Age-related macular degeneration (AMD) is one of the leading causes of blindness in older people, with the "wet" form of the disease being responsible for about 90 percent of all cases of AMD-related severe vision loss. There may be new hope, however, in the form of an experimental eye implant.

In wet AMD, abnormal blood vessels growing beneath the retina cause its center section (the macula) to lift up and pull away from its base, leading to a loss of central vision. Introduced 12 years ago, a drug known as ranibizumab has been shown to slow that process, preventing blindness in over 90 percent of test subjects in clinical trials.

Unfortunately, though, people who are taking the drug must visit an ophthalmologist once every six to eight weeks, in order to receive injections directly into the eye. Given that many elderly patients either forget about these appointments or are unable to get to them, some of the injections are delayed or missed. As a result, the real-world effectiveness of ranibizumab actually sits at around 50 percent.

With that in mind, San Francisco-based biotech company Genentech developed the Port Delivery System. It centers around a device that is slightly longer than a grain of rice, which is permanently implanted into the eye – there, it slowly releases medication from its integrated drug reservoir. That reservoir can be refilled at a clinic via a circular port on the end of the device, which appears as a small dot on the surface of the eye, hidden beneath the eyelid.

In order to assess the effectiveness of the Port Delivery System at delivering a customized formulation of ranibizumab, a multi-center randomized trial recently took place, involving 220 patients who had received the implant. It was found that the device treated wet AMD just as effectively as the traditional injections, but patients could go for a median period of 15 months before requiring a refill.

Although there were some side effects to the initial implantation surgery, the system was found to be safe overall. It could be available for general use within about three years.

"Fewer injections and office visits is exciting," says study leader Dr. Carl D. Regillo, from Philadelphia's Wills Eye Hospital. "But more importantly, we think it will translate into better visual outcomes because in the real world, patients get less treatment than they need … If you're a week or two late for a visit from time to time, you may have a decline in vision, and you can't always recover from that."

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