Tarsal strip canthoplasty

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CHAPTER 32 Tarsal strip canthoplasty

Richard D. Lisman, Gary J. Lelli, Jr.

History

Suspension of the tarsus of the lower eyelid was originally described by Lexer and Eden in 1911.1 Since that time, multiple modifications have been made, most notably by Tenzel,2 Anderson and Gordy,3 Whitaker4 and Ortiz-Monasterio and Rodriguez.5 Alteration in the contour and position of the lower eyelid carries many names. It has been described as the tarsal strip procedure, the lateral canthal sling, lateral canthopexy, lateral canthoplasty, the tarsal tongue, the periosteal strip, horizontal shortening and tarsal suspension.6 While initially described for treatment of functional malposition of the eyelid, current use of the tarsal strip procedure includes many aesthetic adaptations.

Physical evaluation

• Attain a thorough history of ocular and eyelid symptoms, past medical and ocular history (with particular attention to the presence of rosacea, blepharitis, or other cicatricial diseases and thyroid associated orbitopathy) and past surgical history (with attention to any history of prior eyelid or facial cosmetic surgery and trauma).

• Check visual acuity in each eye.

• Examine the contour and position of the lower eyelid – evaluating the distance of the center of the mid-pupillary light reflex to the lower eyelid margin (MRD2) and the presence of inferior scleral show from lower eyelid retraction, ectropion or lower eyelid laxity.

• Determine the cause of lower eyelid malposition by examining for cicatricial changes (cicatricial etiology), facial asymmetry from seventh nerve palsy (paralytic etiology) or, most commonly, excessive laxity (involutional etiology).

• Evaluate lower eyelid laxity with the eyelid snapback test and the eyelid distraction test. The eyelid snapback test is performed by distracting the lower eyelid inferiorly toward the inferior orbital rim. Normal snapback occurs spontaneously. Quantification of abnormal lower lid laxity can be ascertained by counting the number of blinks required for the lid to return to its normal position against the globe. The eyelid distraction test is an estimation of the distance the lower eyelid can be pulled directly off of the globe.

• Ascertain the risk of developing or presence of keratopathy by assessing lagophthalmos during gentle closure and the presence of punctate corneal fluorescein staining (superficial punctate keratopathy).

• Manually elevate and retroplace the lower eyelid at the lateral canthus with a single digit to determine if tarsal shortening and suspension alone will result in adequate lower eyelid shape, contour and position against the globe.

Technical steps

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.

image

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:

1. Local anesthesia.

2. Lateral canthotomy.

3. Inferior cantholysis.

4. Release the orbital septum.

5. Development of the strip.

6. Opening of a periosteal slot.

7. Reattachment of the strip.

8. Resupporting the strip.

9. Lateral canthal angle reformation.

10. Closure of the lateral skin incision.

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

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