On Mar. 13, 2020, researchers at the National Eye Institute (NEI) reported finding a protein that normally deposits mineralized calcium in tooth enamel may also be responsible for calcium deposits in the back of the eye in people with dry age-related macular degeneration (AMD).

This protein, amelotin, may turn out to be a therapeutic target for the blinding disease. The findings were published in the journal Translational Research. NEI is part of the National Institutes of Health.

There are two forms of AMD – wet and dry. While there are treatments that can slow the progression of wet AMD, there are currently no treatments for dry AMD, also called geographic atrophy. In dry AMD, deposits of cholesterol, lipids, proteins, and minerals accumulate at the back of the eye.

Some of these deposits are called soft drusen and have a specific composition, different from deposits found in wet AMD. Drusen form under the retinal pigment epithelium (RPE), a layer of cells that transports nutrients from the blood vessels below to support the light-sensing photoreceptors of the retina above them. As the drusen develop, the RPE and eventually the photoreceptors die, leading to blindness. The photoreceptors cannot grow back, so the blindness is permanent.

Recently, researchers found a calcium-containing mineral compound called hydroxyapatite (HAP) in dry AMD deposits. HAP is a key component of tooth enamel and bone. Small balls of HAP filled with cholesterol, called spherules, were found only in drusen from people with dry AMD, and not in those with wet AMD or without AMD.