Capsular Tension Rings

Cataract surgery in an eye with absent or weak zonules presents unique challenges for the anterior segment surgeon. With the introduction of the capsular tension ring (CTR), and its several modified versions, the ability to perform safe cataract extraction with the implantation of a stable and well-centered intraocular lens (IOL) within the capsular bag has increased substantially. In order to use CTRs safely and effectively, the modern cataract surgeon must have a thorough understanding of their design, indications, methods of insertion, and limitations. Although there were descriptions of endocapsular ring devices made in the 1980s (initially intended to decrease capsular fibrosis), it was not until 1991 that the idea of the use of an endocapsular device solely for the purpose of maintaining a circular bag was published. In 1993, Leger and Witschel introduced the first iteration of the modern open-ringed polymethylmethacrylate (PMMA) CTR and demonstrated its placement in a human eye during cataract surgery. Multiple studies and variations have followed, but the simple design and concept behind this revolutionary device has remained. Description of the Device The CTR is a PMMA open-ring device with blunttipped eyelets at either end (Figure 14-1). The CTR is designed to be implanted into the capsular bag and left permanently in place. CTRs work by imparting a centrifugal force to the equator of the capsular bag. This force is equalized throughout the entire zonular-capsular apparatus, thereby transmitting the tension from intact and normal zonules to those areas of zonule laxity or absence. By increasing overall bag stability, the risk of intraoperative complication is reduced. In addition, the tension imparted to the entire bag with a CTR decreases postoperative capsular contraction (phimosis) and posterior capsular opacification and improves IOL centration. CTRs appear to have no effect on the refractive results from cataract surgery. Whether or not a CTR will decrease the rate of late IOL/bag subluxation is still being evaluated and debated. In order to be most effective, the CTR should be larger in diameter than the capsular bag diameter and an appropriately sized ring should have its ends overlap slightly. Ultrasound biomicroscopy has shown that a correctly placed CTR lies between the IOL haptic and the ciliary body with no iris touch, and that its position is stable, safe, and consistent. Capsular Tension Rings