Posterior capsule opacification and YAG capsulotomy

EODYMIUM:YTTRIUM-ALUMINUM-GARNET (ND: YAG) laser posterior capsulotomy is one of the most frequently performed ophthalmic procedures and as a consequence one of the largest expenditures to the national health care system (second only to cataract surgery itself). In 2002 approximately 650,000 YAG capsulotomies were performed on Medicare patients alone. Given the Medicare allowable fee of approximately 240 dollars per case, the expenditure for Medicare patients alone is 156 million dollars annually. Taken in combination with the fact that Nd:YAG posterior capsulotomy is occasionally associated with some morbidity, 1 Nd:YAG capsulotomy must be considered a major public health concern. Eradication of posterior capsule opacification (PCO) thus becomes an important goal of modern ophthalmology. Is this achievable and if so how? Smith and associates 2 present in this issue a study that attempts to determine which factor, intraocular lens (IOL) material, lens edge design, or amount of anterior capsule overlap on the IOL is most important in preventing PCO, studying both silicone and acrylic lenses. While their data indicate that overlap of the anterior capsule is the most important factor of those studied in preventing PCO, I believe that a number of factors, both surgery-related and IOL-related, act in a synergistic way which, when applied in combination, cause the greatest reduction in PCO. Apple and associates, 3 have previously reported on 5416 pseudophakic human eyes obtained postmortem. From information collected in this study and a review of the literature, they concluded that by applying six factors regarding surgical technique and IOL choice the incidence of PCO and hence the incidence of Nd:YAG laser posterior capsulotomy can be prevented or at least delayed. Of these six factors, three are considered to be “surgeryrelated” factors and three “IOL-related” factors. Surgery-related factors include: (1) Meticulous cortical cleanup, perhaps enhanced by cortical cleaving hydrodissection. 4 This minimizes the number of retained lens epithelial cells and cortex within the capsular bag and avoids the formation of a Sommering’s ring that may proliferate centrally to cause visually significant PCO. (2) “In-the-bag” IOL fixation. In-the-bag fixation of the IOL functions to enhance the IOL optic barrier effect which has been described by Peng and associates. 5 By placing the optic in contact with the posterior capsule (especially peripherally) proliferation of any remaining lens epithelial cells from the equatorial lens capsule is “blocked” by the barrier created at the contact point between the IOL and the posterior capsule. This theory was utilized in the design of some IOLs in the early 1980s. Examples included: IOLs that possessed peripheral barrier ridges like the Hoffer ridge, IOLs that utilized a meniscus designed optic, and IOLs that used posteriorly angulated haptics that positioned the IOL further back into the capsule so contact of the IOL with the posterior capsule was enhanced. (3) Creation of a continuous curvilinear capsulorhexis diameter slightly smaller than that of the IOL optic. This placement of the capsulorhexis edge over the optic helps provide for a tight fit of the capsule around the optic creating a “shrink wrap” effect that sequesters the IOL within the capsular bag and compartmentalizes the IOL (both the haptics and optic) from the vitreous cavity