Changes in pupillary diameter in relation to eye-movement and no-eye-movement periods in the human fetus at term.

OBJECTIVE

The aim of our study was to reveal whether pupils dilate and constrict in a time sequence in the human fetus and to assess the relationship between changes in pupillary diameter and eye-movement-no-eye-movement periods.

STUDY DESIGN

We simultaneously observed pupil and eye movement with real-time ultrasonography in 30 human fetuses at 36 to 41 weeks' gestation. Eighteen were excluded because of data loss. Statistical analysis of pupillary diameter changes were made on the remaining 12 fetuses with the least median of squares regression.

RESULTS

Pupillary diameters were found to be differentiated with statistical significance into two groups: 9.7% for the dilated pupil (median 3.0 mm) and 90.3% for the constricted pupil (1.7 mm). The percentage of dilated pupils during the eye-movement period (14.3%) was significantly greater than that during the no-eye-movement period (2.3%; Wilcoxon rank sum test, p < 0.0001).

CONCLUSION

These findings indicate a close relation between pupillary dilatation and eye-movement periods in the human term fetus.