"We (surgeons) need to decide which IOL will obtain the best final outcome," said Dr. Nichamin, medical director, Laurel Eye Clinic, Brookville, PA. He outlined the strengths and weaknesses of the latest IOL technology during the meeting, sponsored by Johns Hopkins University School of Medicine, Baltimore, and Ophthalmology Times.
The crystalens (eyeonics), ReZoom IOL (AMO), and the AcrySof ReSTOR IOL (Alcon Laboratories) are the three lenses that all perform quite well, although there are subtle differences, he noted.
The crystalens accommodating IOL, a biconvex silicone plate lens with 4.5-mm optic, approved in November 2003, offers good distance vision, excellent intermediate vision, and minimal nighttime vision symptoms. With this lens, patients are able to achieve 1 to 1.5 D of pseudoaccommodation, which helps with intermediate vision, Dr. Nichamin said.
"This is where the crystalens really shines, basically, 100% across the board at 1 and 3 years," he said. "These lenses get better over time."
Intermediate vision is becoming extremely important with more people spending time on computers as well as using hand-held electronic devices. Today, among those 50 years and older, computer usage is strong. More than 40% of 79 million adults over 50 access the internet 11 to 30 hours per week, which translates into 2 to 4 hours per day. By 2015, the adult population of 50 and older will be 106 million.
Cell phone, personal computer (PC), and personal digital assistant (PDA) use has grown exponentially over the last 5 years. From 2000 to 2005, worldwide mobile phone shipments have grown from 413 million to 740 million. During that same period, portable PCs have taken off from 134 million shipments in 2000 to 182 million shipments in 2005, and PDA use has also increased from 11 million in 2000 to 39 million shipments last year, Dr. Nichamin said.
"The limitation of the crystalens is that it is a little weaker at near uncorrected vision," Dr. Nichamin said. "It is somewhat unpredictable. The FDA trials indicated 1 D of accommodation. I would say that one achieves about 1 to 1.5 D of accommodation compared with a monofocal lens. Basically, enhanced pseudoaccommodation is taking place."
Another potential drawback with this IOL is capsular contraction syndrome, also known as Z syndrome, which may occur because of the hinged haptics. In his experience of implanting several hundred crystalens IOLs, Dr. Nichamin said he has never had this problem. The key to avoiding the problem is good cortical cleanup. However, if it does occur, the surgeon can perform a YAG laser capsulotomy, he said.
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