Tarsal glands, also recognized as Meibomian glands, are small yet significant components within the eye’s anatomy. These glands play a role in maintaining ocular comfort and overall eye health. Their proper functioning is necessary for the eye’s surface to remain lubricated and protected.
Anatomical Location
Tarsal glands are located within the eyelids, specifically embedded in a dense connective tissue structure called the tarsal plate. They are arranged in a linear fashion, running perpendicular to the eyelid margin. The upper eyelid typically contains a greater number of these glands, ranging from approximately 25 to 40. The lower eyelid has fewer, generally between 20 and 30 glands, with some sources indicating around 25. Their ducts open at the free margins of the eyelids, near the base of the eyelashes.
Role in Eye Health
The primary function of tarsal glands is the production of an oily substance known as meibum. This meibum forms the outermost layer, the lipid layer, of the tear film that covers the eye’s surface. The tear film itself consists of three main layers: an inner mucin layer, a middle watery (aqueous) layer, and the superficial oily layer. Meibum is essential for slowing the evaporation of the aqueous layer, which helps keep the eye consistently moist.
This oily secretion also aids in lubricating the eye’s surface, reducing friction during blinking, and ensuring smooth eye movement. A stable tear film, supported by healthy meibum, is important for clear vision and overall eye comfort. The meibum also helps to create a seal when the eyelids are closed, preventing tears from spilling onto the cheek. More than 90 different proteins have been identified in meibomian gland secretions, contributing to the complex nature of meibum.
Understanding Gland Dysfunction
When tarsal glands do not function correctly, it can lead to a common condition called Meibomian Gland Dysfunction (MGD). This dysfunction occurs when the glands become blocked or inflamed, altering the secretion of meibum. The meibum may become thicker or reduced in quantity, which impairs its ability to properly coat the tear film. This leads to increased tear evaporation and tear film instability.
Symptoms of MGD often overlap with those of dry eye syndrome and can include irritation, dryness, burning, redness, and a gritty sensation. Individuals may also experience blurred or fluctuating vision, light sensitivity, or crusty eyelids. If left unmanaged, MGD can lead to persistent discomfort and may contribute to conditions like blepharitis, an inflammation of the eyelids. Management strategies for MGD often involve at-home practices such as applying warm compresses to the eyelids to help liquefy the meibum, followed by gentle eyelid hygiene. This approach aims to improve meibum quality and facilitate its release from the glands.