Asteroid Hyalosis

Two views of asteroid hyalosis.

Signs and symptoms: Asteroid hyalosis is a primarily unilateral disorder that typically occurs in patients over 60 and in men twice as often as women. Usually asymptomatic, in severe cases asteroid hyalosis can mildly affect visually acuity. Complaints of floaters are a rarity.

Ophthalmoscopically, asteroid hyalosis appears as multiple, discrete, refractile yellow or yellow-white particles suspended in the vitreous. In early stages, there are fewer bodies and they accumulate in the inferior vitreous. Advanced cases can be so dense as to impair your view of the posterior fundus. In whites the prevalence of asteroid hyalosis is 1-2%, and it is bilateral in about 10% of cases.¹ This prevalence seems to increase with age.

Pathophysiology: Asteroid bodies represent small calcium-laden lipids suspended within and attached to the hyaluronic acid framework of the vitreous body. While we understand the composition of the asteroid bodies, the exact genesis remains unclear. Current theories suggest that asteroid hyalosis results from aging collagen within the vitreous or a depolymerization of hyaluronic acid.

Management: Asteroid hyalosis is a benign condition in itself. Although it progresses, it never leads to severe vision loss, and the mild symptoms occur rarely. The vast majority of cases merely require documentation. More often than not, this disorder poses a greater challenge to the examining physician because it can obscure details of the underlying retina. Consider treatment only in patients who are also being managed for retinal disease (proliferative diabetic retinopathy, retinal tear or detachment). Vitrectomy is typically indicated in these instances.

Clinical Pearls:

• Asteroid hyalosis presents a picture akin to "stars in the night sky." On eye movement, the asteroid bodies sway within the vitreous, but always return to their original position.
• Synchisis scintillans and amyloidosis are often confused with asteroid hyalosis.
• Synchisis scintillans (cholesterol bulbi) is an extremely rare condition that occurs in severely diseased eyes. This condition also presents with refractile crystals in the vitreous, although these particles are composed of cholesterol. They are not attached to the vitreal framework, so they tend to settle out inferiorly after eye movement. Because this condition occurs in end-stage eye disease, pathologists rather than clinical optometrists or ophthalmologists typically make the diagnosis of synchisis scintillans.
• Amyloidosis of the vitreous is also quite rare, and occurs typically after age 40. Patients characteristically demonstrate bilateral involvement with granular, strand-like opacities within the central vitreous. These membranes are anchored to the posterior lens surface in about half of patients. Small, yellow-white bodies dot the vitreal strands.
• Remember that the density of asteroid hyalosis does not correlate with visual dysfunction. If a patient presents with significantly diminished acuity, asteroid hyalosis is not to blame.
• Patients with asteroid hyalosis and an unknown medical status require evaluation for diabetes, hypertension, hyperlipidemia and atherosclerotic vascular disease.
• Filters used for performing fluorescein angiography can allow a better fundus view through the retinal camera in cases of severe asteroid hyalosis and may allow you to observe pathologies that conventional ophthalmoscopy does not reveal. 

1. Moss SE, Klein R, Klein BE. Asteroid hyalosis in a population: the Beaver Dam eye study. Am J Ophthalmol 2001 Jul;132(1):70-5.