Ultrasonic fetal ophthalmology.

The fetal eye is studied ultrasonically during the second and third trimesters with a large aperture, dynamically focused imaging system. The globe, lens, iris, pupil, and cornea can be resolved separately, and extraocular structures including muscles, retro-orbital fat, and optic nerve may be visualized. The hyaloid artery is seen before 20 weeks and regresses by 25 weeks gestational age. Average vitreous diameter in 157 normal cases exhibits acclerations between 12 and 20 weeks, between 28 and 32 weeks, and near term with decelerations intervening. Associations between limited ocular growth and delayed cerebral development are reaffirmed.