Dry AMD:  A new target for treatment

 The “wet” form of age-related macular degeneration remains the leading cause of blindness in developed countries throughout the world.  The dry form is usually of less concern to most practitioners.  We now realize, however, that some forms of dry AMD do lead to blindness and that by identifying “high risk” dry AMD patients, we may be able to prevent or reduce the risk of “wet” macular degeneration.  Here we review the current and developing treatments for patients with dry AMD.

Forms of dry AMD

Dry AMD presents in two main forms – drusen and geographic atrophy.  Large drusen also called soft or confluent, are associated with a much higher risk of developing wet AMD and in most patients cause little or no significant vision loss.  Geographic atrophy, on the other hand, is often progressive and can lead to severe vision loss.  Studies are now differentiating the two forms and treatments are directed at one or the other.

 Nutrition

The Age-Relates Eye Disease Study II (AREDS II) is now underway and the scientific data supporting the AREDS II formulas have begun to alter present day recommendations. There is ample data to support the consumption of xanthophyllic carotenoids, Lutein (10 mg/d) and Zeaxanthin (2mg/d), which were not part of the AREDS I study.  There is also data to suggest that lower Zinc levels may be safer as well as effective and this is under study.  Finally, the benefits of DHA enriched omega 3 fatty acid formulations is supported by smaller studies and is under formal evaluation.  A ratio of EPA/DHA of 800/600 is used in AREDS II.

 Apoptosis

The geographic atrophy that can lead to complete central vision loss in dry AMD appears driven by programmed cell death or “apoptosis”.  Clinical trials are focusing on this and the Allergan sponsored study of the anti-glaucoma drug, brimonidine, shows promise.  An antidepressant that can block apoptosis is under evaluation by Alcon.

 Implants, transplants and transfection

Artificial retinas are under development by several agencies and show great promise.  Other retinal degenerations like retinitis pigmentosa are the primary target but dry AMD, where the outer retina is similarly destroyed but the inner retina is preserved, is a target disease as well.  Retinal transplantation has been performed extensively in animal models and preliminary results in humans show some promise.  Using stem cells from bone marrow injected beneath the retina appears to be a viable option and a potential source for future human studies.  Transfection of retinal cells by adenovirus vectors carrying drugs that attach macular degeneration as well as diabetic retinopathy is a promising route for drug delivery and studies in humans are already underway.

While wet AMD remains the focus for must practitioners, dry AMD is potentially more important since slowing or reversing this disease can not only prevent wet AMD but also prevent blindness from a  currently untreatable form of this condition – geographic atrophy.  New clinical studies are underway for these patients – let your patients know there are new options and hope.

Ron P. Gallemore, M.D, Ph.D.

Founder and Director

Retina Macula Institute and the

Retina Macula Research Center

South Bay 310-944-9393

Los Angeles 310-466-9393