Ocular findings in conjoined (Siamese) twins.

Conjoined twinning is a rare form of congenital anomaly. The ocular findings in six sets of conjoined twins as well as those reported elsewhere include abnormal optic nerve decussation, pseudosynophthalmos, microphthalmia, abnormal eyelids, orbital encephalocele, occipital encephalocele, and eyelid coloboma. These findings are interpreted as due to deformations from appositional fusion-related factors or malformations from developmental factors.