Introduction In utero eye development as seen by fetal magnetic resonance imaging (MRI) has not been well described. Fetal MRIs are becoming a more frequently used modality to complement the findings of prenatal sonograms when an abnormality of the fetus is suspected. To date, very little attention has been given to ocular abnormalities that may be detected by fetal MRI. Our objective in this preliminary study was to document normal eye development in the human fetus.
Methods We retrospectively reviewed 27 fetal MRIs (54 eyes) and recorded the transverse diameter of each globe, the intraocular distance, and the lens diameters and calculated the volume of each globe. Means and standard deviations for each measurement were stratified by gestational age. All fetal MRIs at our institution were eligible for inclusion in the study. Images were reviewed randomly. All gestational ages were included. Patients were not excluded if they had congenital anomalies. Films that included artifact so severe to distort the orbital images were excluded. Using a 1.5-Tesla magnet, a body coil was placed over the mother's abdomen and multiple single-shot T2 fast spin echo images were obtained using 3 mm collimation. The images were of axial, sagittal, and coronal planes of the fetus. Quantitative measurements were performed on a Synapse PACS.
Results The transverse diameter of the globe appears to follow a linear growth curve, ranging from averages of 7.35 mm at 17 weeks' gestation to 16.67 mm at 37 weeks' gestation. The growth curve for intraocular distance is similar, with a range of 9.95 mm at 17 weeks' gestation to 17.44 mm at 37 weeks' gestation. It appears that lens growth increases more rapidly toward the latter part of gestation, with little change between 17 and 28 weeks' gestation (2.65-2.71 mm) compared with the measurement at 37 weeks of 5 mm. Orbital volume increases dramatically between 24 and 28 weeks' gestation (average volume 388 mm3 at 17 weeks, 661 mm3 at 23 weeks, and 1,610 mm3 at 28 weeks).
Conclusion These data provide baseline establishment of growth curves for eye globe transverse diameter, intraocular distance, lens diameter, and globe volume. These measurements may be useful in cases with suspected congenital orbital abnormalities.
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