Capsular tension rings (CTRs) are C-shaped devices used during cataract surgery to stabilize the lens capsule. Hara et al1 introduced this device in 1991, and in the years since, Nagamoto, Witschel, Cionni, and Ahmed have contributed with helpful modifications.2-5 These rings are used to increase the stability of the lens capsule during and after lens extraction and IOL implantation.
CTRs may be used in many conditions, including zonulolysis from trauma or previous surgery, mature cataracts, high myopia, and pseudoexfoliation. They may also be useful in disorders that influence the ciliary zonula, such as Marfan syndrome, Marchesani syndrome, scleroderma, homocysteinuria, spherophakia, porphyria, and hyperlysinemia. Furthermore, a CTR can be helpful in cases where exact IOL centration is needed after cataract surgery to achieve a satisfactory visual result, such as with multifocal and toric IOLs.
TIMING
The timing of CTR implantation varies depending on the individual clinical case. The objective is to place the CTR so that it provides the best stability of the lens capsule diaphragm. In some cases, the CTR should be placed immediately after the capsulorrhexis is made. In others, it is not needed until cortical removal or immediately before IOL insertion.
Bayraktar et al6 found that in eyes with pseudoexfoliation, placing the ring before phacoemulsification reduced zonular dialysis during the case and improved IOL fixation. Others have argued that the ideal timing is after lens extraction and decompression of the capsular bag.7 Early ring implantation has led to difficulty removing cortical material and was also found to increase capsular torque and displacement.7
A MODIFICATION: THE HCTR
The Henderson Capsular Tension Ring (HCTR; Morcher GmbH, Stuttgart, Germany; Figure 1) was created to address the challenge of cortical removal after implantation. Conventional CTRs often trap cortical material, making removal difficult and increasing overall surgical time. The structural design of the HCTR allows easier access to cortical material. Like other CTRs, the HCTR is a flexible, PMMA, C-shaped loop with two terminal eyelets. The main modifications of the HCTR are eight equally spaced 0.15-mm indentations that lie interspersed throughout the loop. After implantation of the HCTR, the areas under the indentations are accessible to cortical cleanup. This design allows easier cortical removal without sacrificing capsular stability, making the HCTR a valuable device for cases in which capsular stability is needed prior to complete lens removal.
A single-masked prospective study performed on pig eyes tested the efficacy of the HCTR against conventional CTRs. Pig eyes were randomized to implantation with one of three rings: Morcher 14C (Morcher GmbH), StabilEyes (Advanced Medical Optics, Inc., Santa Ana, California), or the HCTR. An unmasked surgeon implanted each CTR. After implantation, a surgeon masked to the CTR selection performed phacoemulsification and cortical removal. The CTRs were not visible to the masked surgeon during surgery because they were completely hidden by the iris flap. Surgeries in the pig eyes with HCTRs demonstrated the lowest mean surgical time, mean irrigating balanced salt solution volume, and effective phacoemulsification time, although not all of these differences were statistically significant (P=.06, .03, .34, respectively).
The HCTR maintains the benefit of distributing stress around the entire equatorial area of the lens capsule, and the indentations allow lens and cortex to be stripped and removed. Once the residual material has been removed, the HCTR can be rotated to change positions of the indentations and allow further removal of lens material that was compressed by the nonindented portions of the HCTR.
TECHNIQUE
Like other CTRs, the HCTR can be inserted manually or with an injector system. Modifications with suturing eyelets, such as the Cionni Capsular Tension Ring (Morcher GmbH) or Ahmed Capsular Tension Segment (Morcher GmbH), must be inserted manually. Before inserting any CTR, the capsular bag should be inflated with a dispersive viscoelastic solution. Dispersive viscoelastics such as chondroitin sulfate maintain capsular bag expansion while the CTR is manipulated. Cohesive viscoelastics made from sodium hyaluronate can be inadvertently extruded during implantation.
If possible, the CTR should initially be inserted into the area with the most zonular dialysis and rotated clockwise. The greatest amount of stress on the capsular bag is where the CTR is initially introduced. Hence, if the location of the initial implantation is at the weakest area, the CTR is pushed toward the weakness, thereby relaxing the remaining zonules; however, if the CTR is implanted 180? away from the area of weakness, the force of the implanted CTR pulls from the weakness, causing the remaining zonules to be strained.
Often the greatest difficulty of implanting any CTR is the final placement of its trailing end. With both manual and injector implantations, the final end must be carefully placed into the capsular bag. The difficulty of this step lies in releasing the hook of the injector system or manipulating the instrument from the final trailing eyelet. We recommend using a second instrument in the sideport incision to push off the trailing end of the CTR and assist in placing it into the capsular bag.
CONCLUSION
CTRs have proven to be useful devices for cataract surgery. During the years since their introduction, many modifications have been made to improve upon the original, the latest being the HCTR. Although CTRs can stabilize the eye for successful surgical completion, implantation of these rings should be carefully planned and properly executed. Additional improvements and information may further improve CTR performance and efficacy.
Kelly J. Grimes, MS, is a Research Associate at Ophthalmic Consultants of Boston. Mr. Grimes states that he has no financial interest in the products or companies mentioned. He may be reached at kellyjgrimes@gmail.com.
Bonnie An Henderson, MD, is a partner at Ophthalmic Consultants of Boston, and an Assistant Clinical Professor at Harvard Medical School, Boston. Dr. Henderson states that she is a paid consultant to Alcon Laboratories, Inc., and Ista Pharmaceuticals. She may be reached at tel: +1 781 487 2200, ext 3321; fax: +1 781 487 5717; bahenderson@eyeboston.com.
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