Anatomy

Thorough understanding of eyelid and periocular anatomy is paramount in order to successfully perform lateral canthal surgery. The lateral canthal tendon inserts inside the lateral orbital rim just superior to the horizontal midline at Whitnall’s tubercle. Palpation of a skull is helpful to grasp the depth of Whitnall’s tubercle, which allows the surgeon to understand the necessity of reattachment of the tarsal strip posterior to the orbital rim to assure appropriate lower eyelid apposition to the globe laterally. The lateral canthal tendon is an extension of the orbicularis oculi muscle of the upper and lower eyelid that attaches to the periorbita overlying the bone. The orbicularis muscle is separated into pretarsal, preseptal and orbital components. The continuation of the pretarsal and preseptal orbicularis muscle of the upper and lower eyelid taper to form the superior and inferior crus of the lateral canthal tendon. When surgically correcting lower eyelid malposition with a tarsal strip procedure, only the inferior limb is released, thereby not affecting the upper eyelid position.

Structurally, the eyelid is divided into anterior, middle and posterior lamellae. The anterior lamella is comprised of skin and orbicularis oculi muscle. The middle lamella contains orbital septum and orbital fat. The posterior lamella of the lower eyelid is made up of tarsus, lower eyelid retractors (capsulopalpebral fascia and inferior tarsal muscle) and conjunctiva. In fashioning a tarsal strip, the anterior and posterior lamellas are split. See Fig. 32.1 for a summary of relevant eyelid and periocular anatomy.

Fig. 32.1 Parasagittal section of eyelid and orbital anatomy. 1. Superior rectus muscle. 2. Levator muscle. 3. Conjoining of SRM with levator muscle sheath. 4. Tenon’s capsule. 5. Suspensory ligament of superior fornix. 6. Whitnall’s ligament. 7. Frontalis muscle. 8. Brow fat pad. 9. Orbital orbicularis. 10. Arcus marginalis. 11. Orbital septum. 12. Preaponeurotic fat pad. 13. Preseptal orbicularis. 14. Postorbicularis fascia. 15. Levator aponeurosis. 16. Superior conjunctival fornix. 17. Müller’s muscle. 18. Conjunctiva. 19. Superior tarsus. 20. Pretarsal orbicularis. 21. Inferior tarsus. 22. Musculocutaneous retractor insertion. 23. Conjunctiva. 24. Inferior conjunctival fornix. 25. Tenon’s capsule. 26. Inferior orbital septum. 27. Lockwood’s ligament. 28. Inferior tarsal muscle. 29. Suspensory ligament of inferior fornix. 30. Inferior oblique. 31. Capsulopalpebral fascia. 32. Inferior rectus muscle.

The normal slope of the lower eyelid is slightly upward from medial to lateral, placing the lateral canthus approximately 1–2 mm above the medial canthus. When the lateral canthal angle is lower than the medial canthal angle, this is termed an anti-mongoloid slant. An excessive upward slant of the lateral canthal angle is known as a mongoloid slant. While traumatic lateral canthal dystopia and syndromes can account for these alterations, normal variants are more common. Examination of a patient from the side allows comparison of the anterior aspect of the globe to the lower eyelid and malar eminence. If a negative vector exists, canthal surgery can result in tethering of the eyelid beneath a prominent globe.⁷ Since both symmetry and stability of facial appearance are important components of any lower lid repositioning procedure, photographs of the patient at a younger age often aid in determining what is “normal” for that individual.

Lateral tarsal strip technical steps

The lateral tarsal strip operation can be broken down into the following steps, which are reviewed in detail below:

The majority of isolated lateral tarsal strip procedures can be performed under local anesthesia with monitored anesthesia care. After sedation, protective corneal shields are inserted into each eye for safety. Approximately 2.5 mL of 1% lidocaine with 1 : 100,000 epinephrine are injected subcutaneously in the lateral half of the lower eyelid. With the non-dominant finger placed inside the lateral orbital rim, the needle is directed perpendicular to the skin at the lateral orbital rim and advanced to bone for anesthesia and hemostasis.

A number 15 blade is used to create a lateral canthal incision in an aesthetically pleasing skin fold of approximately one centimeter (Fig. 32.2A,B). With upward traction on the lateral aspect of the lower eyelid, the inferior crus of the canthal tendon is severed with Stevens scissors (Fig. 32.3A,B). The scissors are directed posteromedially and the orbital septum is released with sharp dissection (Fig. 32.4). If adhesions are present along the septum and/or retractors from prior surgery, these can be bluntly lysed by placing the scissors through the canthal opening and spreading across the middle lamella.

Fig. 32.2 Lateral canthal incision.

Fig. 32.3 Inferior cantholysis.

Fig. 32.4 Orbital septal release.

At this point, the lower lid is fully mobile and determination of the appropriate length of strip is ascertained by pulling the lower lid laterally and slightly superiorly towards Whitnall’s tubercle until appropriate height, tension and contour are achieved. Development of the tarsal strip is begun by splitting the anterior and posterior lamella of the lateral lower lid at the grey line with a supersharp blade (Katena instruments #K20-1058, 30°, 3.5 mm) or a number 15 blade (Fig. 32.5A,B). The split is carried for the pre-determined length necessary to give normal lower eyelid tension and contour. Blepharoplasty scissors are used to remove the anterior lamella and cilia from the proposed length of the tarsal strip (Fig. 32.6A,B). Similarly, the mucocutaneous junction is excised. It is not necessary to remove conjunctiva from the strip since it is a non-keratinizing surface. A back-cut through the conjunctiva and lower eyelid retractors is made at the inferior tarsal border for the length of the strip, thus completing formation of the strip (Fig. 32.7).

Fig. 32.5 Splitting of the anterior and posterior lamella. Note the ability to fully distract the lower lid from the globe secondary to complete release of the inferior crus of the canthal tendon and orbital septum.

Fig. 32.6 Excision of anterior lamella and cilia.

Fig. 32.7 Completion of the lateral tarsal strip.

A periosteal slot is indirectly opened at the inner aspect of the lateral orbital rim with a number 15 blade (Fig. 32.8). The soft tissues are pushed with a swab to indirectly feel the lateral orbital rim. If direct exposure is created by incising down to the rim, significant postoperative edema is produced since two-thirds of the lymphatic for the upper and lower eyelid drain at the lateral orbital tubercle. Any bleeding is controlled with unipolar cautery prior to suturing of the strip to the orbital periosteum.

Fig. 32.8 Opening the periosteal slot.

The strip is led beneath the periosteum at the inner aspect of the superolateral orbital periosteum with a double-armed 4-0 Polydek suture on a P-2 needle passed in a mattress fashion (Fig. 32.9). The two arms of the suture are passed in the opening created in periosteum. This opening can be widened with a sharp cautery tip to help obtain both hemostasis and ease of entry. The superior suture is grasped first and using retraction to expose the lateral rim, the suture placed within the two leaves of periosteum within the rim. Lid height and contour is assessed by pulling the upper suture. If necessary, the suture can be backed out and repassed to improve contour or height. Once the upper suture is satisfactory, the lower tarsal suture is passed in a similar fashion through the inner orbital periosteum approximately 2–3 mm inferior to the other suture arm. Adjustments in the vector, height and location within the lateral orbital periosteum of this suture pass give the surgeon options for postoperative contour, lid level, tension and apposition to the globe (Fig. 32.10). The lower limb of the suture can be inferiorly placed to lower the eyelid placement, if needed. This suture must be cut close to the knot. Any exposed Polydek is prone to deeper epithelial inclusion cysts from this braided, non-absorbable suture.

Fig. 32.9 Attachment of the strip to the periosteum.

Fig. 32.10 Flexibility in periosteal suture placement.

The strip is resupported and the permanent suture is covered with a 4-0 PDS suture passed in an interrupted fashion through the strip and secured to the periosteum (Fig. 32.11). Fine adjustments can be made in lid height and contour with this suture pass. The rim can be “walked” superiorly or inferiorly to gain a second attempt at a good position or symmetry with the contralateral eyelid.

Fig. 32.11 Resupporting the strip. Note that the Polydek suture is not visible after placement of the PDS suture.

Closure begins by reforming the lateral canthal angle. This is achieved with two interrupted 6-0 chromic sutures. The sutures are passed percutaneously through the upper eyelid, entering just superior to the eyelashes and exiting just posterior to the eyelashes. A mirror image of this pass is performed in the lower eyelid and the sutures secured, concentrating on achieving a symmetric and acute shape to the canthal angle (Fig. 32.12). A single interrupted 6-0 silk suture is passed over the chromic sutures for additional support (Fig. 32.13). The lateral canthal skin incision is closed with interrupted 6-0 silk sutures. The corneal shields are removed. Ophthalmic ointment is applied to the wound and the eye. Patching is not required. Ice compresses are started in the recovery room.

Fig. 32.12 Reformation of the lateral canthal angle.

Fig. 32.13 Support of the canthal angle reformation.

Pre- and postoperative photographs of a typical patient are shown in Fig. 32.14A–C. The tarsal strip procedure can be used for aesthetic enhancement of the lateral canthal angle and palpebral aperture (Fig. 32.15A,B). Additionally, one can cosmetically improve upsweep of the lower eyelid contour without influencing the height of the lower eyelid (Fig. 32.16A,B). Functional improvement of lower eyelid ectropion is shown in Fig. 32.17A,B.

Fig. 32.14 Photos of preoperative (A); 3 days (B); and 3 months postoperative appearance (C).

Fig. 32.15 Pre- (A) and postoperative (B) photographs of tarsal suspension surgery for aesthetic improvement of lateral canthal angle and aperture size.

Fig. 32.16 Pre- (A) and postoperative (B) example of improved upsweep of the lower eyelid without change in eyelid height.

Fig. 32.17 Pre- (A) and postoperative (B) demonstration of functional repair for lower eyelid ectropion and conjunctival keratinization.