Figure 1. The crystalline lens has become subluxated secondary to spherophakia.
In a glaucoma practice, zonular weakness has a variety of causes, including congenital disorders, pseudoexfoliation syndrome, trauma, and even filtering surgery. Progressive conditions may require consideration for, not only immediate issues, but also the long-term stability of the capsular bag.
BE PREPARED
In addition to the most obvious signs of zonular instability (eg, irido- and/or phacodonesis, lens tilt, lens subluxation), a markedly shallow or hyper-deep anterior chamber may be a subtle clue. The ultrasound biomicroscopy has been an invaluable tool in preoperative zonular assessment and surgical preparation.
One must be prepared for vitreous management, which should be handled prior to lens extraction by means of a limited bimanual small-incision limbal or pars plana anterior vitrectomy. Both dispersive and cohesive viscoelastic agents can be very helpful for isolating tissue and creating space, respectively. We also believe that every surgeon's OR should have a stock of standard capsular tension rings (CTRs) now that they are available.
CTRs
Manufactured by Morcher GmbH (Stuttgart, Germany; distributed in the US by FCI Ophthalmics, Inc., Marshfield Hills, MA) and by Ophthec BV (Groningen, The Netherlands; distributed in the US by Advanced Medical Optics, Inc., Irvine, CA), CTRs come in three uncompressed sizes: 12.3, 13.0, and 14.3 mm. Made of PMMA, the CTR is a compressible circular filament with two smooth-edged end terminals designed to buttress and distribute tension to areas of zonular weakness and to expand the capsular equator (Figure 2).1 We recommend using the 13-mm device for most eyes, because it is desirable for the end termini to overlap each other to ensure an equal distribution of tension. CTRs can be inserted manually or via an injector, a method that greatly facilitates implantation. They should be dialed into the area of zonular weakness, if identifiable.
Figure 2. The standard CTR.
CTRs are indicated in cases of mild, generalized zonular weakness or small, localized zonular dialysis (3 to 4 clock hours). In these eyes, the devices provide excellent capsular support and improve capsular bag/in-the-bag PCIOL centration. It is important to remember, however, that the standard CTRs do not recenter an already significantly subluxated or dislocated lens. Such cases benefit from modified, scleral, sutured, capsular tension devices, as described later. Furthermore, CTRs should not be used in the presence of an anterior capsular tear, a discontinuous capsulorhexis, or a posterior capsular tear.
There is considerable controversy regarding the optimal time to implant a CTR, which may be inserted at any time after capsulorhexis and hydrodissection. Early implantation provides intraoperative support during phacoemulsification and cortical aspiration but also has some drawbacks. A study of CTR implantation using Miyake-Video analysis found that, in cases of moderate zonular dialysis and particularly of dense cataract, the insertion and dialing of a CTR places considerable stress on the capsular bag and existing zonules and may cause iatrogenic capsular and/or zonular damage.2 Furthermore, cortical removal can be extremely challenging when a CTR is in place. In cases of mild zonular weakness and/or a soft lens, the CTR may be implanted early with minimal trauma, but it may not be required for intraoperative support in these milder cases. It is critical to use viscodissection to create adequate space for implantation and cleave cortex from the capsular fornix in this situation. Surgeons should halt the implantation process if excess capsular-bag torque or displacement occurs.
IRIS/CAPSULAR RETRACTORS
If CTRs should be implanted after the capsular bag has been decompressed, what should surgeons use for intraoperative support? Iris retractors, employed in a modified fashion on the capsulorhexis' edge, can be helpful (Figure 3). These instruments act as synthetic zonules and can be inserted atraumatically. Iris retractors can be helpful during capsulorhexis creation for recentering a subluxated lens, and they provide useful countertraction. It is important to use multiple iris retractors as needed. Richard Mackool, MD, has designed modified capsular retractors (Cataract Support System; Duckworth & Kent Ltd., Hertfordshire, England) that are used in a similar fashion.
Figure 3. Using a flexible iris retractor at the capsule's edge during capsulorhexis provides necessary countertraction and stability (left). The iris retractors are located at the capsulorhexis' edge during phacoemulsification and cortical removal (right).
Under no- or very low-flow conditions (ie, when creating the capsulorhexis), iris/capsule retractors work well. During inflow and outflow in phacoemulsification, and particularly with a hard lens and/or substantial zonular weakness, however, the focal pressure on the anterior capsule may cause an anterior capsular tear. In some cases, the retractor may become dislodged.
CAPSULAR TENSION SEGMENT
The capsular tension segment (CTS; Morcher GmbH; not FDA-approved but available on a compassionate basis) was designed to provide early capsular support during phacoemulsification and to provide stability for more than just mild zonular weakness (Figure 4).2 This partial ring segment features a central fixation eyelet that acts as a hanger, propping up the capsule in areas of zonular instability. An iris retractor is placed upside down through this eyelet, which sits anterior to the anterior capsule, while the body of this implant sits in the capsular fornix (Figure 5). An advantage of the CTS is that it can be implanted with a no-dialing technique and thus results in minimal capsular/zonular trauma when placed early in the case (ie, prior to phacoemulsification). Unlike a solitary iris retractor, the CTS' broad support and size make anterior capsular tears and/or dislodgement unlikely. Therefore, the device can provide much needed support and security intraoperatively. It may also be used in the presence of an anterior or posterior capsular tear.
In addition, the CTS may be sutured to the sclera in cases of severe zonular weakness. The surgeon may place a single segment over an area of zonulysis or two implants 180º apart for global weakness. Because the CTS provides transverse support (ie, in the x and y axes), we often combine its use with that of a standard CTR in cases of global or diffuse weakness in order to provide circumferential support.
Figure 4. The CTS provides intraoperative support with the use of an iris retractor and postoperative, capsular-bag, scleral fixation with a polypropylene or GoreTex suture (W. L. Gore and Associates, Milpitas, CA).
Figure 5. The surgeon has placed the CTS within the capsular fornix in the area of zonular dialysis. An iris retractor and suture have been passed through the fixation eyelet for support (left). The CTS device provides secure and broad support of the capsular bag during phacoemulsification (right).
SUTURING DEVICES TO SCLERA
As stated, a standard CTR is not adequate in cases of more than mild zonular weakness or a dialysis greater than 3 clock hours. When progressive zonulysis is a concern, one must consider suture fixation of a capsular tension device. Although alternatives include intracapsular cataract extraction with placement of an ACIOL, a scleral-fixated PCIOL, or an iris-fixated PCIOL, we advocate placing a PCIOL in the bag by using either scleral fixation of the Cionni modified CTR3 (Morcher GmbH; not FDA-approved but available on a compassionate basis) (Figure 6) or one to two CTS devices (Figure 7). Because the modified CTR and the CTS devices feature an anteriorly positioned fixation eyelet for suture fixation, the suture need not pass through the capsular bag. If only a standard CTR is available, we would suggest suturing through the capsular bag by making anterior and posterior passes around the CTR to loop and secure it to the scleral wall.
Figure 6. The Cionni modified CTR for scleral fixation.
Figure 7. Two CTS devices have been secured with scleral suture fixation (left). The surgeon uses dual CTS devices within the capsular bag (right).
We prefer using an ab-externo technique to pass 9–0 polypropylene suture needles through a scleral groove 1.5 mm posterior to the limbus, in the area of greatest zonular weakness. If necessary, we suture two CTS devices 180º apart.4
SUMMARY
Capsular tension devices represent a major advance in the management of mild, moderate, and severe zonular weakness. Using CTRs and CTS devices in conjunction with a small-incision, closed-system technique minimizes the risk of vitreous prolapse, retains the value of the endocapsular placement of a PCIOL, and provides long-term centration of the lens implant. Due to concerns of iatrogenic capsular/zonular trauma, however, surgeons may wish to avoid whenever possible implanting a CTR prior to performing phacoemulsification. If zonular weakness necessitates intraoperative support, multiple iris retractors or, preferably, one or more CTS devices can provide capsular stability. After lens extraction, the surgeon may implant a CTR. A sutured CTS device is appropriate in cases of profound zonular dialysis.
Iqbal Ike K. Ahmed, MD, is Assistant Professor at the University of Toronto and Clinical Assistant Professor at the University of Utah in Salt Lake City. He stated that he holds no financial interest in the products and companies mentioned herein. Dr. Ahmed may be reached at (905) 820-3937; ike.ahmed@utoronto.ca.
Michael Butler, MD, is a medical trainee at the University of Calgary. He stated that he holds no financial interest in the products and companies mentioned herein.
1. Nagamato T, Bissen-Miyajima. A ring to support the capsular bag after continuous curvilinear capsulorhexis. J Cataract Refract Surg. 1994;20:417-420.
2. Ahmed IK, Kranemann C, Crandall AS. Capsular hemi-ring: next step in effective management of profound zonular dialysis. Film presented at: The ASCRS/ASOA Symposium on Cataract, IOL and Refractive Surgery; April 12 and 13, 2003; San Francisco, CA.
3. Cionni RJ, Osher RH. Management of profound zonular dialysis or weakness with a new endocapsular ring designed for scleral fixation. J Cataract Refract Surg. 1998;24:1299-1306.
4. Ahmed IK, Crandall AS. Ab externo scleral fixation of Cionni modified capsular tension ring. J Cataract Refract Surg. 2001;97:977-981.
