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July 1968

Sensorineural Hearing Loss and Congenital Heterochromia Iridum: Report of a Case

Author Affiliations

Vancouver, British Columbia, Canada
From the Department of Paediatrics, University of British Columbia, and the Health Centre for Children, Vancouver General Hospital, Vancouver, British Columbia, Canada.

Am J Dis Child. 1968;116(1):106-109. doi:10.1001/archpedi.1968.02100020108017

PIGMENTATION of the eye is dependent on the formation of melanin from precursors tyrosine or phenylalanine, and the enzyme tyrosinase. In the Negro and Asian races the eye is brown at birth, but in the Caucasian race it is a deep blue color. The change to brown or nonblue variants only occurs if there is a genetic predisposition.

Pigmentation of the iris arises from two sources (Fig 1). Neuroectoderm forms the pigmented epithelium lining the posterior surface of the iris, and extending to form the pigmented layer of the retina. The anterior portion of the iris is of mesodermal origin together with cells which migrate from the neural crest and differentiate into pigmentary cells, melanophores, and sympathetic nervous system tissue. Pigmentation of this part of the iris, which occurs after birth in the white race, occurs later than in the posterior epithelial layer, and appears to require an intact and

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