A fetal neuroscan is not complete without a thorough examination of the orbits, the eyes, and their surroundings.
Malformations of the eyes can be solitary or in association with other anomalies. Therefore, a search for those should be undertaken.
Any alteration in the shape or size of the orbits, the interorbital distances should be evaluated as a possible sign of other anomalies.
Whenever fetal position enables, transvaginal sonography should be used.
The ultrasonographic examination of the eyes is an important and integral part of the fetal face survey. This chapter describes the methodology of the orbit and eye evaluation, the ultrasonic landmarks of the normal eye, and the features of congenital abnormalities that may be detected in the fetus. The presented data are a summary of the English literature on this topic, as well as the authors' experience.
EPIDEMIOLOGY OF CONGENITAL BLINDNESS
Congenital blindness is a common disorder in developing countries in contrast to Western countries.1,2,3,4 Robinson and coworkers1 reported a prevalence of 3 per 10,000 births for eye malformations in British Columbia. Stoll and associates4 found congenital eye malformations in 7.5 per 10,000 births in France. Studies in Great Britain5,6 have shown that about half of the cases of childhood blindness are genetically determined. Twenty percent of all cases were autosomal dominant, 17% autosomal recessive, 5% X-linked, and 8% were thought to be multifactorial.5 Intrauterine infections such as rubella and toxoplasmosis are also regarded as major factors contributing to eye malformations. More recently, fetal alcohol syndrome has become well recognized as a cause of ocular abnormalities, particularly of optic nerve hypoplasia.5,7
The most commonly described ocular abnormalities were cataract (30%), microphthalmia (24%), coloboma (9%), and anophthalmia (4%).1,4,5 Robinson et al1 and Phillips et al6 also reported that cataract was the most common eye abnormality associated with congenital blindness.
As extending the previous study performed in France, Stoll et al,7 reporting on 212,479 deliveries, found a slightly lower prevalence of congenital eye malformations of 6.8 per 10,000. In this study, the prevalence of cataract was 2.7/10,000; of microphthalmia, 1.7/10,000;7 of anophthalmia, 0.23/10,000; and of coloboma, 1.4/10,000.5 Associated fetal anomalies included clubfeet, microcephaly, hydrocephaly, cleft lip and palate, and facial dysmorphism.7 The affected neonates were smaller, weighed less, had smaller head circumference and lower placental weight, and were more often complicated by threatened abortion or oligo- or polyhydramnios than controls.7 Their mothers more often used drugs during pregnancy, and their fathers were more often exposed to occupational hazards than fathers of controls.7 Eye malformations were associated with parental consanguinity.7 The recurrence risk for first-degree relatives of probands was 8.9%;7 this risk was more than 3 times that for additional, nonocular malformations.7