The Eyelids

The free margin of each lid is about 2mm broad and has an anterior (front) and a posterior (rear) border. The eyelashes grow from the anterior border and are hairs arranged in two or three rows. The upper eyelid lashes are longer and more numerous than the lower, and they tend to curl upward. The lashes are longest and most curled in childhood. The posterior border of the lid margin tightly sits against the front surface of the globe of the eye (Fig. 3).

Visible on the margins of both lids are the tiny openings of the sweat and oil secreting glands. The largest oil-secreting glands are embedded in the posterior connective tissue substance of the lids (called the tarsus), and are called the meibomian glands. On the medial aspect of the lower lid where the lashes cease is a small papilla or mound. At the apex of this papilla is a tiny opening called the punctum. The punctum leads, by means of a small canal, through the lower lid to the lacrimal sac, which eventually drains into the nose. Tears are carried to the punctum by the pumping action of the lids. A similar but smaller opening is found in the upper lid almost directly above it.

The muscle underlying the eyelid skin is the orbicularis oculi, which is roughly circular. When it contracts it closes the eye.

(Fig. 3)