October 2015

 

RETINA

 

Device focus

Newer diagnostics for AMD


by Michelle Dalton EyeWorld Contributing Writer

 
 

We need to directly communicate with the cataract surgeon about the visual potential to help them decide if moving forward with cataract surgery will be beneficial. J. Michael Jumper, MD

 
optical coherence tomography

Above, patient being examined with optical coherence tomography (OCT); below, fluorescein angiogram to help determine disease state

fluorescein angiogram Source: Bayer Germany Retina Image Collection, produced by Karl Brasse, MD

What anterior segment surgeons need to know about diagnosing AMD

In the years since the antivascular endothelial growth factor drugs were introduced, treating age-related macular degeneration (AMD) has become less about delaying disease progression and more about reversing the damage already done. Part of that strategy includes being able to diagnose the disease earlier and earlier. A genetics task force is planning a report this fall to address the potential benefit of genetic testing and/or vitamin use in the realm of retinal disorders, but details were not available at press time.

Diagnostic tools

Optical coherence tomography (OCT) is typically used to confirm treatment efficacy. Whether or not OCT-angiography, one of the newer tools, is clinically useful is still being debated. On the one hand, OCT-A does not show leakage, which is what matters, said Steve Charles, MD, Charles Retina Institute, Germantown, Tenn., who added spectral domain OCT is the optimal way to determine who needs an injection and who does not. But its quite exciting to be able to find choroidal neovascularization (CNV) using OCT-A, where that information is already captured in many of the machines that we have, said J. Michael Jumper, MD, West Coast Retina, San Francisco. OCT-A is mostly software changes that could, hopefully, allow us to be able to see CNV without having to do a fluorescein angiogram. While he agrees there are some limitations to the technology, itll put angiography in the hands of more people, he said. Whether the technology will allow clinicians to readily identify choroidal neovascularization better than current technology remains to be seen.

Dr. Charles firmly believes OCT-A is not a game changer. The technology will continue to be academically interesting, and may be a research tool, but it has a tremendous problem with motion artifacts that will prevent it from becoming a highly valuable clinical tool.

Dr. Jumper said diagnostic tools such as the AMD home monitoring devices seem to have real value. The ForeseeHome AMD Monitoring Program (Notal Vision, Chantilly, Va.) monitors progression of AMD and appears to be more sensitive in detecting early changes. Its the first commercially available home monitoring device.

Its possible these devices can help improve outcomes in people with AMD by detecting choroidal neovascularization earlier, Dr. Jumper said. The test results are transmitted to a central monitoring system that will alert physicians to immediate, significant visual field changes in their patients, so that patients can be recalled for timely follow-up and necessary treatment may be initiated.

Encapsulated cell technology

Dr. Charles said the real research being done at the molecular level and with molecular targeting is what the next phase is all about. Encapsulated Cell Therapy (ECT, Neurotech, Cumberland, R.I.) is a first-in-class, versatile drug delivery platform in development for the treatment of a broad array of ocular disorders. ECT is a genetically engineered ocular implant that enables continuous production of therapeutic proteins to the eye for more than 2 years. Additionally, the therapy is reversible by simply removing the implant, the company said.

The potential is great, Dr. Charles said, especially for rural patients who cannot afford monthly visits to a retina clinic or who have physical limitations where getting to a retina clinic is difficult. ECT has a track record in retinitis pigmentosa, Dr. Jumper said, and may have a role in AMD. Simply put, ECT uses living cells encapsulated within semipermeable polymer membranes and supportive matrices. The technology allows a therapeutic agent to be engineered into the cells; by encapsulating the cells the technology prevents immune system rejection while still allowing the therapeutic product to disseminate to their target sites.

Unlike gene therapy, this technology is reversible, which makes it more attractive, Dr. Charles said.

Drug reservoirs

Numerous retinal disorders mandate monthly monitoring and/or treatment, and refillable drug delivery devices may one day be the thing thats going to help decrease the retreatment rate, Dr. Jumper said. But the technology would bring with it as many questions as it addresses, namely cost, implantation techniques, and patient selection, among others.

There is the potential for extrusion with these types of devices, Dr. Charles cautioned. Theres a high likelihood of extrusion of these large implants in the subconjunctival space, especially because of the need to utilize needles to replenish the reservoir periodically. He equates the technology to glaucoma valve implantsand that vitreoretinal specialists often treat patients with blebitis or endophthalmitis resulting from a breakdown of the bleb and its subsequent infection.

Some of the more promising devices are on the cusp of starting larger phase trials that will address some of the questions/concerns, but for now, its very difficult to know what will come out on top and whether or not its any better than what were doing now, Dr. Jumper said.

AMD and cataract surgery

Knowing the visual potential for an eye with both AMD and cataract is crucial in managing patient expectations, Dr. Jumper said. We need to directly communicate with the cataract surgeon about the visual potential to help them decide if moving forward with cataract surgery will be beneficial, he said. Cataract surgery itself has no impact on AMD progression, and anti-VEGF therapy can and should be continued on schedule while proceeding with cataract surgery, Dr. Charles said. Further, if the patient has dry AMD, theyre not likely to convert to wet because of the cataract surgery, Dr. Jumper said. Dr. Charles recommends patients receive an anti-VEGF injection a few days before phaco, but Dr. Jumper is more comfortable with a few weeks between the two procedures to eliminate questions about postop/post-injection inflammation or infection.

Well-constructed wounds do not need to be sewn closed, and because injections place very little external pressure inward on the eye, wound complications as a result of an intravitreal injection are uncommon.

Editors note: Dr. Charles has financial interests with Alcon (Fort Worth, Texas). Dr. Jumper has financial interests with Allergan (Dublin, Ireland), Genentech (South San Francisco), Ophthotech (New York), and Regeneron (Tarrytown, N.Y.).

Contact information

Charles: scharles@att.net
Jumper: jmichaeljumper@gmail.com

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