Upper eyelid

The lower and upper eyelids are soft tissue structures which cover the base of orbits on the face and protect the eyes, when closed. The space between lower and upper eyelid is called palpebral fissure.

Both lower and upper eyelids comprise of various soft tissue structures or components. From front to back, these include the skin, loose subcutaneous tissue, skeletal muscle, orbital septum, the tarsus and conjunctival membrane:

• The looseness of connective tissue in the subcutaneous layer allows for fluid accumulation and swelling in case of injuries and infections.

• The skeletal muscle includes the palpebral part of orbicularis oculi muscle, anchored on either side by medial and lateral palpebral ligaments.

• Next, the orbital septum is an extension of periosteum which descends into the upper eyelid. Unlike the lower eyelid where it is attached to the tarsal plate, here it attaches to the tendon of levator palpebrae superioris muscle, which separates it from the superior tarsal plate below. There are numerous sebaceous tarsal glands situated within the tarsal plates. Their obstruction could lead to inflammatory swelling of the tarsal glands, called chalazion.

• Lastly, a thin conjunctival membrane underlines the posterior surface of the lower and upper eyelids and reflects onto the sclera of the eyeball at the inferior and superior conjunctival fornices.

Vasculature: Blood supply to lower and upper eyelids comes via the branches of ophthalmic artery, angular branch of facial artery, and superficial temporal artery and its transverse facial arterial branch.

Innervation: Sensory innervation of upper eyelid is via the ophthalmic division of trigeminal nerve (V1), whereas the motor innervation arises from the facial nerve. In addition, the oculomotor nerve innervates the levator plapebrae superioris muscle.