Fetal eye movement assessed with real-time ultrasonography: are there rapid and slow eye movements?

Abstract

The goal of this study was to determine whether rapid eye movement and slow eye movement exist during the eye-movement period in the human fetus in utero. We studied 21 fetuses with real-time ultrasonography, 10 from 33 to 36 weeks and 11 from 37 to 41 weeks' gestation. We used the duration of eye-movement unit as a parameter and calculated the cumulative duration from the shortest to a given duration of eye movement per individual case. A scattergram of cumulative duration versus given duration obtained from all cases in each age group was analyzed with piecewise linear regression to search for a critical point(s). Critical given duration points were noted and reached statistical significance at 0.62 second and at 0.76 second during 33 to 36 and 37 to 40 weeks of gestation, respectively. These findings reveal two different types of eye movement: one with a duration of less than 0.6 to 0.8 second and the other with a duration of greater than 0.6 to 0.8 second. These findings are compatible with previous criteria on rapid and slow eye movements, respectively, at 33 weeks of gestation onward. The mean value of cumulative duration at the critical point increased from 29.0% between 33 and 36 weeks to 47.1% between 37 and 41 weeks of gestation, indicating an increase in the proportionate amount of time maintaining rapid eye movement as gestation advances.