
- Postmenopause: women after menopause may have a decreased production of tears due to hormonal changes.
- Medical condition that reduces tear production: diabetes, rheumatoid arthritis, scleroderma, lupus, Sjorgen’s syndrome, thyroid disorders and vitamin A deficiency are associated with dry eyes.
- Laser eye surgery: refractive eye surgeries may cause decreased tear production and dry eyes.
- Tear gland damage: inflammation or radiation can damage the tear glands and hinder tear production.
Eyelid problems that cause difficulties to blink may lead to inadequate spreading of the tears across the eye or the tears may evaporate too quickly leading to dry eyes.
Medications that cause dry eyes
- Certain drugs used to treat high blood pressure
- Antihistamines and decongestants
- Hormone replacement therapy
- Certain antidepressants
- Isotretinoin-type drugs for acne treatment
Other causes of dry eyes
- Dry air
- Tasks that require prolonged concentration such as driving, reading or working on a computer
Factors that increase the risk of dry eyes include:
- Increasing age
- Being female
- Medications that can cause dry eyes
- Laser eye surgery
- Radiation therapy aimed at the eyes
- A diet that is low in vitamin A
Possible complications of dry eyes include:
- Frequent eye infections due to inadequate tears
- Scarring on the surface of the eyes due to untreated, severe dry eyes
- Decreased quality of life due to difficulties performing daily activities
The following tips may help prevent dry eyes:
- Avoiding air blowing in the eyes
- Adding moisture to the air
- Wraparound glasses or eyeglass shields to protect the eyes
- Eye breaks during long tasks
- Adapting the eyes to the environment
- Computer screen should be positioned below eye level
- Avoiding smoke or quit smoking