Recession or faden operation of the yoke muscle in the una ected eye is the preferred method to increase the

field of binocular diplopia-free field.

15

These are the general principles that the strabismus surgeon needs to consider in all types of paralytic strabismus cases. The cranial nerve palsies will be evaluated individually during the rest of the manuscript.

15.2 Third Nerve Palsy

Third nerve palsy may a ect the third nerve in total, or the superior or inferior branches of the nerve as well as the isolated EOM involvement. All these types of third nerve palsy may present with a total or partial involvement, and they represent a wide range of ocular motility problems. The involvement of the inferior branch of the third nerve a ects medial rectus, inferior rectus, and inferior oblique muscles, whereas the superior branch a ects the superior rectus and levator palpebrae superioris muscle.

15.2.1Complete Third Nerve Palsy

In complete third nerve palsy, the major problem is the unopposed contracture of the antagonist lateral rectus muscle. There is a small hypotropia with a large angle exodeviation and ptosis due to the involvement of levator palpebrae superioris muscle. If the pupillary fibers are a ected, a mydriatic pupilla will be observed. In congenital and long-standing cases, fibrosis of the intraorbital structures develops. The aims of treatment in complete third nerve palsy are to obtain an improvement of the appearance of the patient, orthophoria in primary position, and a field of binocular single vision in a very limited area. Prior to any surgical intervention, the patient must be informed about the goals of surgery and the possibility of a more bothersome diplopia with the decrease of the proximity of the two images in primary position.

The surgical treatment modalities in complete third nerve palsy may be summarized as follows:

■Weakening of the lateral rectus muscle.

■Resection of the medial rectus muscle.

■Superior oblique tendon transposition.

■The procedures that keep the eye in passive adduction.

eye, orbital wall periost fixation of the lateral rectus muscle, and BTXA injection in residual deviations [7–9]. Orbital wall periost fixation is a recently described method for the inactivation of lateral rectus muscle that we found useful in our clinical practice. Posterior Tenon fixation is proposed to be an alternative method to periost fixation [10]. The potential reversibility of the procedure is the advantage of both of these methods.

Medial rectus resection: Although the resection of a paralytic muscle is not so e ective, some authors prefer to perform a large resection to obtain a mechanical resistance against abduction. In our experience, this e ect does not last long and we do not prefer to resect medial rectus muscle.

Superior oblique tendon transposition: T he aims of superior oblique tendon transposition is to correct the hypotropia, making the superior oblique an adductor, creating a mechanical barrier against abduction, and thus preventing the recurrence of the exodeviation. Superior oblique tendon transposition may work if and only if the superior oblique muscle has some function. Especially, in long-standing ones, it may be di cult to assess the function of the superior oblique muscle while the eye is fixated in an abducted position. In such patients with no apparent hypotropia or intorsion in ocular motility examination, slit lamp observation may be very helpful. Any attempt of intorsion of the eye can easily be observed under slit lamp. Superior oblique tendon transposition may be performed by trochlear luxation and superior oblique tendon resection or with Scott’s method by cutting the superior oblique tendon via nasal approach and suturing the tendon 2 mm anterior and nasal to the superior rectus tendon without destroying the trochlea [7, 11]. The latter is our preferred method for superior oblique tendon transposition, which is a less invasive one.

The procedures to keep the eye in passive adduction: For a permanent e ect fascia lata, silicone band or superior oblique tendon may be used to fixate the globe to the orbital periosteum [12, 13]. Traction sutures are used to keep the eye in passive adduction for a transient period to increase the e ect of surgery [14, 15]. These sutures are kept in place for 6 weeks. This is our method of choice in total third nerve palsy [3] (Figs. 15.3–15.5). The other methods are usually performed in secondary cases with a failure of a previous operation.

The major problems in total third nerve palsy are lateral rectus contracture that cannot be overcome by any methods, orbital fibrosis in long-standing cases, recurrence of exodeviation, and the more bothersome diplopia following a successful surgery that provides orthophoria in a very limited area.

Fig. 15.4 In the case with congenital third nerve palsy traction sutures are seen in upper and lower eyelid to keep the eye in adducted position [3]

15.2.2Incomplete Third Nerve Palsy

In incomplete third nerve palsy with a superior or inferior branch or isolated EOM involvement, the treatment should be planned depending upon the a ected EOM(s). Recess-resect or transposition with a recession or BTXA injection may be preferred. In isolated inferior oblique palsy, transposition of horizontal recti perfectly works without weakening the superior rectus muscle. Complete third nerve palsy may present with partial involvement

and in that case, the treatment should be modified depending upon the severity of the involvement of the EOM(s). As the goal is to enlarge the diplopia-free field, the sound eye may be operated where necessary. In that case, faden operation or recession of the yoke muscle in the sound eye may be used.

Summary for the Clinician

■The correct evaluation of a complete or incomplete third nerve palsy (to diagnose the number of a ected muscles) and assessment of a total or partial involvement (the residual function of the a ected muscles) are the pearls for an appropriate surgical planning.

■In complete third nerve palsy, superior oblique function may easily be overlooked. The pearl is to use slit lamp for a precise evaluation to see the tiny intorsion.

■In incomplete or partial third nerve palsy, the aim is to provide a functional diplopia-free area; however, in complete third nerve palsy, the aim is to fixate the a ected eye in primary position.

■Orbital fibrosis is the bad prognostic sign for any type of surgery. The pearl is to create surgically induced restriction that provides a mechanical pulling e ect. A temporary pulling by traction sutures is very e ective that allows the development of the scar tissue while the globe was fixated on adduction.