Asteroid Hyalosis
Asteroid hyalosis commonly affects individuals over the age of 50, with an incidence rate of approximately 1 in 200. Seventy-five percent of cases occur in only one eye, and the condition is more prevalent among individuals with diabetes compared to those without diabetes. The primary constituents of the vitreous opacities are fatty acids and calcium phosphate salts. Clinically, it generally presents without significant symptoms and rarely affects visual acuity. Fundus examinations showcase scattered yellow-white particles of varying sizes within the vitreous, which contain calcium lipids. Asteroid hyalosis differs from synchysis scintillans in several aspects: it typically occurs in a single eye, there is no liquefaction of the vitreous, and when the eye abruptly stops moving, the small white dots shift slightly and return to their original position rather than settling at the bottom of the vitreous cavity. No specific treatment is typically required.
Synchysis Scintillans
Synchysis scintillans, also referred to as vitreous cholesterolosis, is less common compared to asteroid hyalosis and is usually bilateral. Microscopic and chemical analysis of the vitreous opacities reveals cholesterol crystals. The etiology remains unclear, and it most frequently occurs before the age of 40. This condition is associated with traumatic injury to the vitreous or post-surgical complications involving significant intraocular bleeding. Clinically, it is asymptomatic and does not cause significant changes in visual acuity. Eye examinations, particularly with a slit lamp microscope or ophthalmoscope, reveal small yellow-white, golden, or multicolored cholesterol crystals located within the vitreous or anterior chamber. When the eye moves, the opacities freely drift within the liquefied vitreous cavity, and they settle at the bottom when the eye remains still. Synchysis scintillans is often accompanied by posterior vitreous detachment and needs to be differentiated from asteroid hyalosis. No specific treatment is generally required.