Dry eye

Nowadays, eye dryness or dry eye disease (also called dry eye syndrome, keratoconjunctivitis sicca, dry keratitis or xerophthalmia) is one of the most frequent opthalmology diseases (accounting for 30% of visits). In recent years, it has become more widespread and it is one of the most common eye diseases worldwide.

The tear film

In order to protect the eye surface from external aggressions, our body has a complex natural protection mechanism: the tear film.

Tears are composed mostly of water, the rest being essentially mineral salts, some enzymes, proteins, lipids, etc.

Tears perform several functions: in addition to their important moisturising and lubricating action, they maintain the adequate metabolism of the ocular surface and also have a cleansing and anti-infective action. The lachrymal glands are located over each eye, behind the outer side of the upper eyelid and are responsible for secreting tears. With each blink, the tears spread over the surface of the eye. This lubrication is essential to preventing the eyelid from damaging the cornea from rubbing, when opening and closing.

Causes of dry eye

Hyperosmolarity and tear film instability are the main mechanisms causing dry eye. There are essentially two types of dry eye:

• Dry eye due to insufficient aqueous secretion

Sjögren's syndrome is one of the best-known systemic diseases that causes this type of dry eye. It is an autoimmune disease that damages the exocrine and mucous glands, producing alterations in the tear film. The main manifestations are dry eye, dry mouth (xerostomia) and arthritis. 

Dry eye due to lack of watery secretion can also appear as a consequence of a lack of lacrimal secretion (ageing), an obstruction of the lachrymal gland duct, a blockage of the reflex or due to the consumption of systemic drugs (anti-acne, some beta-blockers, oral contraceptives, antihistamines, etc.).

• Evaporative dry eye

Some causes of intrinsic evaporative dry eye may be due to a meibomian gland dysfunction (meibomitis), blepharitis, or a low blink rate. This type of dry eye is very common in post-menopausal women due to hormonal changes.

Extrinsic evaporative dry eye is caused by disorders on the eye's surface as a consequence of the continuous use of contact lenses, eye surface diseases, allergic conjunctivitis, dry environments, excessive computer use, after refractive surgery or the chronic use of eye drops with preservatives, etc.

What are the symptoms of dry eye?

The most common clinical symptoms of dry eye are the sensation of eye dryness, grit and burning, which typically worsen throughout the day. Fibrous discharge, transient blurred vision, photophobia (sensitivity to light), discomfort when wearing contact lenses, redness, and crusting of the eyelids may also occur.

How is dry eye treated?

Some healthy habits for treating dry eye are:

• Avoid dry or very smoky environments.
• Minimise the use of air conditioning and heating.
• Use humidifiers.
• Blink frequently.
• If your work requires you to spend a long time in front of the computer, take breaks from the screen around every half hour.
• Hydrate the eye surface by using hydrating eye drops.
• Maintain good eyelid hygiene.
• Moderate the use of contact lenses.
• Protect the eyes from the influence of dehydrating agents (wind or cold) using sunglasses or lenses, etc.

If the symptoms of dry eye do not decrease after applying these measures, a visit to the ophthalmologist will be necessary.