Orbital hypertelorism is an increase in the bone distance between the eye sockets. The pathology is characterized by an incorrect position of the orbits, diplopia, visual impairment. There are multiple cosmetic defects. In the process of diagnosis, the circumference-interorbital index is calculated, visometry, computed tomography, and X-ray examination are performed. Treatment is reduced to performing reconstructive surgical interventions that allow you to restore the correct position of the eye sockets, reduce the distance between them, eliminate a cosmetic defect.
Orbital hypertelorism is not an independent disease, but one of the manifestations of congenital malformations. This dysembriogenetic stigma was first described by the English ophthalmologist L. G. Greig in 1924. According to statistics, about 30,000 children are born annually in the CIS countries with various types of craniofacial pathologies accompanied by orbital hypertelorism. Over the past 35 years, the number of patients with similar dysembriogenesis stigmas has increased by 1.62 times. Pathology is widespread everywhere, it occurs with the same frequency among men and women.
The etiology of the condition is not fully understood. It has been established that all changes in the congenital form of the disorder are laid at the stage of embryonic development, mainly in the first three months of pregnancy. The trigger factors are exposure to ionizing radiation, abuse of alcoholic beverages and psychoactive substances by the mother. The main causes of hypertelorism are:
- Craniosynostosis of cranial sutures. This pathology is characterized by early closure of cranial sutures. Due to the increasing intracranial hypertension, the skull is deformed. An increase in the interorbital distance is observed in brachycephaly and trigonocephaly.
- Craniocerebral hernias. Hypertelorism is one of the typical manifestations of anterior and basal hernial defects of the central nervous system. Anterior hernias are localized in the area of the sagittal suture or at the root of the nose, basal – at the bottom of the anterior or middle cranial pits.
- Crevices of the craniofacial skeleton. With oblique crevices of the face, the arrangement of the orbits is sharply disrupted. The defect is directed from the upper lip filtrum to the lower eyelid. At the same time, other malformations are formed, the most common of which are coloboma of the eyelid, macrostomy.
- Craniofacial malformations. Hypertelorism is often one of the manifestations of rare genetic diseases accompanied by progressive deformities of the skull (Apert syndrome, Crouzon). The distance between the orbits is also sharply expanded in craniofrontonasal dysplasia.
- Craniofacial tumors. The appearance of volumetric formations in the area of the cerebral or facial part of the skull leads to a violation of its shape. When the tumor is localized in the ocular region, the interorbital zone is sharply deformed.
- Traumatic injuries. Craniofacial injuries become the cause of the acquired form of orbital hypertelorism. Similar changes are observed with the displacement of fragments, the formation of bone corns, incorrect implantation of prostheses or metal plates.
In the mechanism of development of hypertelorism, the leading role is assigned to the violation of the formation of the bones of the skull. There are three main stages of morphogenesis: membranous, cartilaginous and bony. The impact of triggers at the membranous stage is associated with the most unfavorable prognosis, the occurrence of the first changes at the stage of bone formation is of less importance. The influence of trigger factors on the fetus in the first trimester of pregnancy can cause the appearance of gross deformities of the skull bones. Such changes are phylogenetically the youngest, difficult to correct surgically.
Visual changes do not always reflect the depth of the lesion. The size of the distance between the eye sockets is significantly influenced by the degree of prolapse and the width of the horizontal plate of the latticed bone. The more the perforated plate protrudes outward, the more pronounced the pathological changes. At the same time, the number of cells of the lattice maze in the anterior sections significantly exceeds the norm. The posterior segment topographically corresponds to the reference values. Clinical symptoms largely depend on the anatomical parameters of the small wings of the sphenoid bone.
There are three degrees of orbital hypertelorism. At 1 degree, the distance between the lacrimal ridges reaches 30-34 mm, at 2 – 35-39 mm, at 3 – 40 mm or more. It is important to remember that the degree of pathology does not in all cases correspond to the existing prolapse. In addition, symmetrical and asymmetric variants of the violation are distinguished. The clinical classification includes:
- True hypertelorism. In the true form, the eye sockets are set far apart from each other due to the excessive width of the median bone formations. In addition to the increased distance between the eyes, an enlarged bridge of the nose and a flattened back of the nose are visualized. The small wings of the sphenoid bone are excessively developed.
- False hypertelorism (epicanthus). With a false variant of the disease, the distance between the inner corners of the orbital slits is increased, but the interorbital distance corresponds to the norm. The bone structures are formed normally, there are no topographic changes.
In most patients, rotation of the eye sockets in the lateral direction is detected. An incomplete cleft of the orbit or an incorrect position of its edges is visualized. A “widow’s peak” may form on the border of the scalp. The shape of the nose is often incorrect – the root of the organ is wide, and the tip is split or has a folded structure. The nasal septum is deformed. Patients complain of visual impairment, double vision, which often becomes a manifestation of concomitant astigmatism or amblyopia. Due to the reduction of the orbit in volume, the development of exophthalmos is possible.
The most common complications are optical neuropathy, exposure keratopathy. These conditions lead to a progressive decrease in visual acuity and the occurrence of amaurosis. With traumatic injuries, compression of the optic nerve with its subsequent atrophy is possible. Similar violations can be traced with the narrowing of the optical channel. In the postoperative period, due to a change in the location of the orbits, provided that binocular vision is preserved, diplopia occurs. Due to excessive convergence of the eyeballs, heterophoria develops. Orbital hypertelorism can also be complicated by chronic conjunctivitis.
To make a diagnosis, it is necessary to calculate the interorbital-circumference index (MOI). The circumference of the head should be divided by the distance between the medial corners of the eye slits and multiply the resulting figure by 100. Orbital hypertelorism is characterized by an index value of 6.8 or more. Measuring the distance between the lacrimal scallops, use a table of age parameters. It is also required to measure the angle of divergence of the sagittal axes of the orbits from the median line. In persons with hypertelorism, this angle varies from 30 to 60 °. During an objective examination, attention is paid to the shape of the eyelids, the location of the external cantal ligaments and the slope of the forehead. Additionally, the following is shown:
- Visometry. There is an asymmetric decrease in visual acuity. In severe cases, high-grade unilateral amblyopia is diagnosed. When performing computer refractometry, it is more often possible to identify a hypermetropic type of clinical refraction.
- X-ray examination. On the X-ray of the facial skeleton in a direct projection, excessive interorbital distance is visualized in combination with the asymmetry of the eye sockets. The study makes it possible to detect gross deformities of the bones of the facial skull.
- Computed tomography. A detailed analysis of axial and frontal sections is carried out. The advantage of the study is the opportunity to study the anatomical features of the structure of the medial walls of the eye socket. CT of the facial skeleton is performed immediately before surgery for detailed planning of the course of the operation.
To eliminate the symptoms of the disease, in most cases, a number of reconstructive surgical interventions are required. The goal of treatment is to achieve a satisfactory cosmetic and functional result. The operation is indicated when the interorbital distance reaches 28 mm or more at birth or exceeds 45 mm by the end of the first year of life. In case of volumetric neoplasms of the craniofacial region, the intervention is carried out regardless of MY indicators. Surgical treatment is preceded by stereolithographic biomodeling. With the help of this technique, a real three-dimensional model is created for planning surgical intervention.
During the operation, a bifrontal craniotomy is performed, then a frontal bando is formed. A part of the bone is resected in the area of the frontal-nasal lattice complex. After circular osteotomy of orbits, bone grafting of orbital zone defects is performed. Excess tissue in the eyelid area is removed by bilateral medial transnasal cantopexy. A bone autograft is formed for the back of the nose and fixed to the frontal bone. The consistent conduct of all stages of the operation creates optimal conditions for the correct transposition of the eyeballs and the optic nerve.
Prognosis and prevention
The prognosis is determined by the degree of severity of orbital hypertelorism. At the initial degrees, the outcome is more often favorable, at the third degree, concomitant damage to the optic nerve and retina can lead to irreversible loss of vision. Specific preventive measures have not been developed. Nonspecific prophylaxis is aimed at preventing the effects of teratogenic factors during pregnancy. To prevent injuries and post-traumatic deformations, it is important to use personal protective equipment (mask, helmet) when working in production conditions. With an increase in the interocular distance in a newborn, it is necessary to be monitored by an ophthalmologist with mandatory measurement of the interocular distance every 3 months.