Dry eye

Doctors use the term “dry eye” (or “keratoconjunctivitis sicca” in Latin) to refer to a group of conditions that are caused when the eyes don’t produce enough tear fluid or when the tear film over the eyes doesn’t function as normal.

A common cause is damage to or malfunctioning of the eye’s tear gland (lacrimal gland). The function of the tear gland is to keep the cornea and conjunctiva of the eye adequately moistened by producing tear fluid (lacrimal fluid). A healthy tear film over the surface of the eye contains fatty oils and serves to prevent the evaporation of tear fluid and to protect the eye from drying out due to wind, for example.

The oily secretion in the tear film is produced by sebaceous glands at the edge of the eyelid, which are known as meibomian glands. If these become blocked, the oily layer is then missing from the tear film and, as a result, more tear fluid evaporates.

If the tear glands produce too little fluid and if an adequate tear film is not spread over the eye, symptoms such as redness or burning sensations may occur, which can impair vision or lead to inflammation of the conjunctiva (conjunctivitis) or the cornea.

The likelihood of developing dry eye increases with age. Dry eye is also more common among women than men.

People who wear contact lenses often tend to have dry eye, which can be so severe in some cases that they stop wearing their lenses.

Various symptoms indicate dry eye. These include:

• red eyes
• stinging or burning sensations or a feeling of pressure in the eyes
• sharp or dull pain in one part of the eye, behind the eye or around the eye
• the sensation of having a grain of sand stuck in the eye
• a feeling of heaviness in the eyelids
• difficulty opening the eye
• blurred vision (usually temporary)
• tired eyes – especially in people who wear contact lenses
• sensitive eyes that water easily

A common cause of dry eye is failure of the tear glands to produce enough tear fluid and failure of a sufficient oily tear film to form over the eye to protect it from external influences.

This is often due to damage to the tear glands or meibomian glands, which no longer function correctly. If the tear film over the eye evaporates at a faster rate than it can be formed, this leads to dry eye.

Factors that make this process more likely to occur are:

• eyelid deformities that affect closing of the lid
• restricted blinking – for example, in people with Parkinson’s disease

In addition, using eye drops containing preservatives that are designed to reduce swelling or wearing contact lenses for long periods at a time can lead to excessive evaporation of the eye’s tear film.

Other possible causes of dry eye are:

• dry air and drafts
• air conditioning and fan heaters
• tobacco smoke
• chronic inflammatory conditions, such as conditions of the salivary and tear glands, thyroid gland or joints
• inflammatory diseases of the cornea and conjunctiva
• eye surgery
• taking medication that inhibits the formation of tear fluid
• working long hours at a computer and excessive use of digital media: staring at a screen for hours results in less blinking, so that the tear film is not spread adequately over the surface of the eye

Some medication can intensify the symptoms of dry eye. These include:

• diuretic medication to promote urine production
• medication to treat allergies (anti-histamines)
• medication to treat depression (anti-depressants)
• retinoids: vitamin-A-like substances, which are used to treat acne, for example

Very severe dry eye can lead to diseases of the cornea, such as corneal inflammation (keratitis) or a corneal ulcer. Scars may also form on the cornea, which can lead to vision loss.

There are a number of preventive measures that can be taken every day by people who tend to suffer with dry eye.

For example, it makes sense for people to set up their living space in such a way that seating and beds aren’t directly beside fans, air conditioners or fan heaters.

Containers of water can also be placed on radiators to humidify the air – especially during the colder months when central heating is on a lot of the time and the indoor air becomes drier as a result.

Tobacco smoke also increases the risk of dry eye. For this reason, it’s advisable to avoid smoking and passive smoking.

It’s important to remember to blink frequently when reading or using mobile devices such as mobile phones. This helps ensure that the eye is adequately protected with a tear film.

A detailed consultation with a doctor is necessary to diagnose dry eye. The doctor will ask, for example, whether the individual:

• sits close to fans or air conditioners on a daily basis
• spends a lot of time reading or on a computer
• has a pre-existing condition or takes medication that increases the risk of developing dry eye

Doctors may also use a special questionnaire for diagnosis. This can also be used to determine whether the condition is at an advanced stage and the extent to which treatment is proving effective.

If lubricating eye drops (artificial tears) help to relieve symptoms, this is another indication of dry eye.

There are also various tests that doctors can use to:

• determine the level of tear fluid
• detect minor damage to the cornea, conjunctiva or eyelid
• measure the salt content of the tear fluid – levels below a certain threshold indicate dry eye
• determine how often a person blinks – this can also indicate dry eye

Diagnostic techniques, such as meibography, can be used to investigate the functioning of the tear glands. Meibography involves illuminating the eyelids with a special light to detect possible blockages.

The treatment of dry eye depends on its severity. Treatment measures focus on relieving symptoms.

Relief is usually provided in the form of artificial tears (lubricating eye drops). If the eye is inflamed, anti-inflammatory corticosteroids for external use can help.

In many cases, making lifestyle changes is sufficient to treat dry eye. These include, for example:

• spending less time on digital media
• avoiding dry air and direct drafts
• humidifying the air in indoor spaces
• avoiding smoking and spending time in smoky rooms

People who wear contact lenses should also avoid wearing them for too long at a time.

If the patient has an illness that increases the risk of dry eye, this pre-existing illness must be treated first.

Surgery may be considered in the case of eyelid deformities. For example, a drooping eyelid can be corrected with an eyelid lift (blepharoplasty).

If dry eye is caused by taking certain medication, this should be discontinued where possible and alternative medication sought – in consultation with a doctor. If this isn’t possible, it may be helpful to use lubricating eye drops without preservatives on a permanent basis.