Telecanthus is observed when there is an abnormal insertion or length of the medial canthal tendons and can be congenital or acquired. It can be an isolated finding, but it also occurs in the context of many syndromes, most commonly blepharophimosis syndrome and Waardenburg syndrome type 1. According to the Online Mendelian Inheritance In Man (OMIM) website, 156 additional syndromes may be associated with telecanthus,⁷ including the telecanthus-hypospadias syndrome, Down syndrome, fetal alcohol syndrome, Cri du Chat syndrome, Klinefelter syndrome, Turner syndrome, frontonasal dysplasia with alar clefts, Opitz GBBB syndrome, nasopalpebral lipoma-coloboma syndrome, or Jacobsen syndrome.⁷

Primary telecanthus is defined as an increased distance between the inner canthi with a normal outer canthal distance and a normal interpupillary distance; secondary telecanthus, on the other hand, is characterized by an increase in all three parameters and is associated with ocular hypertelorism.³,⁶ Hypertelorism (teleorbitism, or ocular hypertelorism) is a clinical-radiological term that is used in the literature to describe widely spaced orbits.⁸,⁹

The medial canthal tendon may also detach or rupture following trauma to the mid-face.¹⁰ This usually occurs owing to disruption of the bony attachment of the medial tendon following naso-orbito-ethmoidal (NOE) fractures types II and III.¹⁰,¹¹,¹² Disruption of the anterior limb of the medial canthal tendon alone does not produce telecanthus. For telecanthus to occur, this requires disruption of both the anterior and posterior limbs of the tendon.¹⁰,¹³ A less frequent cause of traumatic telecanthus is a degloving injury where the skin with the underlying tissue is completely torn off in the medial canthal region. The subsequent shearing forces result in avulsion of the medial canthus. By definition, degloving injuries do not involve trauma to the bone.¹⁰,¹⁴

The normal intercanthal distance usually is less than 20 mm in infants and less than 24 mm in older children, whereas in adults the normal range for intercanthal distance is 25 to 37 mm in women and 26 to 38 mm in men.¹³,¹⁵ In the absence of strabismus, these values are typically half the interpupillary distance, and values that exceed this parameter are indicative of telecanthus.¹⁵

In patients with congenital telecanthus, the principal presenting symptom is cosmetic, and despite the unusually long medial canthal tendons, patients rarely complain of tearing. Clinically, the interpupillary distance is normal, but the intercanthal distance is wide (Figure 41.1). As a result, the eyes may appear somewhat esotropic since the amount of visible medial sclera is less than the lateral scleral width (Figure 41.2).

In syndromic cases, there may be associated findings such as blepharophimosis, ptosis, and epicanthus inversus in patients with blepharophimosis syndrome (Figure 41.1),¹⁶ or severe hearing impairment, localized hair albinism (a white forelock of hair or early graying), bright hypochromic blue irides, or iris heterochromia in cases of Waardenburg syndrome type I.¹⁷