Capsular tension rings (CTRs) are valuable tools for the cataract surgeon. These devices have enabled many patients with complicated cataracts to safely undergo successful small incision phacoemulsification with insertion of an IOL in the capsular bag. Prior to the advent of the
capsular tension ring, many of these cases would have required vitrectomy with an anterior chamber or sutured posterior chamber lens. But are CTRs just a short-term fix? Are we simply delaying the complication of subsequent dislocation? In some instances, I think we are.
The use of a CTR is indicated when there is not enough zonular support to successfully perform cataract surgery and/or place an endocapsular lens implant. Depending on the surgeon’s comfort level, the degree of zonular laxity or deficiency for which a CTR is used can be quite variable, ranging from a few clock hours to greater than 180 degrees. Various CTR designs exist (Morcher (FCI Ophthalmics), StabilEyes CTR (AMO), and ReFORM CTR (Alcon)) and some have extra eyelets that enable suture fixation to the sclera (Cionni CTR (FCI Ophthalmics)).
The rings do an excellent job of expanding, centering, and stabilizing the capsular bag. They also help to prevent capsular phimosis and opacification, and their efficacy has been demonstrated in numerous studies. CTRs are particularly successful for cases with less than 150 degrees of zonular instability. However, depending on the underlying etiology of the zonular compromise, there is a definite possibility that the remaining zonules may continue to weaken resulting in subluxation of the IOL/CTR/capsular bag complex, even if a ring with an eyelet has been sewn to the sclera at a single fixation point. In fact, spontaneous dislocation of the IOL/CTR/capsule complex has been reported in multiple patients. This scenario is most likely to occur in conditions such as pseudoexfoliation, syphilis, Marfan’s syndrome, and other forms of congenital ectopia lentis in which the pathology affects all of the zonules, as opposed to trauma (preexisting or intraoperative) in which the zonular defect is typically focal and the remaining zonules are normal. In the former situation, the CTR should be fixated to the sclera with more than one suture, and 9-0 rather than 10-0 is recommended to prevent late breakage, which has been reported in up to 10% of cases.
Will there be a future epidemic of dislocated IOL/CTRs? I certainly hope not, but I do fear that such scenarios may become more frequent, especially if surgeons continue to utilize CTRs in grossly unstable situations or in younger patients who have congenital zonular weakness and must live with these devices for decades. I believe that careful case selection is critical for preventing future dislocation. In questionable cases, an anterior chamber or sutured posterior chamber IOL should be used rather than making heroic attempts to place a lens in the bag, but if a CTR is used, then scleral suturing with at least two point fixation will ensure better stability of the capsule complex.
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