SUNDAY, Sept. 27, 2009 (HealthDay News) -- Already a leading cause of vision loss among people older than 60, age-related macular degeneration is expected to skyrocket in numbers over the coming decades as the U.S. population grows older.
However, a series of new treatments now under study or in development should mean that eye specialists will be well-prepared to treat the coming surge of macular degeneration cases.
These include refinements of treatments that have proven effective against some forms of the disease as well as new therapies targeting forms of macular degeneration that have so far proven impossible to treat.
Age-related macular degeneration involves the breakdown of the macula, which is located in the retina and helps provide clear central vision. As the macula deteriorates, people see a blurred spot in the center of their vision that grows over time.
Macular degeneration comes in two forms, wet and dry. Current treatments for the wet form of the disease -- in which abnormal new blood vessels in the eye cause leakage and bleeding -- have proven quite successful. The wet form is more rare but can cause rapid vision loss if not caught early.
Researchers have discovered a combination therapy of vitamins and antioxidants that reduces the risk of progressive vision loss by more than 20 percent, said Dr. David W. Parke II, executive vice president and chief executive of the American Academy of Ophthalmology.
Other progress against the wet form of the disease has come through the use of drugs that target vascular endothelial growth factor, or VEGF, a substance in the body that promotes the growth of new blood vessels.
"We now have treatments where, when we catch people early in the course of the disease, the chance of vision loss is less than 10 percent over a two-year period," said George Williams, chairman of ophthalmology and director of the Eye Institute at William Beaumont Hospital in Royal Oak, Mich. Those treatments also provide a 20 to 30 percent chance of significant vision improvement over the same period.
No effective treatments have been found for the dry form of macular degeneration, which causes less catastrophic vision loss but accounts for 85 percent of all macular degeneration cases, according to the U.S. National Eye Institute. The dry form occurs when the light-sensitive cells in the macula begin to slowly break down.
New advances in the treatment of the wet form involve further research into vitamin combinations that can help slow the progress of macular degeneration, Parke said. An ongoing trial is looking into whether diet or supplements can better improve a person's chances of retaining clear vision late in life.
"Around the world, there are culturally different rates of progression," Parke said. "The question becomes, how much of this is dietary?"
Research also has focused on the two drugs currently used to target VEGF, with a head-to-head study now looking into which of the two is more effective. "It's a very important trial, and I think all involved are looking forward to seeing if these drugs have a lot of differences," Parke said.
Other anti-VEGF drugs are in the pipeline, Williams said, and studies are testing ways to combine anti-VEGF medications with radiation or laser therapy to produce better results.
Cutting-edge research also may have found another way to tackle the wet form of macular degeneration. In the June 14 issue of Nature, doctors reported that blocking the activity of a specific protein can reduce the same blood vessel growth that leads to the wet form.
"We now have the opportunity to develop drugs that target this protein that may be safer and more effective than our current treatments," Parke said.
As far as the dry form of macular degeneration, eye experts are exploring ways that drugs used to treat other nerve-damaging diseases such as Alzheimer's might be able to help save people's eyesight, Williams said.
"We're fairly optimistic that within three to five years we'll have a treatment for the dry form of macular degeneration," he said. "We know what happens is the nerve cells that sense the light are dying off. The thought here is if we attack the process that makes them die, we can save the vision."
The U.S. National Eye Institute has more on macular degeneration.