The lower eyelid, tethered medially and laterally by the canthal tendons, is normally suspended at the level of the inferior limbus with the aid of orbicularis tone counterbalanced by the force of the lower eyelid retractors and gravity. The lower eyelid is apposed to the globe because of the posterior position of the canthal tendon insertions relative to the projection of the globe. Disruption of the normal anatomic relationships from trauma or inflammatory disease or as a result of surgical resection of tumors can result in a poorly functioning lower eyelid with poor cosmesis. The lower eyelid has been conceptualized as consisting of three layers or lamellae. The anterior lamella is composed of skin and orbicularis muscle; the middle lamella is composed of the lower eyelid retractor (capsulopalpebral fascia) and fat; and the posterior lamella is composed of tarsus and conjunctiva. One or more of the lamellae may be disrupted following trauma or tumor resection, and each layer must be addressed in order to reconstruct a normal-appearing and -functioning lower eyelid. Imbalance of tension at the anterior and posterior lamellae, especially in the setting of lower eyelid laxity, can result in malrotation of the eyelid margin, causing entropion or ectropion. For example, inflammation and scarring of the conjunctiva from Stevens-Johnson syndrome or ocular cicatricial pemphigoid will produce entropion, whereas contraction of vertical cutaneous scar or ichthyosis will cause ectropion. A balance of tension of the lamellae must be maintained during reconstruction of the lower eyelid in order to prevent secondary malrotation. Disruption of normal anatomy as often seen following trauma can be addressed by reapproximation of the disrupted segments to their normal anatomic positions. Only rarely will trauma to the lower eyelid result in loss of tissue. Reconstruction with local flaps or free grafts is occasionally needed in traumatic cases that present in a delayed fashion. Local flaps and free grafts are needed to fill and reconstruct a defect in the lower eyelid, a situation that most often presents following resection of tumor.
Reconstruction of facial defects with local flaps – a training model for medical students?
