Meibomian glands

Meibomian glands are specialised sebaceous glands located in your upper and lower eyelids, just behind the eyelashes. You have around 25 to 40 in your upper eyelid and 20 to 30 in your lower eyelid. They are named after the German doctor Heinrich Meibom, who described them in the 17th century.

These glands produce meibum, an oily mixture of lipids (fats). Every time you blink, a small amount of this oil is released onto the edge of your eyelid, where it spreads across the watery part of your tear film. This oil layer forms the outermost layer of your tear film and has an important function: it slows down the evaporation of the watery part underneath.

The opening of each Meibomian gland is located at the edge of your eyelid, just behind the eyelashes. If you look closely in the mirror, you can sometimes see small, pale dots along the edge of your eyelid; these are the openings of these glands. The glands themselves run vertically through your eyelid like tiny tubes.

The composition and quantity of meibum produced by the glands can vary from person to person. Factors such as age, hormones, medication, skin type and environmental factors all play a role. The glands may also become less effective if the opening becomes blocked or if the meibum becomes thicker than normal.

Role in the tear film

The oil layer produced by the Meibomian glands is one of the three layers of your tear film. The bottom layer is a mucous layer that adheres to the cornea, the middle layer is the aqueous layer containing nutrients and oxygen, and the top layer is the oil layer produced by the Meibomian glands. Without that oil layer, the aqueous layer would evaporate much more quickly, particularly in windy conditions, in the heat or during prolonged screen use.

Blocked or impaired function

Sometimes the openings of the Meibomian glands can become blocked by thickened meibum, skin flakes or inflammatory reactions. The composition of the meibum can also change, making it thicker and less fluid. This can lead to a reduced oil layer on the tear film, which contributes to faster evaporation of tears and a feeling of dryness or irritation.

Eyelid hygiene

Keeping the eyelid margins clean can help to keep the gland openings clear. This is usually done by gently cleaning the eyelid margins with lukewarm water or special eyelid cleansing wipes, and sometimes by applying warm compresses to the closed eyelids. The warmth can help keep the meibum fluid. If you suffer from recurring symptoms or are unsure about the best course of action, please discuss this with your optician, optometrist or ophthalmologist.

Contact lenses and Meibomian glands

If you wear contact lenses and your Meibomian glands are not functioning properly, this can affect your comfort whilst wearing them. This is because the oil film also helps to keep the lens stable and comfortable on your eye. If oil production is reduced, the lens may dry out more quickly or not stay in place as well. If you’re experiencing this, have it checked by your optician or optometrist.