Retinal coloboma is an important cause of childhood visual impairment and blindness. It may be isolated or associated with one of several syndromes. To our knowledge, prenatal diagnosis of the condition has only been reported previously using magnetic resonance imaging, in a small number of cases1. We report a case of fetal coloboma diagnosed prenatally using a new three-dimensional (3D) ultrasound technique, the ‘virtual fetal eyeground’. A 23-year-old primigravida was examined in our institution at 27 weeks after right fetal microphthalmia had been diagnosed at 22 weeks. A careful examination of both eyes with two-dimensional ultrasound imaging revealed a small notch on the bottom of the left eyeball (Figure 1), leading to suspicion of a small coloboma of the retina. We then performed a 3D transabdominal ultrasound examination using a new technique, the ‘virtual fetal eyeground’, to visualize the left retina. Two-dimensional ultrasound image of the left eye at 27 weeks, showing the small notch on the bottom of the eyeball (arrow) that led to suspicion of a coloboma of the retina. Using a Voluson E8 (GE Medical Systems, Zipf, Austria) equipped with a transabdominal 5–9-MHz probe, volumes of the entire eye were acquired in a frontal plane of the fetal face. After volume acquisition, surface rendering mode was applied and the ‘Magicut’ tool was used to ‘erase’ the frontal portion of the eyeball, enabling visualization of the entire retina in a manner similar to an eyeground examination after birth2. Using this technique, a ‘hole’ (or coloboma) in the central part of the retina at the level of the papilla measuring 2.6 mm × 2.1 mm was diagnosed (Figure 2a; a normal retina at the same gestational age is shown in Figure 2b). The diagnosis was confirmed by an ophthalmologic examination under anesthesia 1 month after birth (Figure 3). (a) Visualization of the fetal coloboma at the level of the papilla at 27 weeks using a new three-dimensional ultrasound technique, the ‘virtual fetal eyeground’, and (b) a normal retina visualized using the technique at the same gestational age. Ophthalmoscopic image of the retina with coloboma at 1 month after birth. Development of the eyes begins with the formation of the optic sulcus at 22 days' gestation in the region of the future diencephalon. The cranial neuropore closes on day 24 and by this time the optic primordia have developed into lateral evaginations of the neural tube, the optic vesicles. The distal face of the optic vesicle (retinal disc) invaginates into the expanded tip of the optic vesicle to form the optic cup on day 31, which is connected to the brain via the optic stalk. Blood vessels access the interior of the optic cup via a groove on its ventral surface, the choroid fissure. The lips of the choroid fissure fuse by day 37, and the persistence of a part of the choroid fissure may be a cause of colobomas. Colobomas may occur in different parts of the eyeball: the eyelid, iris, retina and optic nerve3-6. The ‘virtual eyeground’ technique permits visualization of the entire retina from 16 weeks' gestation onwards2. We believe it may have a role in the diagnosis of retinal injury in isolated microphthalmia, and of fetal syndromes7-9 involving abnormalities of the eye such as CHARGE and PHACE10-12. We are grateful to Professor D. Bremond-Gignac (of the Department of Pediatric Ophthalmology) for examining the infant after birth and providing the ophthalmoscopic image.