Capsular tension rings increase options for cataract surgery

San Diego-Now that capsular tension rings (CTRs) from both AMO/Ophtec and Morcher have been approved, surgeons need to know which eyes can best benefit and which eyes should not receive CTRs.

Kenneth J. Rosenthal, MD, FACS, of Rosenthal Eye and Facial Plastic Surgery, Great Neck, NY, participated in the U.S. clinical trials of both models of CTRs and offered suggestions on their successful use here at the annual meeting of the American Society of Cataract and Refractive Surgery.

"Intraoperatively, be alert to signs of an unstable anterior chamber, trampolining of the iris, and hypermobility of the lens and capsule during capsulorhexis, hydrodissection, or phacoemulsification," Dr. Rosenthal suggested. In these cases, Dr. Rosenthal also recommended using dye (either trypan blue or indocyanine green) to improve control during capsulorhexis.

Sizing CTRs There are not yet any definitive studies or even a clear consensus on how to choose the size of a CTR, Dr. Rosenthal said, but his experience has led him to adopt some basic principles.

"It is really a merger of two issues," he explained. "One is the white-to-white measurement of the eye. The other is the presence and degree of capsular laxity. There have been a number of studies that have shown white-to-white measurement closely correlates to capsular diameter. The size of the tension ring can then be chosen accordingly.

"If you have no laxity, you want to choose a smaller ring size that will fit inside the capsule and give added stability," Dr. Rosenthal said. "If there is some laxity, you might want a larger ring to create more tension."

When it is clear that a surgical case could benefit from a CTR and the appropriate-size ring has been chosen, the next decision is how and when to implant it.

"Insertion can be done successfully by a manual technique," Dr. Rosenthal said, "but the inserters available from AMO/Ophtec for their ring and Geuder [Heidelberg, Germany] for the Morcher ring are very useful and simplify the insertion process."

According to Dr. Rosenthal, the key to successful use of the CTR is to insert the ring as late as possible-but as early as necessary-during the procedure. This is to avoid a situation in which the ring could actually hamper the progress of surgery, he explained.

"You don't want to insert a ring too early because it could trap cortex," he said. "When I have to insert the ring before the nucleus and cortex are removed, I first remove the anterior and equatorial cortex, inject viscoelastic under the rim of the anterior capsule, to push the nucleus and residual cortex back behind the equator of the lens, and then slide the ring just under the anterior capsule. This helps prevent the entrapment of cortex."

Contraindications to use of a CTR are also becoming clear.