Regional EuroTimes
Date Posted 15/09/2009
Fibrosis, PCO could interfere with long-term function of ‘special’ IOLs
A high proportion of presbyopia-correcting lenses are likely to lose their function over time, predicted David Apple MD, US. Based on his studies of IOLs explanted at autopsy, he believes that opacifications are very common even among lenses that demonstrate very low PCO rates in three-year studies, and that even a small amount of epithelial cell growth, fibrosis or calcification may irreparably damage the delicate optics and mechanisms of modern presbyopia-correcting lenses.
“We predict that an unsatisfactory number of these lenses will not provide the safety and efficacy we expect over the long term, 10 years or more,” Dr Apple said.
Laser capsulotomy is not a solution because lasering these lenses also is likely to render them non-functional, Dr Apple noted. “Until recently, surgeons didn’t care about PCO, you just did a yag and no problem. But now PCO can obviate the function of these various refractive lenses. You need a clear media and a non-stiff lenses to get the movement and so forth that you need from these lenses,” Dr Apple said.
Dr Apple’s study of cadaver eyes shows that even among hydrophobic lenses with very low three-year PCO rates, up to 50 per cent will develop PCO over the patient’s lifetime. Similar long-term events such as calcification, glistenings and epithelial ingrowth between piggyback lenses are also very common, and can cause lens failure, he said.
Emmanuel Rosen MD, UK, questioned the conclusion, noting that such problems are rarely reported. “There are very few case studies presented at this and other conferences.”
Dr Apple responded that “special” lenses are much more sensitive than monofocal IOLs, which magnifies the problem. Even if 80 per cent of the lens is clear, it is enough to destroy its function.
Dr Apple criticised the FDA standard of one- to three-year studies as inadequate for evaluating modern lenses. His studies show a sharp and continuous increase in opacifications past three years. He recommends longer-term studies to better understand how IOLs fare over time.
“The FDA mantra is one to three years. We consider this way too short. Once these lenses are approved for one to three years, they are just out there and no one knows what happens to them. We are putting them in younger and younger patients and I think it is going to be a problem in the future. PCO and fibrosis has reached a new level of interest. It is not just a matter of yagging the patient and going home,” Dr Apple said.
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