Cause of Age-related Macular Degeneration is Linked to Calcium Deposits

Date Posted: 02/27/2015

An international team of researchers led by University College London (UCL) that included individuals from the University of Maryland School of Medicine; Imperial College London; the University of Tubingen, Germany; George Mason University, Fairfax, Virginia; and the University of Chicago have linked age-related macular degeneration (AMD) to calcium deposits in the eye. The researchers hope that this new discovery will lead to significantly earlier detection and eventual treatment for the condition.

When the investigators set out to discover the origin of the build-up in the retina called "drusen" that causes photoreceptors to malfunction in AMD, they found tiny spheres of mineralised calcium phosphate on the retina called "hydroxylapatite" that attracted proteins and fats to their surfaces. The accumulation of these proteins and fats build up over time to form drusen. The researchers identified hydroxylapatites in the eyes of 30 deceased eye donors aged between 43 and 96 years by using fluorescent dyes. "We found these miniscule hollow spheres inside all of the eyes and all the deposits that we examined, from donors with and without AMD," explained the study's leader, Imre Lengyel, senior research fellow at the UCL Institute of Ophthalmology and honorary research fellow at Moorfields Eye Hospital. He further indicated that "eyes with more of these spheres contained more drusen." Since the calcium spheres appear long before drusen becomes visible in a clinical examination, the researchers believe that if a safe technique of injecting fluorescent dye into the eyes of living patients were to be developed, it could help "identify the early signs of drusen build-up long before [it] become[s] visible with current methods," thus advancing "AMD diagnoses by a decade or more. . . ."

In addition, since some of the mineral spheres identified in the eye samples were coated with amyloid beta, which is linked to Alzheimer's disease, if a technique were developed to identify these spheres for AMD diagnosis, it may also assist in the early diagnosis of Alzheimer's. It is unknown whether the calcium spheres are a cause or symptom of AMD, but their discovery could lead to strategies to prevent build-up that could potentially stop AMD from developing altogether. "The calcium-based spheres are made up of the same compound that gives teeth and bone their strength, so removal may not be an option," said Dr. Lengyel. "However, if we could get to the spheres before the fat and protein build-up, we could prevent further growth. This can already be done in the lab, but much more work is needed before this could be translated into patients." For more information, contact: Imre Lengyel, Ph.D., senior research fellow, Department of Ocular Biology and Therapeutics, UCL Institute of Ophthalmology, Room 3/7, Cayton Str Building, ORBIT, 11-43 Bath Street, London, EC1V 9EL, United Kingdom; e-mail: i.lengyel@ucl.ac.uk; website: www.ucl.ac.uk/ioo/departments/orbit.

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