Fig. 2.1 Diagrammatic view of the structures of the normal eyelid. The orbicularis muscle can be divided into the pretarsal, the preseptal and orbital parts although these are not separate anatomically. The pretarsal and preseptal parts together form the palpebral section of the orbicularis muscle which is responsible for blinking and facilitates the drainage of tears (see Ch. 20) and the orbital part is responsible for forced lid closure. The grey line is where orbicularis oculi meets the lid margin. This visible line lies anterior to the meibomian gland orifices and posterior to the eyelashes. It is the plane at which the anterior and posterior lamella can be separated during surgery. Removal of the orbicularis muscle exposes the underlying tarsal plates and orbital septum. The levator aponeurosis is the tendon of the levator muscle which inserts between the orbicularis muscle bundles and is responsible for the eyelid skin crease.

Fig. 2.2 The pre-aponeurotic fat pad lies behind the orbital septum. If it is elevated, the levator palpebrae superioris muscle with its aponeurosis is seen. Whitnall’s ligament (the superior suspensory ligament of the globe) is a thickening in the aponeurosis that helps to support the aponeurosis and the upper lid retractors. It runs from the periosteum of the lacrimal gland fossa to the trochlea of the superior oblique muscle. The inferior aponeurosis is the forward extension of the connective tissue from Lockwood’s ligament (the inferior suspensory ligament of the globe) and is continuous posteriorly with the sheath around the inferior rectus muscle (see Fig. 2.5).

Fig. 2.3 The upper lid structures can be compared in diagrammatic and histological vertical sections. The levator palpebrae superioris muscle inserts into the anterior lamella and the posterior lamella (Müller’s muscle), both of which are responsible for lifting the eyelid. The connective tissue between the levator muscle and the superior rectus muscle (the common sheath) extends forward to support the upper conjunctival fornix (superior suspensory ligament of the fornix).

Fig. 2.4 Histological section of the upper lid corresponding to the cross-sectional diagram of Fig. 2.3.

Fig. 2.5 Sections of the lower lid show the arrangement of the lower lid retractors. A condensation of fascia around the inferior oblique muscle forms the inferior suspensory ligament of the globe (Lockwood’s ligament). This is analogous to Whitnall’s ligament in the upper eyelid. It is attached medially and laterally in the region of the canthal tendons and can support the globe if the orbital floor is removed. The inferior aponeurosis extends forwards from Lockwood’s ligament with the inferior tarsal muscle (analogous to Müller’s muscle in the upper lid). These are the lower lid retractors which are responsible for depressing the lower eyelid on downgaze due to their connection with the inferior rectus muscle. A forward extension of the connective tissue associated with the lower lid retractors forms the inferior suspensory ligament of the fornix and anterior part of Tenon’s capsule.

Fig. 2.6 Histological section of the lower lid corresponding to the cross-sectional diagram of Fig. 2.5.

Fig. 2.7 Congenital lid colobomas are the result of a failure of normal development of the eyelid and closure of the facial clefts. Urgent repair is required only if the defect is so severe that the cornea is likely to suffer permanent damage from exposure.

Fig. 2.8 Epicanthic folds are abnormal folds of skin at the medial canthus. They are common in childhood, especially in children of oriental origin, but they may also be acquired as a result of tissue loss from trauma. Congenital epicanthic folds frequently give an appearance of pseudostrabismus (see Ch. 18). They usually become less obvious with age but, if they persist, both congenital and acquired folds can be treated by a variety of plastic surgery procedures.

Fig. 2.9 Blepharophimosis. These patients have epicanthus inversus, telecanthus and ptosis as well as blepharophimosis. Lower lid ectropion may also be present. Levator function may be poor; some patients have a dominant family history.