English: Ultrasound axial scan of the fetal head with eye movements and a monolateral congenital cataract seen at 20 weeks of pregnancy. - The videoclip is a ultrasound scan of the fetal head with the fetal nose pointing upwards and with the fetal orbitae which are bony sockets as round black holes in the skull. Inside the hole you can see normally two white circles (black inside) which are the two lensens of the eye. In this scan you can see that the circle on the left is translucent (black inside) while the cicle on the right side is opaque. The opacity of the lens is by definition a cataract, in this case unilateral, which in the fetus could correlate with cromosomal anomalies, intrauterine infections, genetic conditions, diabetes, trauma, inflammation or drug reactions.