Surgical options expand for capsular tension rings

With new devices, safer insertion methods and increased postop advantages, capsular tension rings are attracting the attention of practitioners.

Capsular tension rings are proving to be useful for surgeons dealing with complicated cataract. The devices can stabilize the capsular bag in cases of posterior capsular tear or zonular dehiscence, allowing an IOL to be implanted in the bag when previously it might have been repositioned in the sulcus.

“Many surgeons dealing with complex, dislocated cataracts have found capsular tension rings to be very useful and innovative,” Ike K. Ahmed, MD, FRCSC, told Ocular Surgery News.

Capsular tension rings (CTRs) were designed to help stabilize the lens capsule during IOL implantation in the presence of weak or broken zonules. But it is also being found that the barrier effect of the ring sitting in the capsular fornix may help prevent lens epithelial cell migration.

“The tension ring provides expansion and stabilization of the periphery of the capsular bag. It is useful for weak zonules, pseudoexfoliation or mild subluxation,” Michael D. Olson, OD, PhD, said during a presentation at the American Society of Cataract and Refractive Surgeons meeting. CTRs have also been helpful in patients with high myopia, lens decentration, ocular trauma and excessive lens movement.

Surgeons are discovering the usefulness of the rings, and new devices such as capsular tension segments are being used for additional applications.

This article reviews some of the devices currently in clinical trials in the United States and others in use internationally. No capsular tension rings currently have regulatory approval for marketing in the United States.

Suture placement through fixation eyelet of CTS for scleral fixation over areas of zonular dialysis resulting in centration of capsular bag and intraocular lens implant. Note two CTS implants were used for fixation in this case. (All photos courtesy of Ike K. Ahmed, MD, FRCSC.)

StabilEyes ring holds promise

Interim results from the clinical investigation of Advanced Medical Optics/Ophtec’s endocapsular ring were presented during ASCRS. The endocapsular ring, to be marketed under the name StabilEyes, is a round tension ring used to stabilize the capsular bag in the presence of up to 33% broken zonules.

The ring is made of compression-molded PMMA, Dr. Olson said. It is available in a clear or brown 12-mm frame for corneal diameters of 12.75 mm or less, or a 13-mm frame for larger corneal diameters.

In a nonrandomized multicenter clinical trial, investigators implanted 210 endocapsular rings in 181 patients with weakened or broken zonules: 86% of eyes had weakened zonules and 14% had broken zonules, Dr. Olson said.

At 3 months after IOL and CTR implantation, 99% of the IOLs implanted were centered, Dr. Olson said. “From these data, we may conclude that the endocapsular ring performs well,” he said.

Reported complications included macular pucker, hyphema and loose lens. Few YAG capsulotomies were required within 6 months after surgery.

“The device does not appear to contribute to surgical complications. Surgeons should consider the endocapsular ring to be a positive adjunct to cataract surgery,” Dr. Olson said. Ophtec’s CTR has completed phase 3 Food and Drug Administration trials. Device approval is pending final review of data by the FDA.

Segments reduce trauma

A different type of capsular tension device is the capsular tension segment (CTS) from Morcher.

“The capsular tension segment is both an innovative device and implant for the management of profound zonular dialysis,” Dr. Ahmed said. “It can be atraumatically inserted and secured with an iris retractor for intraoperative support and suture fixation for postop capsular bag stability.”

Dr. Ahmed has implanted the CTS in 15 cases thus far. He has seen good postop results, with adequate posterior chamber IOL centration and a reduction of refractive cylinder and spherical equivalent in most patients, he said.

Significant zonular dialysis with subluxed crystalline lens.

During his presentation at the ASCRS meeting, Dr. Ahmed discussed the risks posed by CTRs.

“The insertion of a ring creates a certain amount of high-degree torque and tension on the existing zonules. This can potentially create further iatrogenic damage to the existing zonules, especially when placed prior to lens extraction,” he said.

The CTS provides an alternative to a full ring, working equally effectively in stabilizing the capsular bag but inducing minimal torque, Dr. Ahmed said. Because of its smaller size, the partial ring device — a 90° PMMA segment with a radius of 5 mm — avoids capsular tears and iatrogenic zonular trauma during phaco and cortical removal, he said.

“The segment is placed atraumatically, with minimal movement of the lens and certainly no trauma to the zonules. Miyake video studies have confirmed much less zonular stress with CTS insertion vs. ring implantation,” he said.

Most important, he added, is the flexibility of using the segment.

“The beauty of this implant is the ability to combine it with other implants,” he said.

Depending on the degree of instability, multiple segments may be used simultaneously to provide capsular support.

“These segments allow surgeons to customize their treatment, using segments in a flexible manner while reducing torque and inducing less zonular stress,” he added.

The CTS is in use in Dr. Ahmed’s clinic in Canada, but it is not currently being investigated in the United States, according to a Morcher spokesman. A Morcher CTR has completed FDA phase 3 testing, and data for premarket approval will soon be submitted to U.S. regulators, according to the spokesman.

Reduced bag shrinkage

In addition to providing capsular stability, capsular tension devices may inhibit the postop capsular bag shrinkage that takes place immediately after surgery and ends within 3 to 6 months.

According to a presentation by Sabine Kurz, MD, researchers found a small but significant difference in the amount of capsular bag shrinkage in patients implanted with both a hydrophobic IOL and CTR vs. IOL alone. Capsular measuring rings were implanted in all patients.

“Patients with the CTR had less shrinkage,” Dr. Kurz said.

In a study of 39 eyes, researchers found that patients implanted with the CTR had a median bag shrinkage of 10.4 mm to 10.25 mm, while patients in the IOL group had a larger “remarkable” shrinkage of 10.4 mm to 9.75 mm, Dr. Kurz said. This difference was statistically significant.

“We can conclude that the capsular tension ring inhibited capsular bag shrinkage in the study group,” she said.

However, she added, this conclusion can only be drawn upon the specific devices used.

“Further examinations would have to be performed to evaluate the influence of all tension rings and various IOLs on capsular bag shrinkage,” she said.

Reduced PCO

Capsular ring insertion A step-by-step guide for cataract surgery. Create scleral flaps Create a small capsulorrhexis away from the subluxated region. Perform gentle viscodissection Place sutures through the eyelet of CTR fixation hook Enlarge capsulorrhexis Hem the hook upward, over anterior capsule edge Place surgical needle between iris and anterior capsule, across the sclera, from the inside out Check bag centration with CTR in place Perform phacoemulsification, aspirate lens gently Insert a foldable IOL Recheck centration Create permanent suture knot; seal with scleral flap Source: Prieto I. Difficulties and complications of capsular tension rings with fixation eyelets. Presented at the Annual Meeting of the American Society of Cataract and Refractive Surgeons; April 14, 2003; San Francisco.

Another attribute of CTRs may be the reduction of posterior capsular opacification (PCO).

According to Frederic Hehn, MD, who has analyzed more that 400 eyes implanted with CTRs, the devices inhibit PCO, decrease capsular folds and improve IOL centration.

However, in his study, he found more specific CTR preventive factors for PCO. These factors are qualities of the CTRs that stabilize the capsular bag.

For one, PCO is prevented by the mechanical compression produced by the CTR on the capsular bag. Epithelial cell migration is blocked because there is limited space for the cells to migrate. The CTR causes a decrease of retro-optic space, he said.

These conclusions were reached from studies Dr. Hehn conducted comparing the rate of PCO in patients with IOLs and CTRs to the rate in those without CTRs. Dr. Hehn used various IOL types and materials, including hydrophilic acrylics and silicone, to determine the rate of epithelial cell migration.

Two years after implantation, 10% of patients without CTRs and 3% of patients with CTRs presented with PCO. For hydrophilic acrylic lenses, 20% of patients without CTRs experienced PCO, while only 5% of patients with the device did. In silicone lenses, 18% of patients without CTRs had PCO, as opposed to 4% of patients with CTRs.

“The most important factor in our patients with CTRs is that there were no capsulotomies in the first year,” Dr. Hehn said.

In fact, 17% of patients without CTR needed capsulotomies, while only 5% of patients with CTRs needed capsulotomy.

Insertion methods evolving

As CTRs continue to evolve, insertion methods for the devices are also evolving.

“Insertion is a problem with any method where you have a steep angle with the capsular equator that is undesirable, especially if there is a vault,” said Jaime Zacharias, MD. “We are looking to provide a CTR and insertion method that avoids pinpoint contact and sliding of the capsular bag equator.”

To achieve these goals, Dr. Zacharias and colleagues designed a new CTR specifically for easy, safe insertion.

“We modified an endocapsular tension ring with additional eyelets,” he said at ASCRS.

Dr. Zacharias said this modified ring can be used with conventional methods of insertion. However, he has designed three new methods of insertion to use with the eyelet ring.

The first, called the triserter method, avoids tension during insertion by using one hook and a separate active hook to bend the ring before insertion.

“This ring is bent and inserted through a small capsulorrhexis without creating tension in the bag,” Dr. Zacharias said.

The second method uses a suture as a tension cord to bend the ring.

“In this technique, we bend the ring inward and reduce its overall diameter. Then we reel the ring into the capsular bag and then release the cord,” he said. The ring expands once inside the bag.

The third method Dr. Zacharias and colleagues developed enlists the help of an inserter.

“An inserter has been designed to create tension throughout insertion, so that the CTR is delivered with a calculated amount of inward bending before its release into the capsular bag,” he explained. With these methods, he said, safer ring insertion is possible.

Miyake-Apple video showing atraumatic implantation of CTS. Note minimal displacement of the capsular bag and zonular stress during implantation. (All photos courtesy of Ike K. Ahmed, MD, FRCSC.)

For Your Information:

• Ike K. Ahmed, MD, FRCSC, can be reached at Credit Valley EyeCare, 3200 Erin Mills Parkway, Unit 1, Mississauga, Ontario L5L 1W8; Canada; (905) 820-6789; fax: (905) 820-0111; e-mail: ike.ahmed@utoronto.ca. Dr. Ahmed has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Michael D. Olson, OD, PhD, can be reached at Jules Stein Eye Institute, 100 Stein Plaza UCLA, Los Angeles CA 90095; (310) 206-1634; e-mail: olson@jsei.ucla.edu. Dr. Olson has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Sabine Kurz, MD, can be reached at the University Eye Clinic of Maintz, Langenbeckstr. 1, D-55131 Mainz, Germany; (49) 61-31-17-72-86; fax: (49) 61-31-17-66-20; e-mail: Kurz@augen.klinik.uni-mainz.de. Dr. Kurz has no direct financial interest in the products mentioned in this article, nor is she a paid consultant for any companies mentioned.
• Frederic Hehn, MD, can be reached at the Centre D’Affaires les Nations, Vandoeuvre, France; e-mail: hehnf@aol.com. Dr. Hehn has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Jaime Zacharias, MD, can be reached at the Fundacion Oftalmologica, Los Andes, Las Hualtatas 5951 Vitacura, Santiago, Chile; (56) 23-76-46-25; fax: (56) 23-71-89-34; e-mail: jzacha@entelchile.net. Dr. Zacharias has a direct financial interest in the modified CTR mentioned in this article. He is not a paid consultant for any companies mentioned.

• Ophtec USA, makers of StabilEyes capsular tension ring, can be reached at 6421 Congress Ave., Suite 112, Boca Raton, FL 33487; (561) 989-8767; fax: (561) 989-9744; e-mail: ophtecusa@aol.com; Web site: www.ophtec.com.
• Morcher GmbH can be reached at Kapuzinerweg 12, 70374 Stuttgart, Germany; (49) 711-95320-0; fax: (49) 711-95320-80; e-mail: info@morcher.com.