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Orbital hypertelorism is defined as excessive separation of the medial walls of the bony orbit. This dimension should always be considered in relationship to overall head size, since excessive spacing of the orbits in a head greater than two standards above the mean may be considered normal. After birth, radiological assessment of the bony interorbital distance is the most accurate method to determine whether excessive eye spacing is present. However, interpupillary distance is the optimum dimension used in clinical determination of eye-spacing. This measurement may have ultrasonographic relevance in the future, particularly as a transvaginal approach allows visualisation of the fetal lens. During early embryonic life, the eyes grow laterally on optic stalks, and then move towards the midline. Several mechanisms have been proposed to explain the development of orbital hypertelorism. Firstly, there may be morphokinetic arrest that causes failure of migration of the orbits to the midline with some time-specific deficiency in differential growth. Secondly, interruption of migration might occur because a primary midline lesion, such as an encephalocele, inhibits approximation of the orbits. Thirdly, a pathological process affecting the cranial base, for example, secondary to craniosynostosis, could lead to separation of the orbits.


Although orbital imaging is not routine in most centres, and is not included in the AIUM guidelines for obstetrical ultrasonography, the bony orbits are reliably imaged when scanning the fetal face from the 12th week onward. Care must be taken to avoid tangential cuts through the orbits. The inner orbital measurement is most useful in the determination of hypertelorism, and is generally greater than two standard deviations from the mean. The outer orbital measurement often falls at the 95th percentile. With the head in the occipitotransverse position, the transducer can be placed in two possible planes, firstly, along the coronal plane, approximately 2 cm posterior to the glabella-alveolar line, or, secondly, along the orbitomeatal line, approximately 2 to 3 cm below the level of the biparietal diameter. In both these views, the midline, orbital rings, nasal processes, and portions of the maxilla can be demonstrated. The inner and outer orbital diameters are measured from the leading edge to falling edge; outer diameter from lateral border of one bony orbit to lateral border of the other bony orbit, inner diameter from medial border to medial border. Occasionally, when the head is in this position, it is difficult to define accurately the distal orbital margin because of acoustic shadowing from the nose. With the head in the occipitoposterior position, a biparietal diameter cannot be obtained. However, the orbits can be identified and measured with the transducer placed in a plane that transects the occiput, orbits and nasal processes. Measurements should only be obtained when the fetal face is perpendicular to the uterine wall, since measurements in an oblique plane may be unreliable. The optimal view of the fetal eyes on transvaginal ultrasonography is a transverse section of the fetal skull at the orbital plane. The eyes within the bony orbits are detected as bilateral hypoechoic circles superolateral to the nasal bones. A detailed search for intra- and extra-cranial anomalies should be performed since these are frequently associated with differences in eye spacing, and may provide evidence for a particular malformation syndrome, as detailed in the table of associated syndromes. Prenatal diagnosis has been reported in Opitz, Crouzon , Apert and median cleft face (frontonasal dysplasia) syndromes.

Differential Diagnosis:

Primary hypertelorism, due to lack of convergence of the bony orbits, should be differentiated from hypertelorism secondary to a midline lesion, such as a frontal encephalocele.

Sonographic Features:

Inner orbital distance greater than two standard deviations above the mean for gestational age. Often accompanied by outer orbital distance at the upper limits of normal


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1 Hypertelorism

Associated Syndromes

Aminopterin -like syndrome without aminopterin (ASSAS)
Chromosome anomaly
Frontofacionasal dysplasia
Frontonasal dysplasia
Hypertelorism-Microtia clefting
Opitz [G, BBB]
Teratogen exposure


Hypertelorism, microtia and facial clefting: a newly described, inherited syndrome
Bixler D
Am J Dis Child 118: 495-8

Craniofrontonasal dysplasia
Cohen MM Jr
Birth Defects 15: 85-9

The facial profile in the diagnosis of fetal abnormalities
Turner GM, Twining P
Clin Radiol 47: 389-395

In: Human Malformations and Related Anomalies
Traboulsi E
Oxford University Press, p634-8

First- and second-trimester diagnosis of fetal ocular and associated anomalies: report of eight cases
Bronshtein M, Zimmer E, Gershoni-Baruch R, Yoffe N, Meyer H, Blumenfeld Z
Obstet Gynecol 77: 443-9

An aminopterin-like syndrome without aminopterin (ASSAS)
Fraser FC, Anderson RA, Mulvihill JI, Preus M
Clin Genet 32: 28-34

Orbital diameters: a new parameter for prenatal diagnosis and dating
Mayden KL, Tortora M, Berkowitz RL, Bracken M, Hobbins JC
Am J Obstet Gynecol 144: 289-297

Interstitial deletion of chromosome 1 del (1) (q32q42): case report and review of the literature
Sarda P, Lefort G, Taviaux S, Humeau C, Rieu D
Clin Genet 41: 25-7

Teebi hypertelorism syndrome: report of a third family
Toriello HV, Delp K
Clin Dysmorph 3: 335-9

Ocular findings in Turner syndrome: a prospective study
Chrousos GA, Ross JL, Chrousos G, Chu FC, Kenigsberg D, Cutler G Jr, Loriaux DL
Ophthalmology 91: 926-8

Diaphragmatic hernia, exomphalos, absent corpus callosum, hypertelorism, myopia, and sensorineural deafness: a newly recognised autosomal recessive disorder?
Donnai D, Barrow M
Am J Med Genet 47: 679-682

Significance of orbital measurements in the fetus
Trout T, Budorick NE, Pretorius DH, McGahan JP
J Ultrasound Med 13: 937-43

Letter to the editor: Frontofacionasal dysostosis - a new autosomal recessive syndrome
Gollop TR
Am J Med Genet 10: 409-412

Iris coloboma, ptosis, hypertelorism, and mental retardation: a new syndrome possibly localised on chromosome 2
Pallotta R
J Med Genet 28: 342-4

Antenatal diagnosis of median cleft face syndrome: sonographic demonstration of cleft lip and hypertelorism
Chervenak FA, Tortora M, mayden K, Mesologites T, Isaacson G, Mahoney MJ, Hobbins JC
Am J Obstet Gynecol 149: 94-7

Sonographic appearance of craniofacial dysostosis (Crouzon syndrome) in the second trimester
Gollin YG, Abuhamad AZ, Inati MN, Shaffer WK, Copel JA, Hobbins JC
J Ultrasound Med 12: 625-8

Oral and dental development in X chromosome aneuploidy
Farge P, Dallaire L, Albert G, Melancon SB, Potier M, Leboeuf G
Clin Genet 27: 122-6

Hirschsprung disease associated with polydactyly, unilateral renal agenesis, hypertelorism, and congenital deafness: a new autosomal recessive syndrome
Santos H, Mateus J, Leal MJ
J Med Genet 25: 204-8

Hypertelorism in neurofibromatosis
Wolters EC, Westerhof W, Delleman JW, Dijkstra P
Neuropediatr 17: 175-7

Fetal ocular biometry by ultrasound
Jeanty P, Dramaix-Wilmet M, Van Gansbeke D, Van Regemorter N, Rodesch F
Radiology 143: 513-6

Prenatal diagnosis of Opitz (BBB) syndrome in the second trimester by ultrasound detection of hypospadias and hypertelorism
Hogdall C, Siegel-Bartelt J, Toi A, Ritchie S
Prenat Diagn 9: 783-793

Iris coloboma, ptosis, hypertelorism, and mental retardation: a new syndrome
Baraitser M, Winter RM
J Med Genet 25: 41-3

Apert syndrome, an antenatal ultrasound detected case
Parent P, Le Guern H, Munck MR, Thoma M
Genetic Counselling 5: 297-301

New X-linked syndrome of mental retardation, short stature, and hypertelorism
Stoll C, Geraudel A, Chauvin A
Am J Med Genet 39: 474-8

Prenatal diagnosis: evolution in craniofacial surgery.
De Ponte FS; Bottini DJ; Maggi E; Marchetti E; Cascone P; Iannetti G
J Craniofac Surg Mar;9(2):190-5

A new craniofacial disorder involving hypertelorism and malformations of external nose, palate and pituitary gland.
Kjaer I; Reintoft I; Poulsen H; Nolting D; Prause JU; Jensen OA; Fisher Hansen B
J Craniofac Genet Dev Biol Jan-Mar;17(1):23-34