Lateral Canthus

    Despite varied anatomical descriptions and nomenclature, the lateral canthus should be considered in terms of a deep skeletal attachment via the lateral canthal tendon and a superficial fibrous attachment via the lateral canthal raphe and lateral orbital thickening. The deep attachment serves to stabilize the tarsal plates whereas the superficial attachment functions to stabilize the orbicularis over the orbital rim.

    The lateral canthal tendon is less well defined than the medial side and has less orbicularis muscle connecion. It takes the form of a Y-shaped fibrous condensation measuring 6 mm in transverse length and up to 10 mm in vertical height. It extends from the upper and lower tarsal plates and is reinforced by significant attachments from the lateral horn of the levator apo-neurosis and the check ligament of the lateral rectus muscle as well as from Lockwood's ligament. This confluence of structures (the lateral retinaculum) attaches to the lateral orbital wall at Whitnall's tubercle, which is located just inside the orbital rim and approximately 10 mm below the zygomaticofrontal suture. Whitnall's (superior transverse) ligament is part of the levator aponeurosis and is not part of the lateral canthus.


    Superficially, the preseptal orbicularis fibers of the upper and lower lid interdigitate to form the lateral canthal raphe. The raphe, although often referred to in eyelid texts, has not been clearly described and is difficult to identify as a discrete anatomical structure. It is connected on its deep surface to the underlying septum orbitale and merges laterally with a significant conflu-ence of fibrous tissue known as the lateral orbital thickening1. This thickening is a condensation of fascia passing over the orbital rim, lateral and superficial to the lateral canthal tendon. It has also been termed the 'superficial leaf of the lateral canthal tendon'10 and the 'precanthal web'." It is a triangular fibrous adhesion connecting the orbicularis fascia on the undcr-surface of the muscle to the underlying deep fascia, which in this region is made up of thickened lateral orbital rim peri-osteum and adjacent deep temporal fascia. The lateral orbital thickening is continuous with the orbicularis retaining ligament inferomedially and must be released surgically if a canthoplasty is to be effective.

    The lateral canthus is positioned approximately 2 mm higher than the medial canthus. Despite previous assumptions, this is the same for both sexes and does not change with increasing age.12 Inherent variations of the intercanthal angle do, however, have a significant impact on facial aesthetics in normal people and descent of the lateral commissure secondarily to lateral canthal tendon laxity produces an apparent change in the lateral canthus position, which predisposes to a premature aging appearance.