Functional development of human eye movement in utero assessed quantitatively with real-time ultrasound.

Functional development of eye movement in the human fetus in utero was assessed quantitatively, with real-time ultrasound. A pair of lens-derived echoes was used as a landmark to evaluate positional deviation with eye movement. The frequency of eye movement was measured either with 1-minute continuous observations or at 1-minute cross sections. Two hundred forty-five normal fetuses between 18 and 42 weeks of gestation were studied. Three critical ages, with respect to physiologic development of fetal eye movements, were evident: 22 to 25, 30 to 33, and 38 to 41 weeks. The first and the second indicate the onset of the moderate-frequency and high-frequency eye movements, thereby implying a transition, presumably to a state of so-called rapid eye movement and a rise of rapid eye movement, respectively. The third represents full maturation of the mechanisms, that is, non-rapid eye movement and rapid eye movement.