Overview

Telecanthus (‘tele’ meaning far, ‘canthus’ meaning corner of eyelids) is a disorder characterised by an increased distance between medial canthi (inner corners of the eye lids) with normal interpupillary distance, but when accompanied by irregular interpupillary distance it is considered hypertelorism, which is where the entire eye orbits (eye sockets) are set further apart, not just the skin between them. Telecanthus is associated with many congenital disorders, such as Down syndrome, Ehlers-Danlos syndrome, Waardenburg syndrome, etc.^1, and the accurate evaluation of telecanthus can influence the diagnosis of these conditions. Telecanthus can also be due to facial trauma and craniofacial syndromes, such as sinus and orbital tumours caused by Kartagener syndrome.² The precise measurement of telecanthus can influence surgical and treatment planning of these conditions. The evaluation of telecanthus is also useful in planning cosmetic procedures of the eyes.

How is telecanthus clinically assessed?

Telecanthus can be initially evaluated using physical examination, using callipers or other digital tools such as cameras, to gain three pieces of information:

• Intercanthal distance: distance between medial canthi or inner corners of eyelids
• Interpupillary distance: distance between pupils
• Outer canthal distance: distance between the outer corners of the eyelids

These values are compared to age-matched and sex-matched normative local data, as there is also significant ethnic variation in canthal distances.³

In some cases, this information may be enough for diagnosis, but in some cases, it may be in the grey areas, or more precise information is required for surgeons to plan procedures. This may be due to facial swelling, or people who are unable to stay still, making precise measurement difficult. In these situations, imaging would be utilised for more precise information, as millimetre differences can change the surgical approaches which are viable.

In some patient populations, a physical exam may not be possible due to patient cooperation, which may not be possible with children or trauma patients, and soft tissue variation, particularly the eyelids. 

How is imaging used for telecanthus evaluation?

Imaging is performed using technologies like the CT scanner, MRI machine, and X-rays to take pictures of the internal anatomy and gain more precise measurements of anatomical differences.

Why is Imaging useful for telecanthus?

• It can act as confirmatory information for a diagnosis made from physical examination
• Allows more precise measurement of facial dimensions, including both soft tissue and bones, which can be stored and referred to later
• It shows hidden injuries, which can’t be physically examined
• It is essential for surgical planning, especially for reconstructive surgeries
• It can be used to monitor changes before and after surgeries and to monitor outcomes after surgeries

The physical examination can be analogised to a SatNav with satellite view: a regular map (physical exam) gives you a general idea, but a satellite (CT or MRI) lets you see the terrain, buildings, etc, all the small details that matter.

What types of imaging modalities are used for telecanthus evaluation?

Imaging modalities vary in detail, purpose and radiation exposure. Below is an explanation of the main imaging modalities used for telecanthus evaluation [3,4,5]:

Key measurement from imaging for telecanthus:

When doctors interpret imaging, they’re measuring key distances to gain information on the patient's anatomy, such as:

• Interpupillary, intercanthal and outer canthal distances, which were explained above.
• Nasal bridge width - width of the base of the nose
• Medial orbital wall length - length of the inner eye socket wall
• Angular orientation of medial canthal tendon - to measure attachment of tendon, or disturbance

These values can be compared to sample data to identify what areas of the patient’s anatomy are abnormal.

Clinical scenarios where imaging is useful:

In many situations, the more precise/reliable measurements from imaging are necessary for diagnoses and management of conditions^2,5,6:

Limitations of imaging:

Imaging isn't the optimal solution to every problem; the key limitations are:

• Radiation exposure(X-ray and CT) has to be risk-managed, especially for pediatric patients
• Cost and Access: need access to MRI and stereophotogrammetry infrastructure, both the machine and technicians/operators need to be available
• Image interpretation skill: Some patients may have subtle conditions, which need trained subspecialist doctors to interpret

Which is why both physical examination and imaging interpretation skills are valuable.

FAQs:

What is the difference between an X-ray and a CT scan?

X-ray is a stationary 1-dimensional scan; the CT scanner takes multiple images while rotating, allowing it to form a detailed 3d image.

Can telecanthus correct itself as a child grows?

If diagnosed with true telecanthus due to bone structure abnormalities or congenital disorders, it is unlikely to resolve with no intervention. However, if it's due to other conditions, it may resolve over time, in mild cases of telecanthus.

Is surgery always needed for telecanthus?

Not always, it depends on severity, cause, symptoms, and patient choice. If you have mild symptoms, another approach may be used instead of surgery.

Is imaging radiation safe for children?

Generally, precautions are taken to reduce radiation exposure from CT scans, and alternative low-dose imaging protocols are used for children.

Does telecanthus affect vision?

Telecanthus by itself is not indicative of affected vision, but certain syndromes and trauma which cause telecanthus can reduce eye function.

Summary:

Telecanthus may seem like a small detail in a person’s appearance, but it can be a clue to more complex structural or congenital conditions. Proper evaluation involves precise measurements, clinical skill for physical examination, and most importantly, imaging modalities that let us look beneath the surface.

CT scans provide a detailed view of the facial bones, MRI helps assess soft tissue, and 3D surface scanning allows non-invasive tracking of facial symmetry and growth. Each modality plays a complementary role, much like different instruments in an ensemble — all working together to provide a diagnosis and treatment plan.

By combining these methods with good clinical judgment, clinicians can ensure that patients with telecanthus receive the right care, whether for function, appearance, or both.