Until recently, it was widely believed that lack of tear production was the main reason that people suffer from dry eyes.
Recent research indicates that in the majority of dry eye cases it is a lack of secretion of Meibum that is the problem. It is estimated that 60 to 80% of dry eye patients have Meibomian gland dysfunction (referred to as "MGD".)
What is Meibomian gland dysfunction?
The Meibomian glands are located along the eyelid margins behind the base of the eyelashes.
There are about 25 to 40 meibomian glands in the upper eyelid and 20 to 30 in the lower eyelid. Every time you blink, the glands release an oily substance called Meibum that helps tears last for a longer amount of time on the eye’s surface. These oils are responsible for helping your eyes have healthy tears in order to stay comfortably moist and free of debris.
When your meibomian glands are unable to make enough of these oils or when the oils produced are poor in quality, you can develop MGD.
If you have MGD, you are usually able to make enough tears, but your tears break down more quickly. This can result in redness, irritation, dryness, a gritty sensation or itchiness.
The operation of the Meibomian gland is thought to be controlled by hormones. It is also linked with posterior blepharitis, so if you suffer from blepharitis, you are also likely to develop dry eye syndrome.
The effectiveness of the glands also reduces with age, leading to an increase in dry eye symptoms. Other factors that cause you to suffer from MGD include the side effects of some medication, contact lens wear, and skin diseases such as acne rosacea.
Why can MGD cause watery eyes?
When these glands don't function properly, known as Meibomian gland dysfunction (MGD), it can result in dry patches on your eyes. These become sore, and extra tears are produced as a reflex.
How can MGD be treated?
Meibomian gland dysfunction can be managed.
Self help measures include: