By Nathan Welton
South Coast Beacon
It’s pretty easy to see through a clean window, or even one covered in a light mist, but a torrential downpour hopelessly blurs the world beyond the glass. A similar phenomenon happens to patients with age-related macular degeneration (ARMD), who suffer from an overgrowth of plaque on the inner parts of their eyes.
And while anyone with a squeegee can clean windows, the blind can’t do so to their retinas – which has led a team at UCSB’s Neuroscience Research Institute to explore ARMD plaque deposits.
What they’ve found, according to their recent publications and lectures, is that these plaques — called drusen — may be caused by inflammations triggered by a protein called amyloid beta, the same protein that causes inflammation and, subsequently, plaque deposition in the brains of Alzheimer’s patients. In both cases, the plaques crowd out functional nerve cells and cause visual or mental degradation.
Linc Johnson, a scientist at the Center for the Study of Macular Degeneration at UCSB, explained that this similarity may spawn a future of cooperative study between the two fields, so that Alzheimer’s researchers could take advantage of discoveries in the ARMD arena, and vice versa, in order to expedite the development of treatments and preventions.
“Our research closely ties the disease process in Alzheimer’s to that in macular degeneration,” he said. “It happens in different organs, but it’s very similar.”
Macular degeneration occurs in over 30 percent of adults over the age of 75, causing blurry vision that can lead to functional blindness. Some fear the disease could hit epidemic proportions by the time aging baby boomers begin retiring
“There is a reason why macular degeneration is the leading cause of blindness in people over the age of 65: there is no good way to treat it,” said Marc Lowe, a Santa Barbara retina specialist. “We can slow it down with laser treatment, but we can’t stop it in its tracks.”
The eye’s lens and cornea bend incoming light and focus it onto the retina, in the back of the eyeball. The retina contains cells called photoreceptors that turn light into nerve impulses that travel to the brain. The macula, which is affected by ARMD, is a small region of the retina responsible for fine, centralized vision.
Like all cells, photoreceptors continually die; when this happens, the body mounts an immune response to clean up the mess and heal the damage. An intrinsic part of the response is local inflammation, which leaves behind byproducts that over time appear to cause drusen, the ARMD-specific plaque.
“Drusen are actually quite common in elderly people,” said Johnson. “But it’s when drusen form in high numbers, or large areas are covered drusen that have merged, that vision becomes threatened.” He explained that even small numbers of drusen can cause minute areas of vision loss, but the eye can compensate for this because it is wired for redundancy.
A few years ago, scientists discovered that anti-inflammatories like ibuprofen, when taken for long periods of time, could cause a 50 to 80 percent decrease in the incidence of Alzheimer’s progression, and “one of the things that would be obvious to try is to see if that would have the same effect on ARMD,” said Johnson.
The connection made at the Center for the Study of Macular Degeneration may open huge troves of information for ophthalmologists, who could apply future discoveries in Alzheimer’s research, like the development of vaccines or genetic treatments, to the field of age-related blindness.
But the relatively new discovery causes some doctors to pause. Robert Avery, local ophthalmologist, said the ARMD and Alzheimer’s are clinically very different, noting that a link between the two is possible but that more work would need to be done.
Lowe, too, said he would need more definitive proof before believing the two diseases are related.
“I have hundreds, maybe thousand, of patients that have macular degeneration in my practice, and I’m trying to think offhand of how many have coexisting Alzheimer’s,” he said. “I would say that almost none of them do. There’s no reason for me to think there’s a direct link between the two.”