AUG 29, 2011
This article published in the July issue of the Archives of Ophthalmology reports the results of a study demonstrating the long-term effectiveness of a square-edged, closed endocapsular equator ring (E-ring) at preventing posterior capsular opacification (PCO) after cataract extraction. The authors found that none of the 51 eyes in this study required Nd:YAG laser posterior capsulotomy throughout seven years of follow-up compared with 23 of 51 control eyes (45 percent).
This article shows that the E-ring is a significant advance in our quest for permanent visual restoration after cataract surgery. There have been many ways of mitigating this problem, notably meticulous cortex removal, capsulorhexis edge placement on the lens optic and square-edged lens designs. However, when we do all we can today, the PCO rate is still accepted as 10 to 20 percent in older patients and far higher in younger patients. While much research has been done on the eradication of lens epithelial cells, no safe and effective way has ever been found.
A case study published in the Archives of Ophthalmology in April 2007 by the same researchers reported on the E-ring's efficacy in one patient followed for 2 ½ years after surgery, and evidence of its efficacy was published as far back as September 2001 in the Journal of Cataract & Refractive Surgery. It's a shame that patients in the United States aren't likely to benefit from the E-ring for years to come, since it has not yet been approved by the FDA.
The first 14 patients treated in the current study received an E-ring and IOL in one eye and an IOL in the fellow eye as a control. The remaining 23 patients (37 eyes) received an E-ring and IOL in one or both eyes, while 37 age-matched control eyes were implanted only with IOLs. After severe iritis developed in one eye, likely due to slight endocapsular ring rotation, the authors stopped using 9.0-mm rings and began using 9.5-mm rings instead.
In the initial group of 14 patients, the PCO value two years postoperatively in the central area of eyes with an E-ring was significantly lower than in controls (4.4 vs. 11.4, respectively; P = 0.005). The posterior capsule in eyes with an E-ring remained transparent without touching the IOL optic. The mean final visual acuity in eyes with an E-ring was 1.1 (range, 0.3 to 1.2). With the exception of the one eye with severe iritis, visual acuity was stable from one week until two years postoperatively.