29 Surgical Management of Levator Function Less Than 4 mm
Abstract
Frontalis slings are used to treat congenital or acquired ptosis with a levator palpebrae superioris excursion of less than 4 mm. Many patterns for sling placement and different materials have been reported over the past few decades. This chapter describes a simplified triangular pattern using silicone rods. The procedure is simple to perform with fewer incisions than other methods. The most common complications are undercorrection and late slippage. Fixation of the sling material to the tarsal plate using a nonabsorbable suture through an upper lid crease is preferable to stab incisions and no fixation, as the former has a better chance of creating a symmetric skin crease and avoiding upper lid lash ptosis, and it reduces the risk of recurrent ptosis from late sling slippage.
29.1 Introduction
The surgical procedure commonly performed for congenital or acquired ptosis with a levator excursion of less than 4 mm is the frontalis sling, also termed “brow suspension,” in which the upper eyelid is elevated by linking the tarsal plate to the frontalis muscle using a sling or an advancement flap from the frontalis muscle. 1 , 2 Levator resection in these cases typically is inadequate to correct the ptosis.
29.2 History of Frontalis Sling
Many variations of frontalis sling patterns, sling materials, and fixation methods have been performed through the years. A brief discussion of each follows.
29.2.1 Patterns of Sling
One of the first patterns for sling placement was the triple triangle, popularized by Jack Crawford (Fig. 29.1). 3 Over the years, less elaborate patterns have been described eliminating the need for an incision in the mid-forehead region, including the double triangle, the rhomboid, and the square (Fig. 29.2). 4 , 5 This chapter describes a simplified technique using a single triangle pattern (Fig. 29.2).
29.2.2 Sling Materials
Autogenous, homologous, and alloplastic materials have been used as sling materials. 4 , 6 , 7
Autogenous tissues can be harvested from the leg (tensor fascia lata), arm (palmaris longus), and temple (temporalis fascia). 2 , 8 , 9 These are well tolerated, integrate well, and have low ptosis recurrence rates but require additional operative sites, special surgical equipment and time, and occasionally can have donor site morbidity. 7 , 10
Homologous banked fascia lata avoids the need to harvest tissue but requires a tissue bank and may be less durable than autogenous choices. In addition, the risk of transmissible infections such as prion disease must be considered.
Popular alloplastic materials for frontalis slings include Mersilene polyester mesh, 11 expanded polytetrafluoroethylene (ePTFE) 12 or Gore-Tex, polypropylene (Prolene suture), supramid (polyfilament), and silicone rods. 13 These all have the benefit of avoiding extra surgical time and donor site morbidity from harvesting autogenous tissue. They are more likely to slip over time, and all of them may become exposed or cause foreign body granulomas. 11 ID#b2a289a144_12 – 13 Silicone rods have the benefit of inherent elasticity, which may allow better eyelid closure. A Cochrane systematic review is currently being conducted to compare different materials for frontalis slings. 14
29.2.3 Fixation of Sling to Eyelid Tarsus
There are two common methods to fixate the distal loops of the sling material close to the eyelid margin. The first choice places small stab incisions through skin down to the tarsal surface, and the suspensory material is then drawn through the subcutaneous space using a Wright fascia needle that is threaded from one stab incision to the other (Fig. 29.3 a). This approach limits surgical dissection but does not allow creation of a defined lid crease. While fascia may be well integrated through this approach and limit slippage, several studies have shown a higher incidence of late slippage and recurrent ptosis in alloplastic sling cases. 1 , 15 In addition, upper lid lash ptosis (epiblepharon) is a common complication resulting from disruption by the sling. 16
In the second approach, an upper lid crease incision symmetric with the opposite side is created through skin and orbicularis muscle, and the pretarsal plateau is exposed centrally approximately halfway down its width. The loops of the sling material are attached to the tarsus using nonabsorbable suture placed partial thickness (Fig. 29.3 b). Late slippage and secondary eyelash ptosis are less frequent with this approach. The skin is closed with two to three deep bites to the leading edge of the levator muscle without nicking the sling material, thus avoiding eyelash ptosis. 16
29.3 #Indications
Frontalis sling is used in any form of congenital or acquired ptosis with poor levator excursion (less than or equal to 4 mm).
Elevate the eyelid to prevent childhood amblyopia.
Improve stereopsis in children and adults.
Improve superior field of vision.
Create aesthetic symmetry and so improve self-esteem.
29.4 Consequences
Lagophthalmos at night on gentle eyelid closure.
Reduced closure with blinking.
Increased palpebral fissure (eyelid retraction) on downgaze, particularly noticeable in unilateral cases.
Exacerbation of dry eye with associated discomfort or visual blurring.
29.5 Unique Considerations in Frontalis Suspension
29.5.1 Congenital Cases
A special consideration for children aged less than 8 years is the risk of deprivation amblyopia from the lid obscuring the visual axis. Young infants may require urgent surgery within a week to reduce the risk of amblyopia (Fig. 29.4). The presentation of congenital ptosis with poor levator excursion may be unilateral or bilateral, and isolated or associated with a syndrome such as Marcus Gunn jaw-wink, monocular elevation palsy, or blepharophimosis ptosis epicanthus inversus syndrome.
Marcus Gunn Jaw-Winking Ptosis
A pronounced jaw-wink may be treated by transecting the levator muscle close to Whitnall’s suspensory ligament. In milder cases, the levator may be left alone as the patient often learns through practice how to avoid jaw muscle movements that precipitate the levator stimulation. Some surgeons advocate severing the opposite normal levator muscle and then placing slings in both lids, while others recommend bilateral slings without dividing the contralateral levator. 17 I leave the normal eyelid untouched but warn the patient that some asymmetry will be present, particularly with fatigue of the frontalis muscle.
Blepharophimosis Ptosis Epicanthus Inversus Syndrome
The levator slings are usually performed after the telecanthus and epicanthal folds are repaired, although recent literature has focused on one-stage surgery (Fig. 29.5). 18
29.5.2 Acquired Cases
Acquired myopathic ptoses with poor levator excursion may be a result of trauma, of a third nerve palsy, or of a heritable genetic disorder.
Genetically Inherited Myopathic Ptoses
Causes of acquired ptosis with poor levator excursion include myogenic ptosis in which the levator muscle is severely impaired from mitochondrial myopathies, oculopharyngeal dystrophy, myotonic dystrophy, or other progressive myopathies described in Chapter 31 (Fig. 29.6). 19 In early mitochondrial myopathy, the levator function may be sufficiently strong (between 5 and 10 mm) to allow levator resection as repair. However, the natural history is for the disease to progress and recurrent ptosis is inevitable. Rather than subjecting the patients to repeat levator resections, many surgeons would recommend frontalis sling after the first recurrence.
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