ABSTRACT
Awide variety of congenital malformations may arise during development of the eye. Anomalies may involve a single ocular tissue, a region of the eye, or the entire eye. They may be unilateral or bilateral and may occur in association with a constellation of cranial, facial, or systemic abnormalities. When many tissues are affected, the significance of the associations is not always clear, but a chromosomal/genetic abnormality, an intrauterine infection, or maternal toxin is often involved. Overlapping clinical manifestations from different genetic and non-genetic causes occur as a result of spatial and temporal targeting of specific developmental processes and embryonic events. A growing number of developmental genes, mainly transcription factors and genes involved in signaling pathways, are being identified and their regulatory role(s) in vertebrate eye morphogenesis characterized. Depending on the expression pattern of these genes in different tissues, various organs may be affected, resulting in extraocular manifestions.
