Microphthalmia is a reduction in the size of the eyeball, in which its longitudinal axis does not exceed 21 mm in an adult and 19 mm in a child. The disease is manifested by a decrease in visual acuity, facial asymmetry, increased tearfulness, discomfort, with the formation of cysts in the orbital cavity – pain syndrome. Diagnostics includes ultrasound of the eye, visometry, refractometry, CT of the orbit, biomicroscopy of the eye. Treatment tactics are reduced to a posterior sclera bandage, cosmetic prosthetics with or without pre-implantation of a skin-fat graft. Conservative therapy is based on daily instillations of antiseptics.
Microphthalmia is one of the congenital pathologies of the organ of vision. The prevalence of the disease varies from 1 to 2.1 cases per 10,000 population. Among the total number of visual organ lesions is 0.4%. According to the statistics available in ophthalmology, congenital microphthalmia occupies from 3.2 to 11.2% in the structure of childhood blindness. It was found that in 3/4 of cases, the development of an anomaly of the visual organ is provoked by the pathological course of pregnancy, less often childbirth. Only in 1/4 the disease is a manifestation of a genetic syndrome. Nosology occurs with the same frequency among men and women. Geographical features of the spread of microphthalmia are not noted.
Microphthalmia can develop in isolation or be one of the manifestations of genetic pathology. Ophthalmologists often fail to establish the etiology of the disease. May provoke the occurrence of:
- A group of TORCH infections. There is a high probability of damage to the organ of vision during intrauterine infection with toxoplasmosis, rubella, herpes virus. Penetrating through the hematoplacental barrier, pathological agents enter the fetal bloodstream, causing multiple defects.
- Teratogenic effect. The risk of microphthalmia increases under the influence of such teratogenic factors as ionizing radiation, smoking, alcohol consumption, narcotic substances, medicines.
- Amniotic constriction syndrome. The strings of Simonara have the form of dense threads that form in the fetal bladder and squeeze the fetus. The formation of amniotic constrictions at different stages of pregnancy leads to the fact that the eyeball does not form at all or significantly decreases in size.
- Genetic syndromes. Genetic mutations are the cause of the Temple Al–Ghazali, Delleman, Peters, Rieger syndromes, which are manifested by multiple anomalies, including microphthalmia.
The leading role in the development of microphthalmia is assigned to the action of teratogenic factors. The degree of severity of hypoplasia of the eye correlates with the time of exposure to pathological agents. The earlier the teratogenic or embryotoxic effect occurs, the lower the level of differentiation of the eyeball. It is proved that the occurrence of this malformation is associated with point mutations of the STRA6, PAX6, SOX2, OTX2 and VSX2 genes. Chromosomal mutations cause the secondary development of an eye anomaly as one of the multiple manifestations of the genetic syndrome. The appearance of the “colobomatous” form in most cases is due to amniotic accretions.
Usually there is a unilateral lesion of the organ of vision, less often – bilateral. Microphthalmia is a common manifestation of a number of genetic diseases. The isolated form is classified into:
- Idiopathic. The diagnosis of “idiopathic microphthalmia” indicates that it was not possible to establish the etiology. Also, sporadic development excludes the action of pathogens during the entire intrauterine period.
- Hereditary. Depending on the type of inheritance, this variant of pathology is divided into autosomal dominant, autosomal recessive and X-linked. A wide range of inheritance types leads to a high prevalence of the disease.
Clinical manifestations of microphthalmia are largely determined by the degree of development of the eyeball, the presence of concomitant diseases and complications. Pathology is often accompanied by irreversible loss of visual functions. In rare cases, visual acuity is normal or slightly reduced. Patients complain of increased tearfulness, a feeling of a foreign body. Microphthalmia is combined with the pathology of the development of the eyelids (coloboma, entropion, lagophthalmos). Irritation of the conjunctiva with eyelashes leads to pronounced discomfort and soreness. With a significant decrease in the eyeball, deformities of the bones of the facial skull are observed – lowering of the eyebrow, lifting of the wing of the nose and the corner of the mouth on the side of the lesion. Facial asymmetry worsens with the growth of the child in the absence of timely treatment. In some cases, the social adaptation of patients in children’s groups is disrupted.
Microphthalmia is complicated by the formation of multiple cysts in the orbital cavity. An increase in cystic formations in volume leads to compression of surrounding structures and severe pain syndrome. The eyeball may have a “colobomatous” appearance. Common complications of pathology are keratitis, conjunctivitis of infectious origin. In severe cases, the addition of pathogenic flora leads to pan- and endophthalmitis. It is statistically proven that patients with microphthalmia are more at risk of developing malignant neoplasms of intraorbital localization.
To make a diagnosis, an external examination, a special ophthalmological examination is carried out. Due to the fact that microphthalmia is often a symptom of genetic pathology, genetic DNA analysis is additionally indicated, the material for which is blood or buccal epithelium. Ophthalmological examination includes:
- Biomicroscopy of the eyes. It is carried out in order to identify pathological changes in the anterior part of the eyes, opacity of optical media, assessment of the state of the palpebral and orbital conjunctiva.
- Visometry. The technique is used to determine visual acuity.
- Refractometry. The study allows us to study the optical properties of the eye and diagnose refractive errors (myopia, hypermetropia, astigmatism).
- Ultrasound of the eyes. The method is used to examine the eyeball, determine the echogenicity of its structures, and identify multiple cysts.
- CT of the orbit. It is performed before the proposed surgical intervention to assess the anatomical and physiological features of the structure of the bone walls, the distribution of periorbital fiber.
Patients with microphthalmia are advised to consult a geneticist. Prenatal screening of the disease is currently available. Differential diagnosis is carried out with anophthalmos, nanophthalmos, cryptophthalmos. A distinctive feature of cryptophthalmos is the absence of an eye slit, eyelashes and glands. With anophthalmos, the eyeball is not visualized in the orbital cavity or its low-differentiated rudiment is located. Nanophthalmos is characterized by thickening of the scleral capsule, pronounced hypermetropia and a high risk of developing angle-closure glaucoma.
Therapeutic tactics in microphthalmia is determined by the degree of hypoplasia of the eyeball and the duration of the disease. The treatment is based on surgical correction. Conservative therapy is used only for the prevention of secondary complications and is based on the installation of antiseptic solutions. Surgical treatment includes:
- The posterior bandage of the sclera. The operation is indicated for minor hypoplasia of the eye (reduction of the anteroposterior axis by no more than 3 mm). During the intervention, allograft strips are carried out under the rectus muscles, followed by attachment to the episclere. If necessary, a repeat operation is possible.
- Cosmetic eye replacement. It is used for severe hypoplasia (5 mm or more). The use of a thin-walled prosthesis allows you to maintain the mobility of the eyeball. With hypersensitivity of the cornea, its deepithelization is indicated. A rounded allograft is placed on the surface of the cornea.
- Implantation technique. This method is used if the anterior-posterior vector does not exceed 10 mm. During the operation, the skin-fat graft is placed in the retrobulbar space and delayed prosthetics is performed.
Prognosis and prevention
The prognosis for this developmental anomaly is favorable for life and work capacity. If microphthalmia occurs against the background of genetic pathology, then the prognosis depends on the characteristics of the course of the underlying disease. Early treatment makes it possible to avoid a number of complications, prevent a decrease in visual functions and a violation of facial symmetry. There are no specific preventive measures. Non-specific prevention includes prevention of teratogenic factors, timely diagnosis and treatment of TORCH infections. With a burdened hereditary history, genetic screening is recommended.