The Capsular Bag Is Unexpectedly Mobile During Phaco. When Should I Implant a Capsular Tension Ring and Which Size Should I Use?
The best management approach to weak zonules during phaco is aimed toward maintaining a small-incision closed system, avoiding vitreous prolapse, preventing further iatrogenic zonular damage, and maintaining the integrity of the capsular bag for in-the-bag posterior chamber intraocular lens (PCIOL) implantation.
The first decision is to determine whether the case can continue with a modified phaco technique and adjunctive devices or whether the capsulo-zonular apparatus is so severely compromised that one needs to convert to an extracapsular cataract extraction (ECCE) with or without a pars plana posterior-assisted levitation (PAL) technique. I reserve this only for the most profound cases of zonular instability or if there is a capsular tear present.
In most cases, phaco can be safely continued with the use of any one or combination of the following devices: iris/capsular retractors (Figure 29-1), the capsular tension segment (CTS) (not approved by the US Food and Drug Administration) (Figure 29-2), the capsular tension ring (CTR) (Figure 29-3), or the modified CTR (M-CTR) (Figure 29-4). It is important to understand that the roles of these devices are 2-fold: they provide intraoperative support for phaco and they provide long-term postoperative support for an endocapsular PCIOL.
Figure 29-1. Iris retractors placed at the capsulorrhexis edge to support localized area of zonular weakness
Figure 29-2. The capsular tension segment (CTS).
Figure 29-3. The capsular tension ring (CTR).
Figure 29-4. The modified capsular tension ring (M-CTR).
Iris retractors, which have been designed to open a small pupil, or capsular retractors, which are modified for capsular placement, can be of immense use during these weak zonular cases. Every operating room should have these devices available for emergency situations. I find that iris retractors work fine for this purpose, although many surgeons have also used the specially designed capsular retractors. The iris/capsular retractors are placed on the capsulorrhexis edge to support the anterior capsule and center the capsular bag. As many retractors as required are used to support the area(s) of zonular weakness. They act as “synthetic zonules” that can be placed at any time during the procedure and are particularly useful during completion of the continuous curvilinear capsulorrhexis (CCC). The downsides of these devices include the potential for creating an anterior capsule tear at the point of contact and the possibility of the hooks becoming dislodged during the procedure. In addition, these retractors do not expand the capsular equator. This can lead to great difficulty during phaco and during cortical stripping and may fail to prevent aspiration of a lax capsule.
The CTR does an excellent job of expanding the capsular equator; however, it can be tricky to insert (see below). In cases of mild zonular weakness, the CTR alone is sufficient to stabilize the capsular bag; however, CTRs will not recenter or support the bag in cases of moderate or severe zonular instability. In these more advanced cases, sutured devices should be used.
The CTS can provide the dual benefits of a CTR and capsule retractors and can be easily placed with the capsular bag at any time during the case (Figure 29-5). To fixate the CTS to the sclera during surgery, an iris retractor is placed through the fixation eyelet.
Figure 29-5. CTS in positioned support by inverted iris retractor.
For me, the selection and the timing of device placement depends primarily on 2 factors. The first is the degree of focal zonulopathy, which is quantified according to the number of clock hours of zonular dialysis and/or a qualitative assessment of generalized zonular weakness (eg, any phacodonesis?). The second factor is the density of the cataract. I simply grade the zonulopathy as being either minimal, mild, moderate, or severe (Table 29-1).
I use a CTR in all cases with any zonular instability, unless there is an anterior or posterior capsular tear or discontinuity. I use a larger size ring (ie, 13 mm) in most cases because this provides greater centrifugal force and ensures adequate overlap of the end terminals.
The main question with CTRs is one of timing, and this will depend on the lens density. The CTR can be placed anytime after completion of the capsulorrhexis and should be inserted as early as is necessary. CTR placement prior to phaco can be accomplished safely in softer and medium density cataracts. One key suggestion in placing a CTR before phaco is to perform viscodissection rather than hydrodissection of the nucleus. Using a cohesive ophthalmic viscosurgical device (OVD) will cleave the cortical-capsular attachments, create space for CTR implantation, and provide enough lubrication to facilitate dialing the CTR into position.
In contrast, with a very dense lens, one needs to weigh the risks and benefits of early versus late insertion because of the potential for the CTR to tear the zonules or the capsule as it is implanted. This is because of the paucity of cortex and epinucleus with dense, bulky cataracts. In these cases, I try to delay implantation until the nucleus has been grooved and debulked so as to create more room within the bag for dialing the CTR into position. In order to delay CTR implantation for as long as possible, iris/capsular retractors or the CTS may be used to stabilize the capsular bag during phaco (discussed later).
CTR implantation may be performed either manually or with an injector (my preference). As it is implanted, the CTR should be directed toward the area of greatest zonular dehiscence in order to stress the compromised areas as little as possible. A Kuglen or similar hook can provide counter-traction if needed. In cases of advanced zonular weakness, the presence of iris/capsular retractors or the CTS can stabilize the capsular bag against the torque generated as the CTR is inserted.
For eyes with weak zonules, I do not alter my incision in order to preserve the advantages of a temporal clear cornea approach. If the zonular dialysis is temporal, I place the appropriate device needed to support this area beneath the incision.
In terms of OVD, I prefer a soft-shell technique. A dispersive OVD is used to coat the corneal endothelium and to cover the area of zonular dialysis, while a central cohesive core stabilizes the anterior chamber (AC). In the most severe cases, extra syringes of OVD will probably be necessary. As nuclear emulsification is nearing completion, placing Healon 5 (Advanced Medical Optics, Santa Ana, Calif) within the capsular bag can prevent the tendency for the capsular bag to collapse inward.
The advantages of a capsulorrhexis are well known, but this is even more critical in these cases. The capsulorrhexis ideally should be centered, round, and 5 mm in diameter. This size is large enough to facilitate lens removal and to prevent postoperative capsular phimosis and is also adequately sized for placement of iris/capsular retractors or a CTS. This diameter opening also permits continuous edge overlap of the intraocular lens (IOL) optic.
In cases of moderate to severe zonulopathy, it is important to stabilize the capsular bag with the appropriate device prior to phaco; otherwise, there is increased risk of vitreous prolapse, loss of nuclear fragments, or posterior capsular rupture.
In terms of phaco technique, if the lens is soft with a healthy cornea and a deep AC, I prefer to flip the nucleus and perform supracapsular phaco. If the circumstances are not appropriate for a phaco flip technique, an endocapsular vertical phaco chop is preferred. It is helpful to lower the fluidics and slow down the procedure in these cases.
It is essential that there be no loss of AC during the procedure, particularly during instrument exchange (ie, after phaco or after cortical aspiration). If this should occur, there is a significant risk of vitreous prolapse through/around the weak zonule. Balanced salt solution (BSS) or an OVD should be injected to prevent loss of AC at these times.
If vitreous prolapse is present preoperatively or occurs intraoperatively, a vitrectomy (either bimanual through limbal paracentesis incisions or pars plana with AC infusion as indicated) should be performed prior to continuation of phaco. However, the vitrectomy should not be initiated until after the capsular bag has been adequately supported and stabilized with the appropriate device. This avoids the potential for posterior dislocation of the nucleus during the vitrectomy.
Device Selection Guidelines
In these cases, a simple CTR is sufficient and this may be implanted either early on or at the end of the procedure. Because the zonules are only minimally affected, simply employing a phaco technique that minimizes zonular stress should alone suffice. The indication for the CTR is to provide postoperative IOL centration and support.
Again, a simple CTR is sufficient. In these cases, it is advantageous to place the CTR as early as possible. I sometimes like to have an iris/capsular retractor placed over the area of dialysis to stabilize this area and to provide counter-traction during CTR insertion. The retractors can either be left in until after IOL implantation or removed after CTR implantation. A sutured capsular tension device, such as the CTS or M-CTR, is usually not needed in these cases.
These cases do require a sutured device—either the CTS or M-CTR. I employ iris/capsular retractors while performing the CCC to re-center the capsular bag and to provide counter-traction. I then place a CTS over the area of zonular dialysis and place an iris retractor within the CTS to support the capsular bag in this quadrant. A CTR is then implanted after which phaco can be performed safely in a well-supported environment. The CTS can be permanently sutured to the sclera using 9-0 polypropylene. Alternatively, the M-CTR may be used; however, it is difficult to implant this device early in the case prior to phaco, and thus one must rely only on iris/capsular retractors until the lens has been evacuated.
The same principles apply as with moderate zonulopathy cases, but typically 2 CTS devices are required 180 degrees apart. Alternatively, the double-eyelet M-CTR may be used.
Intraocular Lens Selection and Placement
In-the-bag PCIOL placement is by far the ideal location. If the capsular bag has been well supported with a CTR with or without a sutured device (ie, CTS or M-CTR), this should be a stable environment in the long term. I prefer an acrylic PCIOL, which has less tendency for anterior capsular opacification and capsular contracture, which can lead to postoperative decentration.
Although it may be tempting to place a PCIOL in the sulcus in these cases, I generally avoid this. Unless the zonular deficiency is supported, sulcus IOLs are also at risk for postoperative decentration. Other alternatives, should an in-the-bag PCIOL be deemed risky, include an iris-sutured PCIOL, an iris-claw artisan aphakic IOL, or an AC IOL.
Postoperatively, one must carefully monitor the eye for capsular contracture. If this occurs, Nd:YAG laser anterior capsule relaxing incisions should be performed in order to release the tension and spread the contracting forces so as to avoid IOL decentration.
If postoperative IOL decentration does occur, the lens should be surgically repositioned as soon as possible. The presence of a CTR provides one with the option to pass a polypropylene suture loop under and over the CTR (needle passed through the bag to get under the CTR) so that the CTR becomes fixated to the sclera. Typically 1, 2, or even 3 fixation points may be required.
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