13 Internal Ptosis Repair
Conjunctival Müller muscle resection (CMMR) is a reliable and technically facile approach to ptosis repair. Based on results of the phenylephrine test during a preoperative evaluation, surgical outcome can be highly predictable. For patients who require eyelid elevation of up to 3 mm, CMMR (internal ptosis repair) is an excellent surgical option. The success of the CMMR is manifest in its wide adoption by oculoplastic surgeons who had previously favored an external approach to ptosis repair.
To provide a step-by-step approach to preoperative evaluation of ptosis.
To provide the surgical steps necessary to complete internal ptosis repair.
To provide tips and pearls regarding surgical technique and postoperative management.
Patients with small amounts (<3 mm) of involutional ptosis and good levator function (LF) who have a good response to phenylephrine may benefit from internal ptosis repair. The advantages of the conjunctival Müller muscle resection (CMMR) involve its predictability, ease of operation, and lack of an external incision. Results of external levator advancement vary considerably, and the need for reoperation may be as high as 8.7%. 1 Tarsal removal in the Fasanella–Servat procedure can lead to tenting, abnormal lid contour, and conceivably keratitis sicca via its removal of Meibomian glands. 2 The success of the CMMR is manifest in its wide adoption by oculoplastic surgeons who had previously favored an external approach to ptosis repair. 3
To elevate the upper eyelid so that it may clear the visual axis.
To determine the amount of ptosis, measured by the MRD1, in order to decide on an approach for treatment.
Internal ptosis repair is typically chosen for cases in which the eyelid requires up to 3 mm of elevation.
If the amount of required elevation significantly exceeds 3 mm, ptosis repair by external levator advancement is preferred.
13.4 Key Principles
The eyelids serve to protect and lubricate the globe. Normal positioning of the eyelids is important in maintaining these functions. The upper lid has a more arched contour than the lower lid, with the peak of the upper lid located just nasal to the pupil. 4 The palpebral fissure, the distance between the upper and lower eyelids, is approximately 9 to 10 mm. The position of the upper eyelid is measured using the MRD1 which represents the number of millimeters between the corneal light reflex and the upper lid margin, a measurement that is integral to the identification and management of ptosis. The average measurement is between 4 and 5 mm.
There are two muscles that elevate the upper eyelid: the levator muscle and the Müller muscle. The levator is a voluntary, skeletal muscle innervated by the oculomotor nerve and it is the main retractor of the upper eyelid. The levator courses anteriorly from the orbital apex to below the orbital roof where it subsequently becomes an aponeurosis that extends inferiorly into the eyelid, inserting onto the anterior aspect of the tarsus. Several extensions of the aponeurosis extend anteriorly through the orbicularis muscle to create the upper eyelid crease.
Müller muscle is a diaphanous structure that has an involuntary eyelid elevation function. The muscle is located under the levator aponeurosis and anterior to the conjunctiva, beginning at the superior border of the tarsal plate and extending to Whitnall ligament. The Müller muscle is not as powerful as the levator in terms of its elevating capacity; it is, however, innervated by sympathetics, and contributes to the eyelid changes associated with a ‘fight or flight’ response. 4 Loss of sympathetic tone, which is seen in Horner syndrome, results in a mild ptosis and would not cause a complete ptosis.
Ptosis refers to drooping of the upper eyelid. Although there are many different types of ptosis, most cases can be classified as congenital, involutional, or as a result of trauma/associated medical condition. The amount of ptosis, measured by the MRD1, helps to determine the approach for surgical treatment. The other important factor in determining the surgical plan is the amount of LF; this is defined as the amount of movement (measured in millimeters) of the eyelid from extreme downgaze to extreme upgaze and is normally 14 to 16 mm. 4 Congenital ptosis is associated with poor LF, and therefore usually requires treatment with a frontalis sling. Involutional ptosis, which is the cause of the majority of adult-onset ptosis, is typically associated with normal or near-normal LF. In the setting of good LF, surgical options include an external levator advancement (ELA) or internal ptosis repair known as a conjunctival Müller muscle resection (CMMR).
This chapter will help guide the identification of cases in which internal ptosis repair is appropriate and provide surgical pearls for excellent function and cosmesis.
Internal ptosis repair is indicated for mild ptosis (<3 mm) in patients who show a positive response to the phenylephrine test which is discussed below.
Internal ptosis repair does not require suturing of the skin, so for patients concerned about postoperative scarring and recovery, this may also be indicated.