Eye abnormalities are present in one-third of inherited, systemic diseases. The presence of a particular ocular sign known to be associated with a systemic disease often is the deciding factor in confirming the diagnosis of that disease. For example, a dislocated lens in the eye can confirm a diagnosis of Marfan syndrome, a connective tissue disease associated with heart problems; a characteristic cherry red spot in the eye usually indicates Tay-Sachs disease.
