Tiny lumps of calcium phosphate may be an important triggering factor for age-related macular degeneration (AMD), according to scientists at the University of Maryland School of Medicine (UM SOM). AMD is a degenerative eye disease that can cause severe vision loss and blindness.

Previous studies have shown that 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. But, the origins of these deposits remained a mystery.

The research team studied retinal samples using X-ray diffraction and fluorescent staining chemicals from a group of elderly patients, some of whom had AMD. They found that the AMD samples contained tiny spherules of mineralized calcium phosphate known as hydroxyapatite, or HAP that comprises the hard part of bones and teeth, and had never been identified in that part of the eye before. Once these HAP chunks appear, the fatty protein material coalesces around it; over years, these globules build up. Researcher Imre Lengyel said, "We think HAP plays a key role in this process. This is a new explanation for how these deposits start."