© 2008 by Informa Healthcare USA, Inc. Of the many genetic disorders that express themselves as specific defects of amino acid metabolism, some, including two of Garrod’s four original “inborn errors of metabolism” (albinism, alkaptonuria), produce significant abnormalities in the ocular tissues (92). Several abnormalities in the metabolism of the essential amino acid phenylalanine and its oxidized derivative tyrosine are recognized. From the standpoint of the eye, albinism, alkaptonuria, and tyrosinemia are the most important.