Ehsan Rahimy, MD
In the setting of inadequate capsular support, surgical options for intraocular lens (IOL) placement include (1) insertion of an anterior chamber IOL (ACIOL), (2) iris fixation of a posterior chamber IOL (PCIOL), and (3) scleral fixation (with or without suture) of a PCIOL. The choice of technique is often influenced by the patient’s age, anatomical considerations (eg, prior trauma with iris tissue loss), other ocular comorbidities (eg, glaucoma), and ultimately, surgeon preference and comfort level.
With respect to scleral-sutured IOLs, 2 different approaches have been described: an ab externo (outside-in) or ab interno (inside-out) techniques. In 2014, our institution described a modified ab externo method for 2-point scleral fixation of a CZ70BD (Alcon Laboratories, Inc) IOL using Gore-Tex (WL Gore & Associates), a nonabsorbable polytetrafluoroethylene (PTFE) monofilament suture (Figure 33-1).1 This procedure was adapted from an earlier description by Slade et al,2 and modified to include concurrent 23-gauge pars plana vitrectomy. While traditionally used in cardiac and vascular surgery, Gore-Tex has been gaining popularity in ophthalmology because the resilient PTFE material may be less prone to suture breakage than the commonly used polypropylene material (Prolene; Ethicon).3–5
With increasing use and experience, this technique has undergone further modification in recent years. Foremost among them is the currently preferred use of an Akreos AO60 IOL (Bausch + Lomb), with a 4-haptic design that enables excellent IOL centration and stabilization through 4-point fixation (Figure 33-2). Although any of the aforementioned strategies may be employed effectively in aphakia with poor capsular support, scleral fixation of an Akreos AO60 IOL with Gore-Tex suture has numerous potential advantages. These include relative ease of insertion and fixation through small corneal incisions, minimized IOL tilt, avoidance of iris contact, and a theoretically lower risk of lens dislocation postoperatively.
This chapter presents a brief overview of the salient steps of the procedure along with situational considerations and helpful tips for achieving the best surgical results.
Surgical Technique
The key steps to this procedure are outlined in Video 33-1. Beginning at the horizontal meridian, limited superonasal and inferotemporal 90-degree conjunctival limbal peritomies are created with relaxing radial incisions. External cautery is used to obtain adequate hemostasis. Next, a standard infusion line for pars plana vitrectomy is introduced (typically placed inferiorly or in the inferonasal quadrant away from the sclerotomies for suture fixation maneuvers).
A toric lens marker is then used to mark the corneal limbus at 2 points in the horizontal plane located 180 degrees apart at 3 and 9 o’clock. The 2 cannulas are then placed along this axis 3 mm posterior to the limbus. The introducer is then used to construct 2 additional sclerotomies: one 5 mm inferotemporal to the temporal cannula and the second 5 mm superonasal to the nasal cannula, while maintaining a 3-mm distance from the limbus (Figure 33-3A). Note that all scleral incisions are made with a straight, nontunneled entry while keeping the flat portion of the trocar blade parallel to the limbus. A standard pars plana vitrectomy can then be performed. This technique is compatible with 23-, 25-, or 27-gauge instrumentation. Use of smaller gauge instrumentation may reduce the incidence of postoperative wound leakage and potential hypotony, although the author has not encountered these problems while using any of these 3 platforms.
Figure 33-1. Gore-Tex, a nonabsorbable, PTFE monofilament suture with greater tensile strength than polypropylene.
The anterior chamber may next be entered either through a previously created clear corneal incision (if recent cataract extraction was performed) or by constructing a new incision through the superior cornea using a 2.75-mm phaco keratome blade. The internal lip of the scleral wound can be slightly enlarged to 3.5 to 4.0 mm. With the infusion clamped, the corneal endothelium is protected by injecting viscoelastic. If a dislocated IOL is concurrently present, it may now be explanted through the main wound.
Next, the CV-8 needles of the 8-0 Gore-Tex suture are amputated, and the suture is cut into 2 halves. Each suture end is then threaded through 2 adjacent eyelets of the Akreos AO60 lens at equal lengths for eventual 4-point fixation of the IOL inside the eye. To minimize the potential for iris chaffing, the suture is passed through the first eyelet in an anterior to posterior fashion, and then from posterior to anterior as it exits through the adjacent second eyelet. This pattern is repeated with the second half of suture on the contralateral side of the IOL. In a hand-to-hand or handshake technique, either the nasal or temporal 2 ends of the Gore-Tex suture are passed into the anterior chamber and pulled out of each corresponding sclerotomy using flat intraocular forceps (eg, Alcon MaxGrip forceps).
Figure 33-2. (A, B) Postoperative outcome demonstrating 4-point fixation of an Akreos AO60 IOL with an excellent cosmetic and functional result. Arrows indicate previous temporal sclerotomy sites with an externalized loop of Gore-Tex suture in between.
Figure 33-3. Two different schematics for placement of the conjunctival peritomies and sclerotomies when performing a Gore-Tex–sutured IOL procedure.
Figure 33-4. (A-C) Postoperative outcome demonstrating 4-point fixation of an Akreos AO60 IOL when the sclerotomy placement is rotated away from the nasal bridge. Arrows indicate placement of the sclerotomy sites with an externalized loop of Gore-Tex suture in between. The Akreos AO60 IOL can then be folded along its long axis using Kelman-McPherson or similar forceps and introduced into the anterior chamber. Once in the eye, the IOL is displaced into the posterior chamber, and under direct visualization, the trailing nasal/temporal 2 ends of the Gore-Tex suture can be grasped and externalized through the respective sclerotomies using intraocular forceps. All 4 ends of the Gore-Tex suture are then pulled and tension is balanced to ensure centration of the IOL optic. The trocars are then individually removed over the Gore-Tex sutures, which are tied using either a 3-1-1 or adjustable slip knot technique. The knots are trimmed and buried into the sclerotomies that previously housed the cannulas in order to minimize the chance for wound leak because these incisions tend to gape more. The viscoelastic is then irrigated out of the anterior chamber, and the corneal incision may be closed using a 10-0 nylon suture. The overlying conjunctival peritomy is then closed, making sure that the externalized loop of the Gore-Tex suture is completely covered. Troubleshooting Tips Beginning users unfamiliar with this technique may feel uncertainty regarding the execution of certain intraoperative steps, as well as whether and for whom this procedure should be used instead of traditional secondary IOL methods. The following points help address these concerns in order to optimize surgical outcomes. PREOPERATIVE CONJUNCTIVAL ASSESSMENT The relative ease, or difficulty, of handling the conjunctiva (especially closure at the end of the case) can make a significant difference in the overall case length as well as the surgeon’s perceived difficulty of the procedure. An important consideration is whether the patient has had previous ocular surgery involving conjunctival manipulation. Is there a history of prior surgery such as a scleral buckle, multiple vitrectomies, or a trabeculectomy or tube shunt? These are important not to overlook because patients who need a secondary IOL often have had prior surgery. Alternatives to an anterior chamber lens are preferable for patients with a prior retinal detachment repaired with a scleral buckle, pars plana vitrectomy, and lensectomy or patients with glaucoma and filtering blebs. These are not ideal cases for a surgeon’s initial attempts to use this technique. In limited cases where the conjunctiva was too friable to adequately cover the exposed loop of Gore-Tex, we have had success using Tutoplast (IOP Ophthalmics) as a scleral patch graft to cover the suture. INCISION PLANNING Based on certain anatomical considerations, one may consider rotating the placement of the conjunctival peritomies and sclerotomies in order to better facilitate subsequent intraocular maneuvers. Two different schemes have been popularized that are outlined in Figure 33-3. In situations where the cataract surgeon created a superior corneal incision, a superior approach where the 4 sclerotomies straddle the horizontal meridian (2 mm superior and inferior to the toric markings) with the cannulas housed in the superior sclerotomies may be preferred (see Figure 33-3B). Alternatively, a patient with a prominent nasal bridge may create difficulty for certain maneuvers with the intraocular forceps. In such instances, it may be more convenient for the surgeon to create the peritomies in the superonasal and inferotemporal quadrants. While the cannulas are still inserted 180 degrees apart in the horizontal meridian in line with the toric markings, the supplemental sclerotomies are created 4 mm superonasal to the nasal cannula and 4 mm inferotemporal to the temporal cannulas (see Figure 33-3A). This effectively shifts the axis of IOL fixation away from the nasal bridge, creating more operating access for the surgeon (Figure 33-4). Furthermore, when disposable intraocular forceps are being used (ie, Alcon MaxGrip forceps), the shaft is quite malleable and can be easily bent to assume a curvilinear configuration for easier manipulation when working through the nasal sclerotomies. DISTANCE FROM THE LIMBUS The decision to place the sclerotomies 2.0 or 3.0 mm from the limbus is at the surgeon’s discretion. Anecdotally, the author has observed that sclerotomy placement 2.0 mm posterior to the limbus can occasionally result in IOL contact with the posterior iris (diagnosed both intraoperatively using endoscopic visualization and postoperatively using ultrasound biomicroscopy). For this reason, most surgeons performing this technique have adjusted their sclerotomy placement to 3.0 mm posterior to the limbus. Accordingly, the desired IOL power becomes equivalent to that used for in-the-bag placement of the lens. If the surgeon elects to create sclerotomies 2.0 mm from the limbus, the IOL calculation should then be adjusted for a sulcus-placed lens (Figure 33-5). Figure 33-5. Adjustment of desired IOL power based on sclerotomy distance from the limbus.
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