Eye findings in patients with phenylketonuria

Untreated phenylketonuria (PKU) is characterized by excretion of phenylpyruvic acid in the urine and mental retardation. Reported eye abnormalities include photophobia (probably due to the albinoid iris), cataracts, and corneal opacities. Eleven patients in an institutionalized population of approximately 1,000 mentally retarded patients had PKU. Cataracts were found in six patients. One patient had bilateral phthisis bulbi and one patient had monocular phthisis. No corneal opacities were found otherwise. All patients with cataracts were middle-aged or had a history of severe self-induced trauma or treatment with high dosages of thioridazine hydrochloride. Albinism is associated with anomalous chiasmal routing of optic fibers and abnormal, extraocular motility. The ocular hypopigmentation of patients with PKU did not have the same results; all seeing patients were orthophoric. Although eye abnormalities are common in PKU except for hypopigmentation, none can be considered a direct effect of the inborn error of metabolism.