Fetal ocular measurements by three-dimensional ultrasound

Purpose: To establish a reference range for normal fetal eye volume (FEV) by three-dimensional ultrasound using Virtual Organ Computer-aided AnaLysis (VOCAL) method and compare the reproducibility between the two trace modes (manual and sphere).

Methods: This prospective, longitudinal observational study was performed at a single center and involved 71 eyes of 37 fetuses between 17 and 40 weeks of gestational age. Only pregnancies without fetal growth restriction, diabetes mellitus, hypertension, or major fetal malformation were included. Fetuses' eye measurements were obtained by a single observer during routine ultrasonographic examination.

Results: Mean FEV manual mode ranged from 309.5 ± 80.1 mm(3) at 17-18 weeks to 2552.1 ± 384.9 mm(3) at 39-40 weeks. Mean FEV sphere mode ranged from 394.8 ± 71.8 mm(3) at 17-18 weeks to 2682.1 ± 343.4 mm(3) at 39-40 weeks. Correlations ranged from R² = 0.85 (transversal diameter and gestational age) to R² = 0.91 (FEV sphere mode and gestational age). All correlations were statistically significant (P < 0.001). Although highly correlated (R² = 0.97, P < 0.001), there was a fixed bias between manual and sphere measurements. The agreement between these measurements showed no proportional bias (P = 0.89).

Conclusions: The present study establishes reference values for FEV using the VOCAL method manual mode. These normal growth parameters can be used in routine ultrasound assessment of the fetal eye, especially in families at risk of genetic diseases that affect ocular growth, such as congenital glaucoma.