The Horizontal Dynamic of the Medial and Lateral Canthus

Abstract

The medial canthus and the lateral canthus are dynamic structures that move with horizontal eye movements in patients who have not undergone canthoplasty. The measured movement of the lateral canthus differed, based on the position from which the measurements were made, and was not always in the direction of the globe. The movement of the lateral canthus and the medial canthus differed on the right and left sides of the same subject.

Lateral Tarsal Fixation in Caucasians

“…3,6 Gioia et al 3 stated that although the lateral tarsal aspect was supported by the LCT, the lateral check ligament, including the lateral rectus muscle pulley, attached to the posterior aspect of the LCT. Jones 7 and Ruskel et al 8 stated that the distal extension of the lateral rectus muscle pulley (lateral check ligament) was inserted to the conjunctival fornix and not on lateral aspect of the tarsal plate.…”

Microscopic Findings of Lateral Tarsal Fixation in Asians

“…1 In this regard, the lateral tarsal strip procedure 22 is not appropriate, as it replaces the dynamic, flexible LCT with an inflexible fixation of the lateral tarsus to the orbital rim. 18 Also, it severs the connection of the lr-CPF to the tarsus. Thus, other techniques are needed that are less invasive to the lateral canthus and which can preserve the original lateral canthus anatomy.…”

“…18 The cause of this movement has been explained as intersubject variation in composition and configuration. 18 The lr-CPF changes its vertical position with aging, 19 which may be caused by laxity of the lr-CPF. Differences in lr-CPF laxity may contribute to any intersubject variation.…”

“…Thus, other techniques are needed that are less invasive to the lateral canthus and which can preserve the original lateral canthus anatomy. When there is horizontal laxity of the lower eyelid in the LCT, the lateral retinacular resuspension is an ideal procedure, 18,20,21 being one in which dynamic eyelid and canthal fixation are maintained with good aesthetics without canthotomy and cantholysis. On the other hand, when there is a horizontal laxity of the lower eyelid lying in the tarsus, e.g., seventh nerve palsy, 8 the horizontal shortening of Kuhnt-Szymanowsky with blepharoplasty is appropriate to treat the pathology.…”

“…In surgery, it is vital, as much as possible, not to injure the lateral canthal tissues 18,20,21 because the mobile lateral canthus is useful for increasing the temporal visual field during lateral gaze. 1 In this regard, the lateral tarsal strip procedure 22 is not appropriate, as it replaces the dynamic, flexible LCT with an inflexible fixation of the lateral tarsus to the orbital rim.…”