|
Sean
Henahan
in San Francisco, US SYSTEMATIC capsular tension ring implantation appears to be an effective strategy for reducing posterior chamber opacification (PCO) following cataract surgery, suggests new longer-term study data presented at the annual meeting of the American Society of Cataract and Refractive Surgery. French specialist Frederic Hehn MD conducted a prospective study in which 373 patients received capsular tension ring implants. Patients all underwent phaco and lens removal while under local anaesthesia. A group of 86 cataract patients who had not received capsular tension rings served as controls. Patients who had received the capsular tension rings had significantly less PCO at three, six and 12 months and also at the two year mark. These results held up regardless of the type of IOL implanted - silicone, hydrophilic or hydrophobic acrylic. An analysis comparing treatment with and without capsular tension rings revealed some interesting findings for the different IOL types. At the two-year follow-up, 3% of patients who had received the hydrophobic acrylic Alcon Acrysof IOL required YAG capsulotomy, compared with 10% of those who received the same IOL but no ring - a statistically significant difference. Similarly, the YAG rate for those who received the hydrophilic acrylic Stabibag IOL and a capsular tension ring was 6%, compared with 20% for those who did not receive a ring. YAG rates were 4% for those who received the silicone Si55 or Clariflex AMO lenses with capsular ring, compared with 18% for those not receiving a ring. Dr Hehn noted that no patients who had received capsular tension rings required YAG treatment during the first year of follow-up. This probably decreased the risk for subsequent retinal detachment. Better centration was another apparent benefit of the capsular tension ring approach. This was observed in all types of IOLs used, particularly multifocal lenses. Poor centration has been a general problem with that type of lens in the past. The capsular tension ring may also be useful in the paediatric cataract setting, where PCO is rife. Dr Hehn described one case of a six-year-old cataract patient who remained free of PCO and did not require vitrectomy after 18 months of follow-up. The capsular tension ring was first used in complicated surgical cases. A recent study by Italian researchers (EJO 13:2;2003) provided long-term follow-up on some particularly challenging cases. Domenico D’Eliseo MD and colleagues at the Lugo Hospital in Ravenna, Italy utilised capsular tension rings during surgery in 118 eyes with cataract and severe zonular weakness. Eighty of the eyes received a 12.3/10mm Morcher capsular tension ring implant before undergoing phaco. The remaining 38 eyes did not receive a ring but were treated identically in every other respect. All patients received 5.0mm PMMA single piece IOLs (Corneal CM50M). One year follow-up data was available for 65 eyes of 62 patients with the capsular tension ring and for 36 eyes of 35 patients who did not receive the implant. The one-year examination included Snellen acuity testing, slit-lamp biomicroscopy, photography and evaluation with the three-mirror Goldmann lens. Some 4.6% of those in the capsular ring group developed grade 4 to 5 opacities requiring YAG treatment, compared with 11% if those in the non-CTR group. Moreover, 7.7% of those in the ring group showed moderate to severe PCO, compared with 36% in the non-implant group. These differences were statistically significant. The researchers note that many factors can contribute to the development of PCO. For example, it is generally recognised that the quality and thoroughness of hydrodissection and cortical clean-up can reduce the risk for PCO. However, in patients with zonular dehiscence, hydrodissection and careful clean-up can be dangerous. In such cases the capsular tension ring maintains the capsular contour and stretches the posterior capsule. Previous research by Rupert Menapace and others suggests that capsular tension rings prevent PCO through more than one mechanism. First, the rings cause posterior capsule stretching which reduces the IOL capsule distance. They also are believed to inhibit migration of lens epithelial cells with a discontinuous bending effect along the optic edge. The rings also serve to keep the anterior capsule leaf away from anterior optic surface and the posterior capsule. European surgeons can choose from an ever-growing array of capsular tension rings and inserters from different manufacturers including Morcher and Ophtec. Speaking at the ASCRS conference, Chilean surgeon Jaime Zacharias MD described a new variation in capsular tension ring design that may simplify their insertion. Dr Zacharias noted that standard capsular rings now in use typically include small rings or loops at either end of the device to aid in insertion. However, rings of this design can be difficult to manipulate and carry a risk of capsular tearing. He designed a new capsular tension ring that has more eyelets distributed along the circumference of the ring, which he says could improve both the insertion and safety of the device. The series of eyelets on the prototype allow the surgeon to better compress the ring while reducing the chances for damaging the capsule. Using a video, Dr Zacharias demonstrated different ways the device could be inserted safely. He has also developed a prototype inserter that appears to simplify the procedure considerably. Frederic Hehn MD |
