New research from scientists at the University of Maryland School of Medicine (UM SOM) has found that tiny lumps of calcium phosphate may be an important triggering factor for age-related macular degeneration (AMD), a degenerative eye disease that can cause severe vision loss and blindness. This is the first time these mineral deposits have been implicated in the disease, which affects more than 10 million Americans. The article appeared in the latest issue of the Proceedings of the National Academy of Sciences.

Biochemist Richard Thompson, PhD, along with his colleague from University College, London, Imre Lengyel, PhD, and a multidisciplinary international team studied retinal samples from a group of elderly patients, some of whom had AMD. They found that the AMD samples contained tiny spherules of a mineralized calcium phosphate known as hydroxyapatite, or HAP. HAP is common in the body – it comprises the hard part of bones and teeth – but it had never been identified in that part of the eye before.

AMD develops slowly over decades, with the buildup of fatty protein deposits in the retina, which cause damage by blocking the flow of nutrients into the light-sensitive portion of the eye, and of waste products out. Scientists have known about these deposits for over a century, but their origins remained a mystery. Thompson and Lengyel discovered that the deposits appear to form around the tiny bits of HAP. Once these chunks appear, the fatty protein material coalesces around it; over years, these globules build up.

They discovered the possible role of HAP by examining tissue samples from patients using X-ray diffraction and fluorescent staining chemicals. “We had no idea that HAP might be involved,” says Prof. Thompson, who is an associate professor of biochemistry and molecular biology at the school. “That’s what makes this work so exciting. It opens up a lot of new research opportunities.”

Click here to read more from the University of Maryland School of Medicine.