Asteroid hyalosis - External and Internal Eye
The etiology of AH remains unknown, but the opacities are composed of hydroxyapatite-like calcium phosphate complexes and phospholipids. The condition is thought to be degenerative, as it is strongly associated with increasing age. It occurs in only up to 0.2% of people under 55 years of age, while the prevalence in those 75 years or older is 2%-3%. Overall, according to studies in the United States and Australia, AH occurs in about 1% of the population, about twice as often in men as in women, and without any racial predilection. AH has been inconsistently associated with diabetes, hypertension, and dyslipidemia.
AH is asymptomatic in the majority of patients, although large studies detailing the incidence and nature of symptoms (and accounting for conditions which could cause similar symptoms, such as posterior vitreous detachment) are lacking. Although longitudinal data is also lacking, this seems to be a slowly progressive (if not stationary) condition.
H43.20 – Crystalline deposits in vitreous body, unspecified eye
95800001 – Asteroid Hyalosis
- Synchysis scintillans (cholesterolosis) – This condition presents with small, refractile, yellowish, gold, or multicolored cholesterol crystals in the vitreous cavity. This condition generally occurs only in "end-stage" eyes, such as those with a remote history of severe trauma, or with long-standing vitreous hemorrhage. Unlike AH, in which the opacities are suspended (with limited mobility) in the vitreous, the opacities in synchysis scintillans freely float in the vitreous and, with the patient upright, start to settle inferiorly within seconds of cessation of eye movements.
- Vitritis – There are numerous infectious and autoimmune causes of posterior segment inflammation involving the vitreous, and in these conditions, the patient is symptomatic, most commonly with decreased vision and floaters, but not necessarily with pain. He or she may have other signs of ocular inflammation, such as retinal vasculitis, chorioretinal infiltrates, or scleritis. The funduscopic exam exhibits diffuse vitreous haze, with or without focal aggregates of inflammatory cells and fibrinous debris. AH manifests with larger, discrete opacities separated by clear vitreous.
- Vitreous hemorrhage – Due to erythrocyte dehemoglobinization, chronic vitreous hemorrhage may appear as large, well-defined, yellowish opacities, often settled inferiorly due to gravity.
- Amyloidosis (AL amyloidosis, AA amyloidosis) – The autosomal-dominant type of familial amyloidosis (but rarely the more common, nonfamilial amyloidosis) may present with bilateral vitreous opacities, in contrast to AH, which is most often unilateral. Often, other ocular sites are involved, including the eyelids, conjunctiva, and orbit.
- Malignancy – Retinoblastoma (in children), lymphoma, metastatic melanoma, and adenocarcinoma (most commonly of gastrointestinal or pulmonary origin) may occasionally involve the vitreous, but usually choroidal and/or retinal lesions are also present. Sometimes ocular manifestations may precede systemic manifestations of a malignancy.