Hypotelorism - An Overview

Introduction

Hypotelorism is an abnormality of the eyes or orbit in which the distance between the two eye sockets or orbits decreases. In ocular hypotelorism, the distance between the eyes or pupils decreases, whereas, in orbital hypotelorism, the length of the orbital walls decreases.

In fetal hypotelorism, the association of midline craniofacial defects is also seen. However, hypotelorism is primarily associated with other anomalies, like holoprosencephaly, trigonocephaly, and microcephaly.

What Is the Normal Interocular Distance?

The usual range of interorbital distance is measured in anteroposterior facial radiographs. Values range from 15 millimeters in infants to 23 millimeters at 12 years. In girls, the interorbital space is narrower as compared with boys. The interorbital area remains the same until the age of 18 months. After that, interorbital growth in females closes at 13 years, but in males, it continues until 21.

What Is the Incidence of Hypotelorism?

The occurrence of hypotelorism is uncommon. It is seen in one in 20,000 live births. Hypotelorism is seen in one in 1220 deliveries in Taiwan. Ethnic background plays a vital role in the interorbital distance. For example, individuals with ancestry from Mongolians considered hypotelorism as a normal genetic variation.

What Are the Causes of Hypotelorism?

It is a developmental defect, mainly due to insufficient development of the brain hemisphere. It may also occur due to the early closure of Metopic sutures (sutures that separate two frontal lobes).

It is also seen in association with certain conditions, including:

• Trisomy 13 is also called Patau syndrome (a rare severe genetic disorder in which there is an additional copy of chromosome no 13 in some or all of the body cells).

• Fragile X syndrome (a genetic condition that causes developmental problems, including learning disabilities and memory loss in patients).

• Prader-Willi syndrome (a rare genetic disorder with physical, mental, and behavioral problems and is seen around two years of age).

• Fetal alcohol syndrome occurs mainly due to excessive alcohol consumption during pregnancy, mainly during the first month (which causes physical and behavioral problems).

• Meckel -Gruber syndrome (an autosomal recessive condition that affects the liver and kidneys and causes enlarged kidneys and nervous malformations).

What Is the Clinical Presentation for Hypertelorism?

There are specific abnormal findings associated with hypotelorism that include:

• The most common neurologic sign seen in patients is developmental delay.

• Sometimes, there is nasal and premaxillary agenesis (complete absence of organs or lack of cells).

• In addition, there is poor vision associated with these patients.

• Often patients are related to mental retardation.

• In some cases, associated midline cleft lip or palate is also seen.

• Endocrine disorders such as diabetes insipidus (imbalance of fluids in the body) or growth hormone deficiency are also associated with some patients.

How to Diagnose Orbital Hypotelorism?

• The prevalence of Isolated hypotelorism is scarce. However, A proper anatomic scan and karyotype analysis help detect malformations or any chromosomal abnormalities if present.

• The imaging modality is used to diagnose the condition.

• First, an ultrasound diagnosis on the axial view is made, and then an interocular distance is measured.

• Routine orbital biometry (ocular measurements) is not done, but these measurements are necessary whenever an orbital anomaly is suspected.

• Measurements include ocular diameter, interocular distance, and binocular distance. In addition, a lateral view helps assess the orbit's intraocular soft tissues, lenses, and posterior walls.

• Values of normal ocular measurements are available for early, mid, and late gestation.

• In suspicious cases, measurement calculation and comparison with standard values may be helpful.

What Is the Sonographic Finding in Hypotelorism?

Hypotelorism is more obvious sonographically or radiographically rather than clinically. Therefore, imaging the orbit and measuring interorbital distance is not a routine diagnostic procedure in most centers during fetal life. However, if pregnant women have already been affected, the child should take fetal orbital measurements. When orbital hypotelorism is suspicious in fetal life, it should be considered severe because hypertelorism is strongly associated with any cerebral abnormality.

What Is the Treatment for Hypotelorism?

The treatment of hypotelorism depends on the severity of the condition and whether it occurs in isolation or as part of a broader syndrome. The primary goals of treatment are to address functional issues related to eye alignment and improve the overall appearance of the affected individual's face. Treatment options may vary and can include:

1. Observation and Monitoring: Treatment may not be necessary in mild cases of hypotelorism, where there are no significant functional problems or associated syndromes. Regular observation and monitoring by medical specialists, including pediatricians, ophthalmologists, and craniofacial surgeons, are essential to track any changes in the condition over time.

2. Glasses and Contact Lenses: Sometimes, wearing glasses or contact lenses may help individuals with hypotelorism improve their vision and eye alignment. Specialized lenses can be prescribed to optimize visual acuity and minimize any associated refractive errors.

3. Reconstructive Craniofacial Surgery: For more severe cases of hypotelorism or when it is associated with other craniofacial abnormalities, reconstructive craniofacial surgery may be considered. This surgical intervention aims to correct the alignment of the eyes and facial structures, improving appearance and function. The surgical procedures may vary depending on the individual's unique condition and needs. Some common surgical techniques used in the treatment of hypotelorism include:

• Orbital and Periocular Surgery: This involves adjusting the position of the eyes and their surrounding structures to achieve better alignment and symmetry. Surgeons may work on the bony structures around the eyes and reposition the soft tissues to optimize results.

• Midface Advancement: In some cases, the midface may be recessed, contributing to the appearance of hypotelorism. Surgical advancement of the midface can help improve the positioning of the eyes and other facial features.

• Cranial Vault Reconstruction: In individuals with hypotelorism associated with craniosynostosis (premature fusion of the skull bones), cranial vault reconstruction may be necessary for proper skull growth and development.

• Nasal Reconstruction: If the nose is affected by hypotelorism or other abnormalities, surgical interventions may improve its shape and function.

4. Supportive Therapies: Depending on the individual's needs and any associated conditions, supportive therapies may be beneficial. These can include:

• Speech Therapy: If hypotelorism affects the positioning of the oral structures, speech therapy can help address speech or swallowing difficulties.

• Developmental Support: Children with hypotelorism may benefit from early intervention and developmental support to optimize their growth and development.

• Psychological Support and Counseling: Living with a craniofacial anomaly can have significant psychosocial implications for affected individuals and their families. Psychological support and counseling are essential components of the management of craniofacial conditions. Professionals experienced in working with craniofacial patients can offer guidance, coping strategies, and support to help individuals build self-esteem and develop a positive self-image.

What Is the Prognosis for Hypotelorism?

The prognosis is poor for hypotelorism. Mortality is high for hypotelorism. The associated syndromes are lethal and can lead to death. Mental retardation is inevitable in cases associated with holoprosencephaly meaning severe skull and facial defects. Survival becomes difficult for the patient. The prognosis of the condition mainly depends on the underlying syndrome or the cause.

Conclusion

Hypotelorism is a defect mainly affecting orbits. Orbital distance decreases in hypotelorism. It is a rare developmental anomaly. Isolated hypotelorism is rare but can be seen with specific syndromes and is associated with chromosomal abnormalities. Therefore, fetal diagnosis is essential in suspicious cases.