Patrick Gooi, MD, FRCSC and Ike K. Ahmed, MD, FRCSC
Cataract surgery in the setting of severe zonular weakness is challenging, high-risk surgery. Zonular weakness varies in etiology, ranging from trauma to genetic diseases such as Marfan syndrome (Figure 8-1) and Weill-Marchesani syndrome.1,2 Methods for intraocular lens (IOL) insertion in the setting of zonular weakness include capsular tension rings (CTR), modified capsular tension rings, lensectomy with scleral fixation of a posterior chamber IOL (PCIOL), and placement of an anterior chamber IOL (ACIOL).3–5 The capsular tension segment (CTS), designed by Ahmed in 2002, provides intraoperative capsular support during surgery as well as continued centration of the IOL postoperatively. Using an endocapsular support device such as the CTS allows for phacoemulsification with placement of a PCIOL in the capsular bag. Placement of the PCIOL in the bag reduces the risk of chafing of uveal structures by the IOL edge, thus reducing the incidence of uveitis-glaucoma-hyphema (UGH) syndrome. There is theoretically less risk of damage to the corneal endothelium and trabecular meshwork with a PCIOL compared to an ACIOL. This chapter will describe the implantation technique for CTSs in cataract surgery.
The CTS is a 120-degree ring segment constructed of polymethylmethacrylate with a radius of 5 mm. A central, anteriorly placed eyelet hooks around the capsulorrhexis edge and is positioned anterior to the surface of the peripheral anterior capsule. The CTS may be atraumatically inserted prior to phacoemulsification. Prior to permanent scleral suture fixation of the CTS, it may be stabilized with an iris hook through the anterior eyelet to provide intraoperative capsular support. The anterior eyelet also allows for scleral suture fixation providing lasting capsular stability. Multiple CTSs may be used depending on the extent of zonular instability. CTSs provide tension in the transverse plane and therefore can be used in conjunction with a CTR, which provides circumferential support around the equator of the capsular bag.5 Placement of the CTS in the bag prevents the device from interacting with the corneal endothelium and angle structures.
Preoperative Considerations
The ideal first case should not have vitreous in the anterior chamber. During the initial learning curve, we recommend scheduling 2 hours of surgical time for a CTS case. With time, CTS cases can be completed within an hour. General anesthesia or a retrobulbar block is also advisable.
AVOIDING VITREOUS AND A VITRECTOMY
Combining the case with vitrectomy considerably increases the surgical challenge. To avoid a vitrectomy, a dispersive ophthalmic viscosurgical device (OVD) is applied to the area of zonulodialysis to keep the vitreous compartmentalized. Cohesive OVD is then instilled to maintain the anterior chamber depth. Shallowing of the anterior chamber is prevented at all costs, because this will encourage vitreous to migrate forward. Injecting balanced salt solution (BSS) on a 27-gauge cannula into the anterior chamber during instrument exchanges prevents anterior chamber shallowing and vitreous prolapse. Alternatively, OVD can be injected if it is to be used in the following step.
Figure 8-1. Intraoperative photograph of a dislocated crystalline lens in a patient with Marfan syndrome.
Figure 8-2. Intraoperative photograph showing the scleral groove where the CTS will be sutured to the sclera.
Figure 8-3. Intraoperative photograph showing the “knife and fork” configuration of paracentesis, as well as the main incision.
OPTIMIZING CORNEAL CLARITY
Cases with subluxated lenses require more time than a regular cataract surgery, especially if the case is combined with iris reconstruction and/or glaucoma surgery. Maintaining a clear cornea throughout the case for optimal visibility is paramount. This can be achieved by coating the corneal epithelium with dispersive OVD or with sterile preparations of hydroxypropyl methylcellulose. Corneal clarity is especially important when planning for a concurrent microinvasive glaucoma surgery procedure.
Surgical Technique
The complete surgical technique is outlined here and in Video 8-1.6
PERITOMY AND INCISIONS
A 4 clock hour peritomy is centered on the intended site for scleral suture fixation of the CTS. Subconjunctival local anesthetic is infiltrated in this area. After cautery, a 3-mm scleral groove is fashioned following the curvature of the limbus. It is positioned 1 mm posterior to the anatomical scleral spur (Figure 8-2).
Two paracenteses are made in a “knife and fork” fashion (Figure 8-3); these must be able to accommodate 23-gauge microtyers and iris microforceps. Short, narrow, and steeper paracenteses are made for iris hook placement.
STABILIZING THE ANTERIOR CHAMBER WITH OPHTHALMIC VISCOSURGICAL DEVICE/IRIS HOOKS/CAPSULORRHEXIS
Injecting dispersive OVD around the zonulodialysis prevents anterior vitreous prolapse. Additional dispersive OVD coats the endothelium, followed by cohesive OVD to maintain the anterior chamber in a soft-shell technique.7 The anterior capsule is often stained with trypan blue prior to initiation of the capsulorrhexis. Do not inject trypan blue freely into the anterior chamber, as this may diffuse posteriorly through the zonules to obliterate the red reflex. When initiating the capsulorrhexis, a 27-gauge needle may be required to puncture the capsule, or one can use iris microforceps on the anterior capsule to provide countertraction. Iris hooks may be placed on the rhexis edge in areas of the dialysis to stabilize the capsule, but it is important to release the hooks prior to finishing the capsulorrhexis in order to avoid creating a radial tear.
INSERTION OF CAPSULAR TENSION SEGMENT
The space for the CTS is prepared by placing the iris hooks on the capsulorrhexis edge to “tent up” on the capsule (Figure 8-4). Next, cohesive OVD viscodissects a local area to create a pocket for the CTS (Figure 8-5). Avoid disturbing the cortex during these maneuvers. One iris hook is positioned along the same meridian of the intended scleral suture for the CTS. Position the iris hook with the opening facing anteriorly to engage the eyelet of the CTS during phacoemulsification.
Figure 8-4. Intraoperative photograph of iris hooks used to “tent up” on the capsule to make space to receive the CTS.
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