Dry eye disease affects a growing amount of people around the world for several reasons.

The last 30 years have seen a rising global awareness of the disease and in recent years especially, there has been much research done on the disease. Questions such as what constitutes as ‘dry eye disease’, what causes it, who is most likely to suffer and a variety of other investigative queries have been explored.
Dry eye is a disease which is comprised of many different factors and has a multitude of possible symptoms. The symptom severity can range from a minor inconvenience to incredibly disruptive and affect daily life. The impact of dry eye can affect everything from driving and reading to your ability to work and socialize with friends.1

 

Two types of dry eye

While dry eye is a disease which is caused by a variety of factors and affects people for different reasons and in different severities, there are two main classifications of dry eye. These two classifications are not mutually exclusive, meaning a patient may suffer from one, the other, or a combination of both. The names of these classifications are aqueous deficient and evaporative.1

Aqueous deficient dry eye disease

Aqueous deficient dry eye, sometimes referred to as tear deficient dry eye, is caused when your eyes don’t naturally produce enough tears to keep your eyes properly lubricated and hydrated. The part of your body which produces tears is called the lacrimal gland. In aqueous deficient dry eye, the lacrimal gland does not generate a sufficient amount of the watery component of tears.

 

Evaporative dry eye disease

Evaporative dry eye is the most common form of dry eye disease. Aqueous deficient dry eye patients do not have enough tears whereas evaporative dry eye patients do not have the right quality of tears. Additionally, while aqueous deficient affects the lacrimal gland, evaporative dry eye is related to conditions concerning the eyelid or the surface of the eye (referred to as the ocular surface).1

Lid-related evaporative dry eye is most notably caused by Meibomian Gland Dysfunction (MGD).2

Your tears are made up of water and oil. The watery layer, produced by the lacrimal gland, keeps your eyes moist and helps keep out dirt and debris. The oil layer keeps the watery layer from evaporating and is produced by your Meibomian glands. Your Meibomian glands sit at the edges of your eyelids and every time you blink they spread it across the eye’s surface.

In MGD, the glands get blocked and cannot make enough oil to cover the eye. As a result the watery layer evaporates leading to dry eye symptoms. MGD is the most common cause of dry eye seen in both clinical and population based dry eye studies.1

 

If you are experiencing dry eye symptoms it is important to visit a doctor so he/she can accurately diagnose the classification of your specific dry eye. This will have a large impact on the success of any treatment plan implemented.

If left untreated, the various forms of dry eye disease can lead to damage to the surface of the eye (ocular surface damage), damage to the cornea and vision problems.