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. 2021 Oct;11(10):4389-4398.
doi: 10.21037/qims-21-151.

Dimensions of the optic chiasm: quantitative ultrasound comparison between fetuses with anophthalmia/microphthalmia and normal fetuses

Li-Hong Wu  1 , Qiao Zheng  1 , Miao He  1 , Li-He Zhang  1 , Liu Du  1 , Hong-Ning Xie  1
Affiliations

Dimensions of the optic chiasm: quantitative ultrasound comparison between fetuses with anophthalmia/microphthalmia and normal fetuses

Li-Hong Wu et al. Quant Imaging Med Surg. 2021 Oct.

Erratum in

Abstract

Background: The precise pathogenesis of anophthalmia/microphthalmia remains unknown. Prenatal observation of the optic chiasm in fetuses with this malformation would assist in understanding the embryonic development of the condition. The present study aimed to establish the normal fetal size ranges of decussation of the optic chiasm, optic nerves, and optic tracts in the axial plane using two-dimensional transabdominal ultrasound throughout gestation and to compare these ranges to the corresponding values in fetuses with anophthalmia/microphthalmia.

Methods: In total, 310 normal fetuses and 16 fetuses with anophthalmia/microphthalmia were included in this study. The widths of the decussation of the optic chiasm, optic nerves, and optic tracts of normal fetuses at 19-40 weeks' gestation were measured in the axial plane by two-dimensional transabdominal ultrasound. The same widths were retrospectively measured in the axial plane using three-dimensional ultrasound in fetuses with anophthalmia/microphthalmia and compared to the results from the normal fetuses.

Results: The decussation, optic nerves, and optic tracts of 310 normal fetuses were measured. The normal widths of the decussation of the optic chiasm, optic nerves, and optic tracts increased linearly with gestational age. The interobserver and intraobserver reproducibility was excellent for the decussation but relatively low for the optic nerves and optic tracts. The optic nerve width of fetuses with anophthalmia/microphthalmia was significantly smaller than that of normal fetuses (P<0.001), but the widths of the decussation (P=0.061) and optic tracts (P=0.053) were not significantly different between the two groups.

Conclusions: The normal ranges of the decussation of the optic chiasm, optic nerves, and optic tracts established in this study can provide a quantitative basis for prenatal evaluation of the optic pathway. Fetal anophthalmia/microphthalmia may be associated with optic nerve hypoplasia.

Keywords: Prenatal diagnosis; anophthalmia; microphthalmia; optic chiasm; ultrasound.

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Conflict of interest statement

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/qims-21-151). The authors have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Two-dimensional transabdominal ultrasound image showing the measurement of a normal optic chiasm width in the axial plane for a 28+5-week fetus. (A) The measurement of the decussation width, (B) the measurement of the optic nerve width, (C) the measurement of the optic tract width.
Figure 2
Figure 2
Three-dimensional ultrasound image and pathology specimens showing the optic chiasm in the axial plane for a 22+2-week fetus with unilateral microphthalmia (Case 4). (A) Sonograms showing a normal-shaped decussation (arrows). (B) Sonograms showing that the left side optic nerve (arrow) is visible, but the right side optic nerve is invisible. (C) Sonograms showing bilateral normal-shaped optic tracts (arrows). (D) Pathology specimens showing the right microphthalmia (white*) and ipsilateral delicate optic nerve (white arrow), and the left normal-shaped eye (black *) and optic nerve (black arrow).
Figure 3
Figure 3
The flowchart of inclusion criteria for fetuses with anophthalmia/microphthalmia.
Figure 4
Figure 4
Plots showing the distribution of (A) the decussation, (B) optic nerve, and (C) optic tract in fetuses with anophthalmia/microphthalmia (△) and normal fetuses (●). In (A-C), horizontal lines show the normal mean and 95% range.
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