The frontalis sling is a specialized surgical procedure designed to correct severe eyelid drooping, known as ptosis. This technique bypasses the weakened natural eyelid lifting mechanism by connecting the eyelid directly to the forehead muscle, the frontalis muscle. The operation transfers the function of eyelid elevation from the compromised internal muscle, the levator palpebrae superioris, to the much stronger frontalis muscle. By raising the eyebrows, the patient can actively lift the eyelid through the implanted sling material. This mechanical solution is reserved for cases where simpler eyelid repair methods are ineffective due to severe muscle dysfunction.
The Condition Requiring the Sling
The frontalis sling procedure is indicated for patients suffering from severe ptosis who exhibit minimal or no function in the levator palpebrae superioris muscle. This primary eyelid elevator muscle is responsible for the majority of the eyelid’s movement; poor action is defined as less than 4 to 5 millimeters of lift. When the levator muscle is significantly compromised, procedures that tighten or advance it, such as levator resection, are unlikely to provide sufficient correction.
Severe ptosis can be congenital (present from birth) or acquired later in life. Congenital ptosis often results from levator muscle dysgenesis, where the muscle tissue develops abnormally. Acquired severe ptosis can stem from conditions like myasthenia gravis, chronic progressive external ophthalmoplegia, or significant third nerve palsies, which severely impair levator function. The inability of the eyelid to lift adequately can obstruct the visual axis, especially in children, potentially leading to developmental vision problems like amblyopia.
Surgical Mechanics and Materials
The mechanical principle involves creating a direct connection between the tarsal plate, a dense connective tissue layer within the eyelid, and the frontalis muscle in the forehead. The surgeon makes small incisions in the eyelid and above the eyebrow to create a subcutaneous tunnel for the sling material. The material is threaded in a specific configuration, often forming a pentagonal or triangular loop, secured to the tarsus at the eyelid margin, and anchored to the frontalis muscle or the periosteum of the brow. This arrangement ensures that the conscious effort to raise the eyebrows is transmitted directly to the eyelid, achieving elevation.
The choice of sling material is a significant consideration, broadly categorized as autogenous or alloplastic.
Autogenous Materials
Autogenous materials, such as fascia lata, are harvested from the patient’s own body, typically a strip of fibrous tissue taken from the thigh. Autogenous fascia lata is favored for its biological compatibility, leading to a lower risk of infection and a durable result. However, harvesting the fascia lata requires a second surgical site, which prolongs the procedure and introduces the potential for donor-site complications and pain.
Alloplastic Materials
Alloplastic, or synthetic, materials offer an alternative that avoids the need for a second incision. Commonly used synthetic options include silicone rods, expanded polytetrafluoroethylene (Gore-Tex), and various non-absorbable sutures. Silicone rods are popular due to their elasticity, which allows for dynamic movement and easier post-operative adjustment. However, alloplastic materials carry a higher risk of complications such as foreign body reaction, granuloma formation, or infection, which may necessitate removal of the sling material.
Candidate Criteria and Post-Operative Care
Patient selection is based on the severity of the condition and the patient’s underlying muscle function. The most ideal candidates are children with severe congenital ptosis and poor levator function, as early intervention can prevent vision loss. Adults with acquired conditions like chronic progressive external ophthalmoplegia or myasthenia gravis that have not responded to medical treatment are also candidates. A prerequisite for success is that the patient must have adequate function of the frontalis muscle, as this muscle serves as the new power source for eyelid movement.
The immediate post-operative period is characterized by swelling and bruising around the eye and forehead, which typically subsides within a few weeks. A common side effect is lagophthalmos, the inability to fully close the eye, particularly during sleep, because the sling lacks the fine control of the natural muscle. Patients must meticulously follow a regimen of eye lubrication, using artificial tears during the day and ointment at night, to prevent corneal exposure and dryness. The sling mechanism also often results in a “tethering” effect on downward gaze, meaning the eyelid does not lower as easily as a normal eyelid. Follow-up care is important, as risks like recurrence of the ptosis, infection of the sling material, or the need for minor adjustments to the sling tension can occur over time.