A NEW APPROACH TO POSTERIOR CAPSULE OPACIFICATION AFTER CATARACT SURGERY

This month’s issue of EuroTimes is devoted to refractive lens surgery and features a number of thought-provoking and interesting articles on the subject. Our Cover Story is a particularly timely look at the issue of posterior capsule opacification (PCO) after cataract surgery, a complication which has diminished in recent years principally thanks to advances in IOL technology and improved surgical technique.

Looking at the progress made in reducing the incidence of PCO, the major advance has clearly been the knowledge that we should ensure that our intraocular lenses (IOLs) use a 360-degree sharp square-edge optic to act as a barrier to migrating lens epithelial cells. A review of the scientific literature clearly underscores the relationship between the introduction of square-edge IOLs and the corresponding decrease of PCO in our day-to-day clinical practices. Furthermore, we have just completed a review of our Dutch cataract guidelines, and what emerges very clearly is the square-edge design as being the single-most important deterrent to PCO formation irrespective of the lens material.

However, we need to be cautious in asserting the imminent demise of PCO. My own belief, based on clinical observation, is that PCO may well be occurring at a later stage in the postoperative period than we were used to with earlier IOL designs. While there has undeniably been a marked reduction in PCO in recent years, careful study of the Kaplan-Meier survival curves shows that the risk of late-onset PCO cannot be discounted.

The problem, of course, is that many surgeons nowadays do not follow-up their patients that rigorously, so the only information that we have is usually from short-term clinical trials with a maximum of six months or one year follow-up. If we apply the principles of evidence-based medicine, there is a clear lack of longer-term peer-reviewed studies, particularly of more recent IOL designs, that clearly demonstrate the PCO and YAG capsulotomy rates three or four years after surgery. We need the hard data to make informed decisions about lens choice and the risk of PCO formation for our patients.

In my experience, however, if PCO does not occur at the three-year postoperative mark and there is a clear capsular bag behind the lens, then that patient is very unlikely to be troubled by this particular complication.

With all the emphasis on lens designs, we also need to remember the role of the surgeon in reducing the incidence of PCO. We know now that the single most important factor in this respect is cortical clean-up. The surgeon has to take care to remove as much cortex as possible and carefully clean the equator of the lens to reduce the risk of PCO.

We have also had to rethink some of our old orthodoxies concerning PCO. For instance, it was once widely believed that meticulous cleaning of the anterior capsule was beneficial in decreasing fibrosis and reducing PCO, but it turns out that this is not the case. On the contrary, we discovered that polishing of the anterior capsule is not needed and is counter-productive, because we need the cells of the anterior capsule to generate the shrink-wrap effect with the IOL that has helped to lower the PCO rate.

So I think this example behoves us to be cautious in transferring early science in vitro into clinical relevance with respect to the open capsule designs that are currently being proposed. The technology and concept certainly looks promising, but we need to design some solid clinical trials to learn more about their safety and viability. If the concept proves to be worthwhile, we should probably first start by using a monofocal lens, with a kind of haptic fixation that would create a kind of open bag, to see whether this is beneficial. I think we can certainly look forward to some exciting innovations in the future and hopefully reduce the incidence of PCO even more.