October 2008

 

CATARACT/ IOL

 

Capsular tension rings: optimal implantation time


by Michelle Dalton EyeWorld Contributing Editor

 

 

How to recognize situations that may benefit from CTR insertion

Subluxated crystalline lens of patients with Marfan’s syndrome represents a case for the capsular tension ring

Using an injector through a side-port incision to introduce the capsular tension ring into the eye under control of a hook Source: I. Howard Fine, M.D., Richard S. Hoffman, M.D., and Mark Packer, M.D.

A hook delivers the trailing end of the capsular tension ring intothe capsular bag Source: I. Howard Fine, M.D., Richard S. Hoffman, M.D., and Mark Packer, M.D.

Capsular tension rings, or CTRs, have been approved for use in the United States for several years now, and are designed to improve the outcome of phacoemulsification when the capsular bag stability is compromised. This kind of instability is most often found in cases of pseudoexfoliation, floppy capsule syndrome, Marfan’s syndrome (and other metabolic disorders), eyes that have undergone previous trauma (including vitrectomy), and high myopia. The CTR performs by essentially exerting a centripetal pressure equally balanced over the equatorial region of the bag. The benefits of implanting a CTR seem to be improving the IOL centration in eyes with zonular weakness, less IOL tilt, and less anterior and posterior opacity, leading surgeons say.

They are not without contraindications, including the presence of an unwanted opening in either the anterior or posterior capsule, or eyes with extremely compromised zonules (more than five clock hours). Yet there still remains a question about the ideal implantation time during surgery—right after the capsulorhexis or later, after the cortex has been removed. Factors that may play a role in the decision are lens density, size of the zonular dialysis, and the amount of clock hours of zonular dehiscence exist. EyeWorld asked several leading authorities for their pearls on the topic.

Not always recognized

Zonular weakness may not be readily recognized at the start of phacoemulsification, said Terry Kim, M.D., associate professor of ophthalmology, Duke University School of Medicine, Durham, N.C.

“Trauma or pseudoexfoliation cataract are cases where surgeons should definitely anticipate needing a CTR,” he said. Some surgical hints that the patient might require a CTR include a large clock hour of dehiscence, “where you’ll even see the edge of the capsular bag,” Dr. Kim said. Other subtleties to look for, he said, are when the capsular bag is very flaccid after cortex removal. Also, he said, as patients age, zonules naturally become weaker, “especially if they’ve undergone other surgeries,” Dr. Kim said. One method Dr. Kim uses to determine if a CTR might be needed is to have the patient look away and then fixate on him. “Some-times you’ll be able to see if the lens shakes,” he said. “Otherwise, you’re going to have to wait until you’re in the midst of surgery.”

Patients with very dense or brunescent lenses may also benefit from having CTRs.

“You may have a patient who’s a high myope and the vitreous support isn’t there,” Dr. Kim said. “Especially after a large lens removal, you might be left with a very flaccid capsule. But preoperatively, the initial scenario might not have a surgeon planning on CTR use.”

Defining zonular weakness

Both the number of clock hours and the severity of zonular instability are keys to categorizing the etiologies, said Iqbal (Ike) K. Ahmed, M.D., assistant professor, University of Toronto, Toronto, and clinical assistant professor, University of Utah, Salt Lake City. Overall, Dr. Kim said, surgeons can consider the zonular dehiscence mild if it’s one or two clock hours, moderate if it’s three or four, and significantly weakened if it’s more than five or six clock hours. There have been several articles in the literature that discuss some potential complications of CTR use. Among the intraoperative complications are tearing of the capsulorhexis, increasing the pre-existing zonular dehiscence that can result in vitreous prolapse, and further dislocation of the bag.

Postoperatively, surgeons may notice corneal edema, mild or persistent iritis, or broken sutures. Much less likely, but possible, are retinal detachments, best corrected visual acuity loss, and posterior capsule opacification.

Insertion pearls

Dr. Ahmed and colleagues found early insertion (i.e.: right after the capsulorhexis) can be traumatic and cause further stress when compared to late insertion (i.e.:after cortex removal).1 The later in the case a conventional CTR can be inserted, the better, advised the late Joel K. Shugar, M.D., M.S.E.E., in a phone interview with EyeWorld shortly before his death. In cases of serious phacodenesis, he recommended inserting the CTR immediately after hydrodissection. In cases of mild zonular weakness, however, he would wait until after the cortical removal is completed.

In most cases, Warren Hill, M.D., Mesa, Ariz., also places the CTR after removal of the lens nucleus and prior to finishing cortex removal.

“For those who are inexperienced, I recommend that for their first few implantations, they go very slowly during insertion and closely watch the capsular bag for signs that something may not be proceeding correctly,” said Dr. Hill.

“The trauma of insertion can be avoided with a few technique pearls,” Dr. Ahmed said. For instance, he said, if the decision is to implant the CTR early, a key pearl is to viscodissect 360 degrees right after the capsulorhexis.

“You’re not looking for a posterior wave, just to separate the cortex from the anterior chamber to the equator,” he said, and follow immediately with implantation and hydrodissection. “A primary benefit of placing the CTR early is to protect against vitreous herniation,” he said, “and to help avoid bag collapse during the end of phaco and during cortical removal.”

Dr. Kim also prefers late implantation, as cortex removal can be “extremely difficult” if the CTR is implanted too early.

“In mild dehiscence, you should put the CTR in and direct it toward the area of zonular dehiscence. At 3-4 clock hours, you should really orient it so the direction of the insertion is opposite the greatest zonular weakness,” Dr. Kim said. Samuel Masket, M.D., “summed it up beautifully in saying that his preference is to implant a CTR ‘as late as you can and as early as you must,’” Dr. Hill said. Injector use Although using an injector isn’t required, it’s usually recommended.“I always use an injector and love the control of being able to insert at the plane of the capsule, and move the injector backwards in counterclockwise manner to assist in CTR insertion,” Dr. Ahmed said. He prefers to inject clockwise, and tries to inject into the dialysis. “If necessary, I use a Kuglen hook to provide counter traction on the anterior capsule if the lens is mobile or torquing during insertion,” he said. “The key point is don’t let the lens torque too much or displace excessively otherwise this means you are putting too much stress on the zonules during implantation. I find the use of the Kuglen hook or Lester to be very helpful to hold the capsular bag 180 degrees away from CTR insertion site.”

Also, he said, try to ensure the capsulorhexis is at least 5.5 mm to ease CTR implantation and overall phaco and cortical removal if the CTR is inserted early on.

Dr. Kim echoed those suggestions, and recommended those unfamiliar with CTR insertion use an injector system. “Also, make sure the capsule is fully inflated,” he said. “I recommend loading the CTR, grabbing it with an angled forcep and loading it from the left side of the ring. The Sinskey hook should point toward the ground, and that should engage the CTR. Slowly release it and it will load onto the injector.”

He added an additional incision might have to be made, as the area of greatest zonular dehiscence may not be directly opposite the initial incision. Dr. Shugar’s recommendation noted injectors made the implantation easier, but that surgeons needed to be vigilant in ensuring the clock hours not serviced by the CTR are not weak zonules. Another reminder, Dr. Ahmed said, is not to let the anterior chamber shallow at any time during the case. “Use balanced salt solution injected through the sideport, or more OVD to ensure the anterior chamer doesn’t shallow,” he said. “If it does, you’re at a high risk of the vitreous coming around the dialysis.”

Other advantages CTRs in general not only provide support during surgery, but support the IOL long term, Dr. Kim said. “In trauma cases, the dehiscence is not progressive, but in pseudoexfoliation it may be, and that patient may end up with a decentered lens and bag,” he said. In the U.S., the Cionni modified CTR fixates the device, as it includes an extra loop to suture to the sclera to support the whole bag. The Ahmed CTR fixates the bag in one location. A newer design is available in Europe with “truncated edges so you can move around and strip the cortex away from it a bit easier,” Dr. Kim said. Surgeons will continue to find new indications for these rings, Dr. Kim believes. “As we all get more comfortable and more skilled at identifying potential complications, we’ll begin using capsular bag support systems more,” he said. “That doesn’t only include CTRs, but capsular tension segments, modified CTRs, and capsular retractors.”

The key for future use, he said, is to recognize the role each device plays and get the best outcomes with each device, Dr. Kim said.

Editor’s note: Drs. Kim and Hill do not have any financial interests related to their comments. Dr. Ahmed has financial interests with the Ahmed CTR.

Contact:

Ahmed: 905-820-3937, ike.ahmed@utoronto.ca

Hill: 480-981-6111, hill@doctor-hill.com

Kim: 919-681-3568, kim00006@mc.duke.edu

Reference:

1 Ahmed IIK, Cionni RJ, Kranemann C, Crandall AS. Optimal timing of capsular tension ring implantation: Miyake-Apple video analysis. J Cataract Refract Surg. 2005;31:1809-13.

Capsular tension rings: optimal implantation time Capsular tension rings: optimal implantation time
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