MRI of the fetal eyes: morphologic and biometric assessment for abnormal development with ultrasonographic and clinicopathologic correlation

Background Currently ocular biometric measurements are defined by US and are measured from the orbital walls. These bony landmarks cannot be seen by MRI, and therefore these measurements cannot be directly applied. Objective To define measurements of normal growth of the fetal eyes using MRI. Materials and methods Transorbital views were analyzed in 198 fetal MR examinations. The ocular diameter (OD) and interocular and binocular distances (IOD and BOD) were measured and were plotted against gestational age. Fetuses with abnormalities affecting the eyes were evaluated separately. Results Of 198 scans, 146 had suitable images, 35 of which were abnormal. Normal growth of BOD, IOD and OD were determined, and compared with the respective already established US data. Conclusion Normal growth charts were derived from a cohort of 111 normal fetuses. Because the margins of the vitreous are inside the bony orbit, at the same gestational age measurements of the BOD and OD are always less than the corresponding measurements by US, and those of the IOD are always more. Normal growth charts for MRI can now be used to support suspected diagnoses of orbital and ocular pathologies and the syndromes that give rise to them, and many examples are demonstrated.