asthenopia or improve a squint. In purely accommodative strabismus, bifocals or progressive lenses must be considered. Fourth, for smaller, not too incomitant squint angles, the option of deÞnitive prismatic correction should be discussed before suggesting surgery. Fifth, when there is a high risk for anesthesia, strabismus surgery may not be indicated. For example, permanent occlusion of one eye should be considered for diplopia, which can only be treated surgically. For occlusion with glasses, the best cosmetic solution is obtained using Bangerter graded foils. The least strong foil to eliminate diplopia should be chosen, as it allows the best possible view of the occluded eye. In younger patients, usually foils are not be accepted and, therefore, occlusive contact lenses should be tried. Sometimes high myopic or hyperopic contact lenses induce enough blur to eliminate diplopia. The blurring contact lens solution is better compared to total occlusion as peripheral vision is preserved. Sixth, the surgical procedures that are going to be used should be read critically, especially regarding the time point when it is indicated. Is there evidence that very early surgery, for example for intermittent exotropia, has a better outcome than waiting for progression? Could it be that some patients operated on very early would never have required surgery? Unfortunately, many questions about strabismus surgery remain unanswered because of lack of randomized prospective studies and of long follow-up times. Sometimes good history taking will disclose that strabismus surgery is indicated, although the patient claims to be treated adequately, for example, with prisms. Only if asked speciÞcally about dangerous situations, an old patient wearing prisms may admit that he has already fallen several times from the stairs because of diplopia on downgaze when looking outside the glasses. If all nonsurgical options have been considered, strabismus surgery should be recommended, as this will prevent serious injuries.

6.3Types and Classification of Conjunctival Openings

The type of conjunctival incision will greatly inßuence the postoperative quality of life, cosmesis and, later, the function of the operated muscle. It will also inßuence the ease with which revision surgery. A certain type of conjunctival opening can be classiÞed by the

shape, orientation, size, and placement. Surgery may require one or several identical incisions or several different cuts. The shape is best described using capital letters, if necessary a combination of several. Single shapes used for strabismus surgery include C-shaped, I-shaped, and L-shaped openings (Fig. 6.1a). Combined shapes are CI-shaped and ICI-shaped cuts (Fig. 6.1b). The main orientations can be described as limbus-par- allel, radial, or oblique (Fig. 6.1c). The size can be given in millimeters or for a limbal peritomy in the quadrants involved or, alternatively, in clock hours. Placements may be limbal, paralimbal, or in the fornix. Usually, a fornix opening is well anterior to the true anatomical fornix. Additional placement information such as clock position or between or over which structures (muscle, muscle insertion) is necessary (Fig. 6.1d).

6.4 Rectus Muscle Procedures

Many strabismologists use HarmsÕ limbal approach [4], popularized by von Noorden [27, 28]. It is an ICI-shaped limbal opening over a quadrant allowing good performance of a muscle recession, resection or plication (Fig. 6.1e). The opening can be started either radially or perilimbally. For small muscle displacements, especially in younger patients with elastic conjunctiva, it is possible to reduce the total opening size by performing only one radial incision (Fig. 6.1f). Unfortunately, perilimbal openings may predispose a patient to anterior segment ischemia [8] and induce considerable postoperative discomfort, and are prone to complications like corneal dellen formation [25] and TenonÕs tissue prolapse [20]. Therefore, if possible, this approach should be avoided. For the rectus muscle, Swan suggested an I-shaped lim- bus-parallel incision close to the fornix, followed by a radial incision of the TenonÕs capsule over the bulk of the muscle (Fig. 6.1g) [24]. After muscle surgery, the TenonÕs capsule and conjunctiva have to be closed separately. This opening does not have the disadvantages of HarmsÕ limbal approach. However, today, it is rarely used because inadvertent injury to the muscle belly and ciliary vessels may occur [21]. This may induce copious bleeding. Postoperatively, it may induce visible scarring in the palpebral Þssure. Excessive scarring around the muscle often renders reoperations more difÞcult [1]. Parks advocated a nearly limbus-parallel I-shaped

Fig. 6.1 ClassiÞcation of conjunctival openings for strabismus surgery: (a) Single shapes used for strabismus surgery, (b) combined shapes, (c) main orientations, (d) placement information. Most important types of conjunctival openings for strabismus surgery:

(e) Harms limbal approach, (f) HarmsÕ limbal opening with only one radial incision, (g) SwanÕs opening, (h) ParksÕ opening, (i) VelezÕs opening, (j) SantiagoÕs opening, (k) same opening with two relaxing cuts over a vertical rectus muscle, (l) GobinÕs openings

fornix incision for the conjunctiva and TenonÕs capsule between two adjacent rectus muscles [16]. For horizontal rectus muscles, the lower fornix is selected, unless the muscle has to be supraplaced (Fig. 6.1h). For muscle surgery, the opening is moved over the muscle adjacent to the one that has to be displaced. This technique is very elegant as it does not have the disadvantages of the two previous techniques. If two adjacent rectus muscles need surgery, one opening will sufÞce. Unfortunately, it cannot be used in older patients with inelastic conjunctiva since full visualization of the surgical procedure will induce a tear. Velez suggested a radial incision covered by the upper lid. For medial rectus surgery, the incision is made in the nasal superior quadrant, and for lateral rectus surgery in the temporal superior quadrant (Fig. 6.1i) [26]. The disadvantages are that the cut reaches the limbus and that an already slightly decreased conjunctival elasticity will not allow displacing the cut without tearing. Santiago tried a paralimbal approach with an opening placed halfway between the limbus and the muscle insertion (Fig. 6.1j) [22]. For horizontal muscles, the disadvantages include visible scarring in the palpebral Þssure and difÞcult muscle access in inelastic conjunctiva, especially if larger muscle displacements are necessary. The technique is more valuable for vertical rectus muscle surgery as the openings are covered by the lids. For vertical rectus muscles, two additional relaxing cuts will improve visualization of the operating site (Fig. 6.1k). For strabismus surgeries reducing tissue disruption, the term MISS (minimally invasive strabismus surgery) has been proposed [9, 11Ð14]. For rectus muscle loop recession, Gobin described the principle of access through two small radial openings, one along the superior and the other along the inferior margin of the rectus muscles (Fig. 6.1l) [3, 10]. These openings allow recessions and plications (tucks) to be performed even in older patients with inelastic conjunctiva, as all surgical steps can be done without moving the cuts. Postoperatively, such cuts will remain covered by the lids except from during upgaze and excessive lateral gaze. This access technique minimizes anatomical disruption. If necessary, the cuts can be joined at the limbus, which will help to perform surgery using the usual limbal approach. Focusing on minimally invasive techniques, ParksÕ fornix and MISS parainsertional access techniques are presented in detail. Plications are preferable to recessions because they are less disruptive and can be easily revised in the Þrst couple of days.

Additionally, PriglingerÕs Y-split recession is described as an alternative to posterior Þxation suture because this approach avoids retroequatorial suturing. Adjustable sutures may be valuable for unpredictable situations. In such patients, I personally prefer an intraoperative adjustment, which is feasible if surgery is performed with topical anesthesia. Clearly, this technique cannot be used for children. The disadvantages if a postoperative adjustment has to be performed are (1) the need for general anesthesia in younger children, (2) possible discomfort or pain if performed with topical anesthesia,

(3) difÞculties in predicting Þnal alignment in the early postoperative course, and (4) possible increased scarring of the conjunctiva and perimuscular tissue, which may leave visible conjunctival scars and make repeat surgery more difÞcult.

6.4.1 MISS Rectus Muscle Recession

The technique and results of MISS rectus muscle recessions have been published in a case control study [9]. It can be performed without assistance. Use of the operating microscope is advisable. After applying a limbal traction suture, the eyeball is rotated away from the Þeld of surgery (Fig. 6.2a). Direct contact of the traction suture, with the cornea must be avoided because of the risk of corneal erosion. Two small radial keyhole openings are performed, one along the superior and the other along the inferior rectus muscle margin (Fig. 6.2a). The anterior margin of the opening is at the level of the tendon insertion. The total size of the openings depend on the amount of muscle recession that has to be achieved. As a rule of thumb, the opening size should be 1 mm less than the amount of muscle displacement to be achieved. The minimal opening size is 2.5 mm. For example, a recession or plication of 4 mm can be performed through two 3-mm openings. Usually, for recessions of more than 5 mm, an opening of 2 mm less than the amount is sufÞcient. Patients with reduced elasticity of the conjunctival tissue require slightly larger cuts. With blunt Westcott scissors and using the two cuts for access, the episcleral tissue is separated from the muscle sheath and the sclera (Fig. 6.2b). After identifying the borders of the muscle, it is hooked. Next, a meticulous dissection of the check ligaments

Fig. 6.2 Schematic representation of the surgical steps for MISS rectus muscle recession and plication [9]: (a) Paraincisional cuts, (b) separation of episcleral tissue from the muscle sheath and the sclera, (c) after hooking the muscle, dissection of the check ligaments and intermuscular membrane, (d) for a recession two sutures are applied to the superior and inferior borders of the muscle tendon, (e) detachment of the tendon, (f) reattachment

after measurement of amount of recession, (g) for a plication two sutures are applied to the upper and lower borders of the muscle at a distance corresponding to the plication amount, (h) insertion of iris spatula, (i) plication, (j) after performing the recession or plication, two sutures are applied to each of the small cuts, (k) if a better visualization is necessary, the cuts can be prolonged anteriorly, or (l) be joined at the limbus.

and intermuscular membrane is performed (Fig. 6.2c). This dissection is performed 6Ð7 mm behind the insertion. The resulting tunnel allows the surgeon to perform rectus muscle displacements easily. To perform a recession, two sutures are applied to the superior and inferior borders of the muscle tendon, as close to the insertion as possible (Fig. 6.2d). Then, the tendon is detached using Wescott scissors (Fig. 6.2e). Usually, hemostasis is necessary afterwards. If prominent vessels are visible at the insertion site, it is advisable to cauterize them before detaching the tendon. After measuring the amount of recession, the tendon is reattached with two sutures to the sclera (Fig. 6.2f). The tendon has to be stretched to avoid the middle part of the muscle bowing backwards. The surgical procedure is ended by applying two sutures to

each of the two small cuts (Fig. 6.2j) and retrieving the traction suture. The eye is not patched. Figure 6.3 shows photographs on the Þrst postoperative day in a 10-year-old patient after 4.5 mm lateral rectus recession. At the same time the ipsilateral medial rectus muscle was plicated. In the primary position, only a minimal redness of the conjunctiva is visible (Fig. 6.3a). In adduction upgaze (Fig. 6.3b) and adduction downgaze (Fig. 6.3c) the keyhole openings become visible. This type of MISS openings minimize postoperative visibility of surgery and patient discomfort. At any time during surgery, the cuts can be prolonged anteriorly (Fig. 6.2k), and, if necessary, joined with a limbal cut (Fig. 6.2l). This can become necessary if excessive bleeding occurs, and cannot be stopped with cautering the small cuts.

Fig. 6.3 Photographs on the Þrst postoperative day after a 4.5-mm lateral rectus recession and 5.5 mm medial rectus plication in a 10-year-old patient: (a) In primary position, all cuts are covered by the eyelids , (b) In adduction upgaze and (c) in adduction downgaze, the keyhole openings for recession become visible, (d) in abduction upgaze and (e) in abduction downgaze, the small cuts for plication become visible

a

c

e

b

d