Ординатура / Офтальмология / Английские материалы / Oculoplasty and Reconstructive Surgery Made Easy_Garg,Touky, Nasralla_2009

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contraction. The transmission of frontalis muscle activity to upper lid is achieved by the insertion of a biologically acceptable non-stretchable rodshaped connection between the two. The mechanism of lid elevation after brow suspension is totally different from the mechanism when the levator muscle is lifting the lid. Normally, the elevating force vector of the levator muscle on the upper lid is superio -posterior. This is due to the pulley effect of Whitnall’s ligament, which diverts the anteroposterior contractile fore of the levator muscle to a more superio-posterior direction.

In frontalis muscle suspension where the sling material is passed at a more superficial level from he brow to the anterior eyelid layers, the brow transmits a superior, and frequently, an anterosuperior elevating force to the upper eyelid. This superior vector tends to pull the upper lid away from the globe and presents an even greater problem in patients with prominent brows or deep set eyes. The line of pull also tends to obliterate, rather than form, a lid crease.

This antro-superior elevating force could be directed posteriorly by placing the suspensory material behind the septum. Several problems arise from posterior placing of the sling. Depending on its nature, it might adhere to the septum and leave the upper lid at a frozen level. There is increase in the incidence of lagophthalmos and exposure keratopathy. If infection occurs it may result in an orbital space infection.

The ideal material used in frontalis sling should be chemically inert, noncarcinogenic capable of resisting mechanical stress, sterilizable, yet not physically modified by tissue fluids, dose not excite an inflammatory of foreign body reaction, not induces a state of allergy or hypersensitivity.

Several sling materials have been used; as fascia lata (autogenous or preserved); synthetic materials as silicone rods, sutures and meshes.

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The frontalis muscle flap advancement is a technique of direct transfer of the force of the frontalis muscle to the eyelid without the insertion of fascia, suture or a graft between the muscle and the tarsus. Frontalis suspension by frontalis muscle flap is a well-accepted method of treating severe bleharoptosis. Being from the same patient, there is no risk of rejection or severe body reaction as may occur with homogenous or alloplastic materials. There is no risk disease transmission. A Frontalis flap grows with the child’s growth and does not lead to cheese-wiring as synthetic materials. The frontalis muscle is well-developed before fascia lata maturation. Therefore, this procedure can be performed earlier, if indicated, in cases of infantile ptosis. Additional advantages of this technique include its technical simplicity, lack of remote scar as the donor site is in the primary surgical field, minimal ptosis on upgaze, less lid lag on downgaze, preservation of eyelid contour and less tendency for the lid to pull away from the eye. In contrast to traditional frontalis slings, only one 2 cm brow incision is required.

The mechanism of frontalis suspension surgery is to transfer the upward traction produced by the frontalis muscle to the eyelid. Most techniques described the transfer of this traction by the way of the insertion of a suture material or graft between the frontalis muscle and the tarsus. It seems that the relocation of the frontalis muscle insertion to the eyelid would be the ideal way to elevate the eyelid by direct frontalis muscle action. This direct linkage of the frontalis muscle to the eyelid has been documented by postoperative magnetic resonance imaging scan.

The frontalis muscle flap lifts the eyelid thorough natural contraction of the muscle, directly transferring the upward traction of the frontalis to the eyelid. The frontalis muscle itself is the ideal suspensory material for ptosis repair, especially

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in patient with poor levator function or previously failed levator resection surgery, yet its use largely has been overlooked.

ANATOMY OF THE OCCIPITOFRONTALIS

Occipitofrontalis covers the dome of the skull from the highest nuchal lines to the eyebrows. It is a broad musculofibrous layer consisting of four thin, quadrilateral parts—two occipital and two frontal connected by the epicranial aponeurosis. Each occipital part (occiptalis) arises by tendinous fibers from the lateral two-third of the highest nuchal line of the occipital bone and the mastoid part of the temporal bone, and ends in the aponeurosis. Each frontal part (frontalis) is adherent to the superficial fascia, particularly of the eyebrows.It is broader than the occipital part and has fibers that are longer and paler.

Although frontalis has no bony attachments of its own, the medial fibers are continuos with those of procerus muscle, the intermediate fibers blend with corrugator supercilii and orbicularis oculi muscles. And the lateral fibers also blend with orbicularis over the zygomatic process of the frontal bone. The frontalis muscle is closely adherent to the skin and subcutaneous tissues at the eyebrow region but is mobile on the underlying periosteum due to loose areolar connections between the frontalis and the periosteum of the supraorbital rim. From theses attachment the fibers ascend to join aponeurosis in front of the coronal suture. The medial margins of the frontal bellies are joined together for some distance above the root of the nose, but between the occipital bellies there is a considerable, though variable, gap occupied by an extension of the epicranial aponeurosis. Contraction of the frontalis muscle elevates the eyebrows strongly and the eyelids weakly.

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The blood supply of the frontalis muscle is via the supraorbital, the supratrochlear and the superficial temporal arteries. Sensory branches of the supraorbital nerve course upwards over the frontalis muscle. The frontal or temporal branch of the facial nerve passes approximately 1.5 cm at the lateral brow to enter the undersurface of the frontalis muscle no higher than 2 cm above the eyebrow.

EVALUATION OF THE PATIENT

This procedure can be conducted on patients with ptosis and eyelid excursion measured as poor or less than 4 mm. The etiology of ptosis can be congenital or acquired.

Patients should subjected to full ophthalmological examination.

Slit lamp examination, fundus examination and refraction must be done. Best corrected visual acuity and presence or absence of amblyopia must be noted. Extraocular muscle functions must be evaluated for any associated abnormalities. Patients should be tested for jaw winking, Bell’s phenomenon and abnormal head posture. Orbicularis muscle function must be assessed by noting eyelid closure. Measurement of the eyelid crease to determine the site of lid incision must be done.

The forehead must be examined to detect any abnormality as well. This surgery has an effect similar to a brow lift in that it affects forehead wrinkles and therefore is best indicated for patients with bilateral ptosis or unilateral ptosis with a smooth forehead preoperatively.

The amount of ptosis is measured using the margin reflex distance 1 (MRD 1), which is the distance from the light reflex to the center of the upper lid margin in primary position. Measurement of the vertical interpalpebral fissure height is also recorded. Measurement of levator muscle function by measuring the excursion of the upper eyelid from down gaze

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to upgaze with the frontalis muscle fixed is done. Cases with 5 mm or more of function should undergo levator muscle surgery. The procedure can be done on primary cases as well as cases with recurrent ptosis following previous levator muscle surgery or frontalis sling procedures.

SURGICAL TECHNIQUE

The frontalis muscle is exposed through a horizontal brow incision that begins 5 mm lateral to the supraorbital notch and extends laterally 2 cm on the upper border of the eyebrow parallel to the hair line. It is necessary to limit the lateral extent of the incision so the frontal branch of the facial nerve is not injured. A subcutaneous plane is then dissected downwards bluntly to free the frontalis from the brow till the orbicularis is seen, providing adequate length to be used in the flap formation. The anterior surface of the frontalis muscle is exposed by blunt dissection superiorly so that a superiorly based frontalis muscle flap can be designed. The frontalis muscle is incised along its attachment to the brow. Care is take to avoid injury to supra orbital nerve and vessels as they emerge from the notch.

Blunt dissection releases the under surface of the frontalis from the periosteum of the frontal bone, creating a flap 1 to 2 cm in length. Two vertical incision are made through the frontalis muscle parallel to the muscle fibers at the extremes of the eye brow incision to form a tongue of the frontalis muscle 7 to 12 mm in width to be advanced onto the tarsus. The dissection is performed so that the vertical height of the frontalis flap is 1 to 2 cm depending of the degree of ptosis and the power of the frontalis muscle.

An eyelid crease incision is made deep to the plane beneath the orbicularis oculi muscle to expose the tarsus

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downward. The dissection is continued superiorly to form a tunnel underneath the orbicularis muscle and then turns superficially to the subcutaneous plane by cutting the muscle layer transversely at the level of the inferior eyebrow margin. The inferior portion of the frontalis flap is then brought down through the tunnel above the septum and below the orbicularis and advanced onto the anterior surface of the tarsus.

The isolated flap is then fixated to the upper third of the tarsus with two – interrupted mattress sutures of 6-0 polypropylene.

In cases of bilateral ptosis the eyelid margin position is set at or 1 mm above the limbus on both sides, because the lid will lower approximately 2 to 3 mm when orbicularis function returns and gravity forces the eyebrow down in the upright position.

In unilateral cases, the lid should be set 2 to 3 mm above the level of the non-ptotic lid. Because of a tendency to undercorrection, we recommend suturing the side of the flap to the original frontalis muscle helping to maintain the level of the lid higher as needed. This modification reduces the incidence of late undercorrection that is reported with this technique, suspected to be due to gradual stretching of the flap.

The lid crease incision and eyebrow incision are sutured by 6-0 polypropylene in older children and adults, or 6-0 chromic cat gut in younger children. Polypropylene skin sutures are removed after 5 days, and ophthalmic antibiotic ointment is applied at bedtime for 2 weeks or until lagophthalmos resolve.

Our technique for frontalis muscle advancement differs from previously described technique, which likely explains our successful use of this procedure. Part of the frontalis muscle insertion is transferred directly to the eyelid in our

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surgical technique. We make the frontalis flap rectangular and base it superiorly, in contrast to the earlier reports of a superolaterally placed L – shaped flap. This distributes the pull of the frontalis muscle on the tarsal plate.

Our results suggest that a flap width of 7 mm in younger children and 12 mm in older ones provides adequate elevation if properly centered over the tarsus. Also, the tenting deformity described earlier, was not seen, likely because we make the flap in a rectangular fashion and undermine the flap as high as necessary to prevent overcorrection by a tight flap.

It should be emphasized that the length of the flap is adjusted according to the degree of ptosis and the power of the muscle. The more pronounced the ptosis, the shorter the flap must be to elevate the lid adequately. In this aspect the flap acts like a harness, the shorter it is, the closer the insertion (tarsus) is to the origin (brow), i.e. the higher and taughter is the lid. Accordingly, based on this experience, we believe that adjustment of the lid height can be done using recession or resection of the flap in cases of under or over correction postoperatively. The advanced flap can be shortened directly in cases of residual ptosis. Also, it is not necessary to advance a thick, bulky flap, a thin flap will cause less eyelid fullness and still elevates the lid well.

Lastly, we now perform the entire procedure through a lid crease incision, there by minimizing brow scarring.

COMPLICATIONS

Residual ptosis of +2.00 mm or less occurs in about 10% of cases. These can be redone with our modified technique and corrected as explained earlier.

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Entropion can occur due to lower insertion of the flap in themiddlethirdofthetarsus.Itshouldbeimmediatelyrepaired by reinsertion of the flap in the upper part of the tarsus.

Late suture infection can be managed by removal of the suture, drainage of the pus and administration of systemic antibiotic. The flap is usually not affected nor its attachment to the tarsus. Suture infection and/or granuloma formation is a well-recognized complication of frontalis sling procedures. However, its treatment may necessitate removal of the sling and recurrence of ptosis.

Lagophthalmos is usually temporary in the first few weeks till edema resolves. It disappeares with the full recovery of orbicularis function and the patient can close his eyes by orbicularis contraction. Lubricants are prescribed until the lagophthalmos resolves.

Lid lag on down gaze and corneal exposure during sleep are potential complications of the procedure. In our cases, lid lag on down gaze occurred in almost all cases. It is an inherent side effect of all frontalis muscle surgery and should be wellexplained to the patients or their parents. However, it is usually accepted as the price for correction of the ptotic lid in primary position and in upgaze.

Asymmetry between the lids of more than 1 mm can occur in patients with unilateral surgery. For any technique of frontalis surgery to be successful, the patient should be stimulated to use the frontalis muscle to lift the ptotic lid.

Therefore, severe unilateral ptosis corrected only with a unilateral frontalis surgery causes “a functional undercorrection“ of the ptosis. The reason for this undercorrection is that the normal lid level on the contralateral side allows the patient to see well, and therefore, the patient is not stimulated to use the frontalis muscle. This is similar to the patient with jaw– winking phenomenon who learned to see well with either

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the contralateral eye in unilateral jaw–winking or with jaw movments in bilateral cases. This signifies the importance of documenting the trial to lift the lid preoperatively by the patient with frontalis contraction. The full correction of ptosis in the primary position can be noticed when the patient contractes the frontalis voluntarily especially in unilateral cases. A trial of occlusion of the sound eye can document the functional undercorrection and differentiate it from true anatomical undercorrection. Occlusion therapy (as in amblyopia cases) and excercises to develop and maintain binocular vision can help reducing this phenomenon.

Cases of over-correction rarely occurs. The postoperative lid height attained at 6 weeks visit is usually stable and maintained thereafter.

In conclusion, frontalis muscle flap advancement is a valuable technique in the management of severe ptosis with poor levator function in children and adults. Our modified technique helps to prevent postoperative under correction by preventing overstretch of the flap.