Telecanthus: increased distance between the medial canthi. The inter-orbital distance is normal.
Hypertelorism: increased distance between the orbits.
Orbital hypertelorism signifies an increased distance between both medial sides and lateral sides of the orbits.
Interorbital hypertelorism(bony telecanthus) denotes increased distance only between the inner orbital walls.
Interorbital hypertelorism - interorbital distance more than 2 standard deviations from normal mean, age and gender matched, with a normal outer orbital distance.
Orbital hypertelorism - both interorbital and outer orbital distances of more than 2 standard deviations from the normal mean
Orbital hypertelorism occurs during the period prior to the 28-mm C-RL stage(approximately 50 days) of embryonic development.
The anomaly is not lateralization but failure of medialization of the entire orbits.
In contrast, interorbital hypertelorism more likely occurs during the period following medialization of the orbits.
A localized(field) defect(s) or sequence leading to abnormal development of the frontonasoethmoid complex could prevent primary medialization or cause excessive secondary lateralization of the medial orbital walls.
Assessment of Interorbital Distance
Inter-pupillary distance (IPD) unreliable because varies with extraneous conditions, eg squint. Inter-orbital distance should be used.
IOD – measured radiographically; the shortest distance between the medial walls of the orbits at approximately the level of the junctions of each medial angular process of the frontal bone with the maxillary and lacrimal bones.
the distance between the dacrya (dacryon = junction of frontal lacrimal bones), i.e., the interorbital distance
the distance between the lateral orbital rims at the horizontal level of the dacryon, i.e., the outer orbital distance.
Hypertelorism refers to increased interorbital distance
orbital hypertelorism - both interorbital and outer orbital distance increased
interorbital hypertelorism - interorbital distance increased but normal outer orbital distance.
At birth, IOD = 16mm; at 12 years, IOD = 25mm; in adults, the normal inter-orbital distance is 25 mm in women and 28 mm in men.
1st degree hypertelorism: IOD = 30-34 mm
2nd degree hypertelorism: IOD = 35-40 mm
3rd degree hypertelorism: IOD > 40 mm
Gunther/Tessier based on standard deviation (SD)
first degree, interorbital distance 2 to 4 SDs
second degree, 4.1 to 8 SDs
third degree, more than 8 SDs greater than the normal mean.
Can also be classified according to the configuration of the medial orbital wall: parallel, divergent, bulging or convergent. The last 2 are the rarest and most difficult to Rx.
most common cause of hypertelorism
also known as Median Cleft Face Syndrome, Frontonasal Syndrome, Frontonasal Dysplasia
symmetrical, orbital type hypertelorism
median cleft or bifid nose, median cleft upper lip and premaxilla, median cleft palate, widow's peak, anterior cranium bifidum occultum
(Above, left) Facies A: frontonasal malformation in a 4-year-old girl. Note the symmetrical second-degree interorbital hypertelorism, prominent widow's peak, and broad bifid nasal tip. She had resection of a nasal dermoid that extended intracranially.(Above, center) Facies B: frontonasal malformation (minor) with bipartate nasal tip and second-degree interorbital hypertelorism.(Above, right) Facies B: frontonasal malformation (major) in a 3-month-old girl. Note the symmetrical third-degree orbital hypertelorism, disjoined nares, median cleft lip/palate, and basal encephalocele. (Below, left) Facies D: frontonasal malformation in an 11-month-old girl with third-degree orbital hypertelorism, neurogenic blepharoptosis, alar colobomas with widely separated nasal openings, choanal atresia, and midfacial hypoplasia. She had an interfrontal encephalocele and mental retardation. Facies D is a combination of facies B(major) and facies C. (Below, center) Rugose frontonasal malformation in a 9-month-old girl. Note the thickened corrugated skin, short columella, poorly defined alar-cheek junctions, and symmetrical second-degreeinterorbital hypertelorism. (Below, right) Six-year-old girl with rugose frontonasal malformation and first-degreeinterorbital hypertelorism.
craniofrontonasal dysplasia (Cohen Syndrome, Craniofrontal Dysplasia, Craniofrontonasal Dysostosis, Craniofrontonasal Syndrome)
second most common cause of hypertelorism
all have coronal synostosis, unilateral or bilateral
frontonasal anomalies were (1) short nose, broadened and flat nasal root with a variable degree of tip bifidity (also seen in minor forms of frontonasal malformation), and (2) symmetrical or asymmetrical orbital hypertelorism, usually third-degree severity (in contrast to frontonasal malformation
narrow or high-arched palate
thick, curly, orfrizzy hair that evolved during childhood
narrow/sloping shoulder girdle deformity comprising variably a short, webbed neck, small, prominent, S-shaped or partially absent clavicles, axillary webbing, and prominent, asymmetrical or elevated scapulae (Sprengel deformity)
Asymmetrical orbital hypertelorism associated with paramedian facial cleft(s): Tessier nos. 2-12 and 3-11, either unilateral or bilatera
Frontoethmoidal, Naso-frontal, Naso-ethmoidal, Naso-orbital
Interorbital hypertelorism in patients with nasofrontal encephalocele was symmetrical, but it was asymmetrical in those with asymmetrical naso-orbital encephalocele.