6.4.2 MISS Rectus Muscle Plication

The MISS rectus muscle plication method has been reported in detail in the same publication that describes MISS rectus muscle recessions [9]. MISS rectus muscle plications are best performed under the operating microscope. There is no need for an assistant. A limbal traction suture is applied and the eyeball is rotated away from the Þeld of surgery (Fig. 6.2a). Two small radial conjunctival 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 plication. As a rule of thumb, the opening size will be at least 2.5 mm. For larger plication the opening should be 2 mm less than the amount of muscle displacement that has to be achieved. For example, a plication of 6 mm can be performed through two 4-mm openings. The openings for plications can be kept smaller compared to the ones for recessions of the same amount. The reason for this is that using forceps the location where the muscle has to be sutured can be advanced until it becomes visible through the keyhole opening. With blunt Wescott scissors 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 and intermuscular membrane is performed (Fig. 6.2c). This dissection is performed 6Ð7 mm behind to the insertion. The resulting tunnel allows the surgeon to perform a rectus muscle plication easily. If prominent vessels are visible at the insertion site or where the muscle suture will be applied, they should be cauterized before suturing. Two sutures are applied to the upper and lower borders of the muscle at the distance from the tendon insertion site corresponding to the plication amount (Fig. 6.2g). Next, the sutures are passed at the superior and inferior tendon insertions. An iris spatula is inserted between the tendon and the sutures (Fig. 6.2h) and the muscle is plicated as for open strabismus surgery (Fig. 6.2i). After removal of the spatulum, the surgical procedure is completed by applying two sutures to each of the two keyhole cuts (Fig. 6.2j). The eye is not patched. Figure 6.3 shows a 10-year-old patient on the Þrst postoperative day after 4mm medial rectus plication. The patient had at the same time an ipsilateral lateral rectus muscle recession. In the primary position, only a minimal redness of the conjunctiva is visible (Fig. 6.3a). In abduction upgaze (Fig. 6.3d) and

abduction downgaze (Fig. 6.3e) the keyhole opening becomes visible. MISS openings lying far away from the limbus reduce postoperative visibility of surgery and increase the quality of life in the immediate postoperative period. If necessary, the parainsertional cuts can be prolonged anteriorly (Fig. 6.2k), or joined with a limbal cut (Fig. 6.2l), which will allow better visualization of the operating site.

6.4.3 Parks’ Rectus Muscle Recession

Parks popularized a fornix-based conjunctival incision, which is covered by the lids postoperatively [16]. The opening is placed between two adjacent rectus muscles and can be made in any of the oblique quadrants. The cut direction is parallel to the limbus (Fig. 6.4a) or more oblique (Fig. 6.4b). The term fornix is misleading as such openings lie much more anterior than the anatomical fornix. The opening lies about 8Ð10mm behind the limbus. For larger surgical amounts, it will be necessary to use a cut lying closer to the rectus muscle and more posterior. Incisions in the lower quadrants are preferable as they will minimize visible postoperative redness. After applying a traction suture and incising the conjunctiva and TenonÕs capsule over a length of approximately 9mm (Fig. 6.4a or b), the rectus muscle is hooked using a small muscle hook (Fig. 6.4c). After ensuring that the muscle insertion has been found, the small hook is replaced by a larger one (Fig. 6.4d). If the end of the hook is visible through the conjunctiva, the complete insertion has been hooked. With a small hook the conjunctiva is retracted over the insertion (Fig. 6.4e). Using scissors the bare sclera is exposed (Fig. 6.4f). After applying two sutures to the muscle insertion (Fig. 6.4g), the muscle is desinserted, recessed and reattached to the sclera using two sutures. Some surgeons omit conjunctival closure in younger patients if at the end of surgery the conjunctival borders are closely approximated. Others prefer to apply sutures in all cases (Fig. 6.4l) [1].

6.4.4 Parks’ Rectus Muscle Plication

The incision is performed in the same way as described in the previous paragraph for rectus muscle recessions (Fig. 6.4aÐf). After exposing the muscle, two sutures are applied at a distance from the tendon insertion site

Fig. 6.4 Schematic representation of the surgical steps for ParksÕ rectus muscle recession and plication : (a, b) Fornix-based conjunctival incisions with slightly different orientations, (c) hooking of the rectus muscle with a small hook, (d) replacement of the small hook by a larger one, (e) retraction of the conjunctiva over the insertion, (f) exposure of bare sclera, (g) for a recession, two

sutures are applied to the muscle insertion, (h) muscle desinsertion and reattachment at the new location, (i) for a plication, two sutures are applied at a distance from the tendon insertion site corresponding to the plication amount, (k) after anchoring the suture at the original insertion site, an iris spatula is inserted, and (k) the muscle is plicated, (l) closure of the conjunctival incision

corresponding to the plication amount (Fig. 6.4i). Then, the two sutures are anchored to the sclera at the original insertion site. An iris spatula is inserted between the tendon and the sutures (Fig. 6.4j) and the muscle is plicated (Fig. 6.4k). Some surgeons do not suture the conjunctiva in younger patients if a spontaneous close approximation is visible. Others always apply sutures (Fig. 6.4l) [1].

6.4.5MISS Rectus Muscle Posterior Fixation Suture

Posterior anchoring of a rectus muscle is indicated for incomitant strabismus to reduce the force in the agonist contralateral to the weak muscle, to correct near/ distance incomitance, to reduce dissociated vertical deviation, or to decrease the amplitude of nystagmus. The MISS technique and its results of a case series have been published previously [14]. The surgical procedure is easier if done with the operating microscope and can be performed by oneself without the need

for an assistant. A limbal traction suture is applied to expose the rectus muscles, which have to be weakened. Contact of the traction suture with the cornea has to be avoided. For access, two small L-shaped cuts are performed slightly anterior to the location where the scleromuscular sutures will be placed (Fig. 6.5a). The size of the radial cuts is 4 mm and the relaxing cuts 2 mm. In patients with reduced elasticity of the conjunctival tissue, larger openings will be necessary to avoid conjunctival tearing. Anterior prolongation of the cuts will allow combining retroequatorial suturing with a MISS recession or plication. Here, isolated posterior Þxation suturing is shown. With blunt Westcott scissors the episcleral tissue is separated from the muscle sheath and the sclera. Then, a measure caliper is used to determine the exact placement of the scleromuscular sutures (Fig. 6.5a). The posterior Þxation is done by Þrst passing a nonresorbable suture through the sclera (Fig. 6.5b), followed by the muscle suture, which will include one third of the muscle (Fig. 6.5c). Tightening is performed by a three-throw adaptation suture followed

Fig. 6.5 Schematic representation of the surgical steps for MISS rectus muscle posterior Þxation suture [14] : (a) After two small L-shaped cuts are performed slightly anterior to the location where the scleromuscular sutures will be placed, a measure caliper is used to determine the exact placement of the scleromuscular sutures, (b)

a nonresorbable suture is passed through the sclera, (c) the muscle suture, which will include one third of the muscle, is performed (d) tightening is done by a three-throw adaptation suture followed by two securing loops, (e) afterwards, a posterior Þ xation suture is placed at the other border of the muscle, (f) conjunctival closure

by two securing loops (Fig. 6.5d). Afterwards, using the identical technique, a posterior Þxation suture is placed at the other border of the muscle (Fig. 6.5e). If necessary, hemostasis is performed. The surgical procedure is ended by applying single sutures (Fig. 6.5f). As both cuts lie far away from the limbus, eye patching is not necessary. If needed, anterior prolongation of the radial openings and/or the relaxing cuts will help to better visualize the operating site. This may become necessary in patients with excessive scarring from previous surgery, if a stronger hemorrhage occurs, or if the rectus muscle needs additionally to be recessed or plicated. Joining of the two cuts at the limbus will help to achieve full visualization of the operating site. Figure 6.6 shows the postoperative photographs at 24 h of a 27-year-old patient necessitating inferior rectus posterior Þxation surgery 14 mm behind the muscle insertion. In primary position, the cuts were fully covered by the lids and the perilimbal conjunctiva showed only a minimal redness. On upgaze, the keyhole openings became visible (Fig. 6.6, black arrow).

6.4.6Priglinger’s Rectus Muscle Y-Split Recession

Based on simpliÞed mechanical considerations, Priglinger et al. developed a new surgical procedure named Y-split recession allowing the reduction of the torque of rectus muscles [5, 6]. Surgery is usually performed on both rectus muscles. As there is no need for

retroequatorial suturing, the risk of retinal detachment is minimized and, probably, postoperative swelling and discomfort are also reduced. Torque reduction is achieved by splitting the rectus muscle over a length of 15Ð17 mm (Fig. 6.7a), desinsertion of the two halves after applying a suture to each muscle half (Fig. 6.7b), and Y-reinsertion (Fig. 6.7c). The splitting reduces the lever arm for all eye positions, which allows reducing the variability of the strabismus angle. The recession inßuences the minimum strabismus angle and allows controlling the position of the eye in primary position. Compared to retroequatorial myopexia, undesired radial forces will be minimal, and possibly proprioceptive inputs are preserved better. Force reduction in the direction of the operated rectus muscle is less pronounced compared to retroequatorial Þxation surgery. An increase in force reduction can be achieved by splitting the muscle up to 20mm behind the insertion and/or by increasing the Y-angle. Two different points have to be marked to determine the new insertion site of the two split muscle halves (Fig. 6.7d). The distances have been determined for a globe length of 21.2mm and a splitting distance of 15mm. Point A is located in the middle of the physiologic insertion of the muscle while point B is 6mm backwards. The reinsertion site lies x mm away from point B and y mm from point A. The distance z, the shortest distance between the new insertion and the cornea, will ensure that reinsertion is performed at the correct position. Therefore, this distance has also been named Òcontrol distance.Ó The different distances in function of the squint angle are as follows. For minimal angles up to 17pdpt. x = 8.5mm, y = 8.0mm, and z = 10.3mm, for minimal angles between 18 and 26pdpt. x = 9.0mm, y = 8.0mm, and z = 10.7mm, and for minimal angles above 27pdpt. x = 10.0mm, y = 8.0mm, and z = 10.8mm. Y-split recession has to be combined with ipsilateral rectus muscle reinforcement (resection or plication) for minimal strabismus angles of more than 23¡. Y-split recession can also be performed with the MISS technique using two paraincisional cuts. It usually induces more subconjunctival hemorrhage than a MISS recession alone and, therefore, mild perilimbal redness may be seen after surgery (Fig. 6.8).

6.4.7 MISS Rectus Muscle Repeat Surgery

Fig. 6.7 Schematic representation of the surgical steps for PriglingerÕs Y-split rectus muscle recession: (a) Splitting of the rectus muscle over a length of 15 -17 mm, (b) desinsertion of the two halves after applying a suture to each muscle half, (c) Y-reinsertion, (d) points used to determine the new insertion site of the two muscle halves

Fig. 6.8 20 Twenty-year-old patient on the Þrst postoperative day after MISS Y-split recession of the medial rectus muscle

the location of the rectus muscle insertion may differ from the physiologic position. Preoperative knowledge of where the exact insertion lies is less important for surgery using HarmsÕ limbal opening or ParksÕ fornix

incision, as the insertion position will not inßuence the location of the conjunctival cuts. However, this knowledge will allow minimizing of the MISS keyhole opening by placing it exactly where surgery will be done (Fig. 6.9a). Preoperatively, the planned intraoperative opening placement can be determined using information about the type and amount of previous surgery. If not available, the site can be established either preoperatively by location of the muscle insertion using the slit-lamp or intraoperatively by moving the eye, using the traction suture. Apart from eyes with excessive scarring or with abundant TenonÕs tissue, a movement of the eye frequently helps to distinguish the vessels that are conjunctival and those which belong to the muscle, thus helping to determine the actual insertion site. The big advantage of this approach is that the surgeon will not have to reopen an already traumatized perilimbal conjunctiva and, thus, can avoid the risk of a permanent increase of conjunctival redness and scarring. Probably, the risk of anterior segment ischemia is also decreased [8]. If previous surgery has been performed very carefully, the cuts will have to be

Fig. 6.9 Schematic representation of the surgical steps for MISS rectus muscle repeat surgery [11]: (a) For a repeat recession, two small parainsertional cuts are performed, (b) meticulous dissection of the check ligaments, the intermuscular membrane, and previous scars 6 -7 mm backward from the insertion, (c) two sutures are applied to the superior and inferior borders of the muscle tendon, (d) after measurement of the amount of recession, the tendon is reattached with the two sutures to the sclera, (e) for a repeat plication, two sutures are applied to the upper and lower borders of the muscle at a distance from the tendon insertion site corresponding to the plication amount, and the sutures are passed at the superior and inferior tendon insertions respectively, (f) an

iris spatula is inserted between the tendon and the sutures, and the muscle is plicated, (g) for an advancement after previous muscle recession, two small radial cuts are performed, one each along the actual superior and inferior muscle margins, (h) the episcleral tissue is separated from the muscle sheath and the sclera, (i) the muscle is hooked and a meticulous dissection of the check ligaments and intramuscular membrane is performed 6 -7 mm backward from the insertion, (j) two sutures are applied to the superior and inferior borders of the muscle insertion, (k) muscle desinsertion, (l) muscle anchoring after advancement, (m) conjunctival closure, (n) a better visualization is achieved by performing two L-shaped cuts; or (o) by joining the two cuts at the limbus

slightly larger compared to the eyes in which the rectus muscle had no prior surgery. For excessively scarred rectus muscles, for example, after retroequatorial Þxation sutures, adjustable sutures, or after several previous operations, an L-shaped keyhole opening will be necessary to adequately separate the muscle from the surrounding tissue (Fig. 6.9n). All surgical steps of repeat surgery can be performed without an assistant.

MISS rectus muscle recession: The principle of repeat rectus muscle recessions through keyhole openings does not differ from the previously described MISS rectus muscle recession techniques (see Sect. 6.4.1). Brießy, a limbal traction suture is applied to rotate the eyeball away from the Þeld of surgery and two small radial cuts are performed, one along the superior and one along the inferior muscle margin (Fig. 6.9a). As already mentioned, sometimes L-shaped openings will become necessary (Fig. 6.9n). With blunt Wescott scissors and using the two cuts for access, the episcleral tissue and previous scars are separated from the muscle sheath and the sclera. When the borders of the muscle have been identiÞed, the muscle is hooked. Now, a meticulous dissection of the check ligaments, the intermuscular membrane, and previous scars is performed 6Ð7 mm behind the insertion (Fig. 6.9b). Through the resulting tunnel, two sutures are applied to the superior

and inferior borders of the muscle tendon as close as possible to the insertion. After cauterization of visible vessels at the insertion, the tendon is detached using Wescott scissors (Fig. 6.9c). If necessary, additional hemostasis is performed. After measurement of the amount of recession, the tendon is reattached with two sutures to the sclera (Fig. 6.9d). The surgical procedure is Þnished by applying two sutures to each of the two small cuts (Fig. 6.9m). MISS rectus muscle plication: This technique is also comparable to the technique described for plications in eyes with no prior surgery (see Sect. 6.4.2). After moving the eye opposite to the Þeld of surgery using a limbal traction suture and performing two small cuts and a tunnel between the cuts, two sutures are applied to the upper and lower borders of the muscle at the distance from the tendon insertion site corresponding to the plication amount. Then, the sutures are passed at the superior and inferior tendon insertions respectively (Fig. 6.9e). Excessive scarring will make it necessary to prolong the openings more than usual. Compared to revision recession surgery, only rarely will an L-shaped opening become necessary (Fig. 6.9n). An iris spatula is inserted between the tendon and the sutures and the muscle is plicated (Fig. 6.9f). The surgical procedure ends with two sutures to both small cuts (Fig. 6.9m).

MISS rectus muscle advancement: This technique is different from all other MISS rectus muscle procedures and will, therefore, be described in more detail. After rotation of the eye using a limbal traction suture, two small radial cuts are performed, one along the superior and one along the inferior muscle margin (Fig. 6.9g). The anterior margin of the cut is at the level of the actual tendon insertion. With blunt Wescott scissors and using the two cuts for access, the episcleral tissue is separated from the muscle sheath and the sclera (Fig. 6.9h). When the borders of the muscle have been identiÞed, the muscle is hooked. Now, a meticulous dissection of the check ligaments and intermuscular membrane is performed 6Ð7 mm behind the insertion (Fig. 6.9i). The resulting tunnel allows the advancement to be performed. Two sutures are applied to the superior and inferior borders of the muscle tendon as close as possible to the insertion (Fig. 6.9j). Then the tendon is detached using Wescott scissors (Fig. 6.9k). If necessary, hemostasis is performed. After measuring

the amount of advancement, the tendon is reattached with two sutures to the sclera (Fig. 6.9l). To perform the reattachment without enlarging the opening, the cut has to be displaced anterior, using a forceps. The surgical procedure is completed by applying two sutures to each of the two small cuts (Fig. 6.9m). If a better visualization of the operating site is necessary, the two cuts can be prolonged anterior or posterior. In cases of excessive scarring, it is preferable to perform an additional perpendicular relaxing cut at the posterior border (Fig. 6.9n). If normal visibility is needed, e.g., if the muscle cannot be found, the two cuts can be joined at the limbus (Fig. 6.9o). Frequently, about 10 days after MISS repeat rectus muscle surgery, the eye will appear normal in primary position (Fig. 6.10a). In this 13-year- old patient, the medial rectus muscle was advanced by 5 mm and the lateral rectus muscle plicated by 5 mm because of consecutive esotropia. On eccentric gaze while retracting the eyelids, the keyhole openings will become apparent (Fig. 6.10bÐe).