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KEY POINTS
The neurosonographic examination is not complete without a thorough examination of the orbits, the eyes and their surroundings.
Malformations of the ocular system can be solitary or in association with other anomalies. Therefore, a search for those should be undertaken in the presence of suspected fetal ophthalmic findings.
Especial attention should be dedicated to the size and shape of the orbits and to the intrerorbital distance as common signs of the presence of more serious anomalies.
Whenever possible, particularly early in pregnancy, TVS provides a more accurate visualization of the eye structures.
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The fetal eye primordium starts development by the 22nd postconceptional day when the forebrain neural fold extends laterally to form the optic vesicles1,2 (Figure 19–1). Critical steps during eye development are the formation of the eye field, specification of the neural retina and retina pigment epithelium (RPE), proliferation, neurogenesis, lamination and development of retinal connectivity, differentiation of the lens, ciliary body and iris, as well as vasculogenesis.1 Developmental disruptions at any of these steps can result in severe eye defects and in blindness.
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The visualization of the orbits and lenses is considered an integral part of the anatomic examination of the fetuses. Although routinely performed during the second trimester, it is possible to study the eye anatomy starting from the late first trimester; by this time the development of the main ocular structures is completed, making possible the diagnosis of some congenital eye malformations. The diagnosis of other developmental malformations, particularly these involving the size of the orbits and insults to the eye, may remain undiagnosed until late in pregnancy or after delivery.
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INCIDENCE AND PREVALENCE
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Studies on the epidemiology of congenital ophthalmologic conditions report different results depending on geographical areas, social status, and type of study performed.
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One the largest studies on the epidemiology of congenital eye malformations was published more than 20 years ago by Stoll et al, and included the follow-up during the period between 1987 and 1994 of 212,479 children in Strasbourg, France; the authors diagnosed 145 affected children.3 The overall prevalence for congenital eye malformations was 6.8 per 10,000; the most common malformation was cataract (2.7/10,000) followed by micro/anophtalmia (2.2/10,000) and coloboma (1.4/10,000)
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Eye malformations were found to be associated with other malformations in 54% of the cases. A prenatal diagnosis was reached in only 18 cases.3
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More recently, a larger study from England based on cases referred for the first time to a health facility with eye malformations found that ...