Asteroid hyalosis: pathogenesis and prospects for prevention

Asteroid hyalosis (AH) is a common degenerative process in which fatty calcium globules collect within the vitreous humour. The condition rarely causes visual disturbances, and surgical removal is only rarely required. The presence of AH has been associated with systemic diseases such as diabetes; however, research in this area has been hampered by the lack of an animal model of AH. Recently, we have reported that AH occurs in galactose-fed beagles that develop the advanced stages of diabetes-like retinopathy. Comparisons of vitreous humour containing asteroid bodies (ABs) collected from these galactose-fed beagles and vitreous samples from age-matched normal beagles without ABs indicate that ABs contain calcium and phosphorous. Subtraction analysis of chloroform extracts of the vitreous samples by electrospray mass spectroscopy resulted in the identification of the quasimolecular ion of 1,2-dipalmitoyl-glycero-3-phosphoethanolamine (DPPE) as the main component of ABs. Since several reports indicate that ABs are composed of lipid-calcium complexes, we have proposed that the main component of ABs in the galactose-fed dogs with AH is a quasimolecular ion of DPPE in which two molecules of DPPE are complexed through their phosphates groups with calcium. We suggest that these lipid components diffuse into the vitreous from the degenerating retinas of these dogs.