Cryptophthalmos is a congenital disease characterized by the absence of eyelids, a violation of the development of the eyeball and the cavity of the orbit. Ophthalmopathology is accompanied by a decrease or loss of visual functions, discomfort, pain syndrome, xerophthalmia. To make a diagnosis, an external examination, ultrasound of the eye, visometry, computed tomography of the orbit and biomicroscopy of the eye are performed. In case of partial cryptophthalmos, conservative therapy is recommended (local use of artificial tear analogues, anti-inflammatory and antibacterial agents) and surgical correction of lagophthalmos. In the full form, conjunctival cavity plastic surgery and ectoprosthesis implantation are used.
Cryptophthalmos is classified as an orphan disease. The prevalence of eyelid abnormalities is 0.06% among the total number of malformations. In 2/3 of cases, it is not possible to determine the cause of the pathology, which indicates its sporadic occurrence. 1/3 of patients are diagnosed with a genetic predisposition. As one of the manifestations of Fraser syndrome, this eye development anomaly is diagnosed with a frequency of 0.043 per 10,000 newborns and 1.1 per 10,000 stillbirths. There are no statistical data on the occurrence of an isolated form of cryptophthalmos. Geographical features of the spread of nosology are not noted.
Cryptophthalmos can occur independently or against the background of Fraser syndrome, which is inherited by an autosomal recessive type. Autosomal dominant type of inheritance occurs among patients with an isolated form of pathology. The following causes of the development of the disease are distinguished:
- The impact of teratogenic factors. The relationship between the effect of ionizing radiation, the mother’s intake of medicines, alcoholic beverages and narcotic drugs during pregnancy and the appearance of defects in the child’s visual organ has been established.
- Genetic mutations. Mutations of the FREM2 and FRAS1 genes are associated with the formation of bilateral cryptophthalmos. It is assumed that genetic defects lead to impaired retinoid metabolism. According to another theory, the disease develops due to pathology of epithelial-mesenchymal differentiation.
- Intrauterine infections. The virus of measles, herpes and rubella has a high tropicity in relation to the organ of vision in the case of intrauterine infection of the fetus at 2-7 months of pregnancy.
Normally, eyelid laying occurs at the 8th week of embryonic development. However, differentiation and splitting of the skin fold into the upper and lower eyelid is realized only at 6 months. The final formation of the ocular slit occurs at the 7th month of intrauterine development. Exposure to pathological agents from the 2nd to the 7th month of embryogenesis leads to a violation of the formation of the eyelids and the eye slit. An important role in the occurrence of cryptophthalmos is played by a burdened anamnesis. Confirmation of the hereditary theory of pathogenesis is the diagnosis of a wide range of mutations of the FREM2, FRAS1 genes, including nucleotide substitutions, splicing site mutations, large and small duplications and microdeletions.
The ophthalmology literature describes cases of one- and two-sided damage to the organ of vision. The bilateral variant of pathology is more common in patients with complete cryptophthalmos. From a clinical point of view , the following forms of the disease are distinguished:
- Partial. Develops against the background of Fraser syndrome. The appearance of the patient is characterized by multiple malformations (absence of eyebrows, low location of the hairline on the side surfaces of the forehead, underdevelopment of the wings of the nose). Pathology can be combined with mental retardation of varying degrees of severity.
- Full. Nosology is characterized by the complete absence of eyelids, glands and eyelashes. The conjunctival cavity is not determined. The eyeballs are formed normally.
- Abortive. The absence of eyelids and appendages of the eye is combined with unformed eyeballs.
The clinical picture is determined by the form and nature of the course of the disease. With a partial lesion, patients complain of immobility of the eyelids, severe pain syndrome. Often, after surgery, secondary lagophthalmos develops, accompanied by increased dryness of the eyes, itching and burning. Visual acuity varies depending on the degree of differentiation of the eyeball. With unilateral cryptophthalmos, concomitant anomalies of the development of the other eye are possible. The most common is a coloboma of the eyelid or iris.
With the full version of cryptophthalmos, both eyes are affected. Visual functions are drastically reduced. The complete absence of sebaceous and meibomian glands leads to the development of xerophthalmia. Abortive form is accompanied by irreversible loss of vision and light perception. A low-grade rudiment of the eyeball can cause discomfort or pain. Parents of children with cryptophthalmos note an increased excitability of the child until the moment of surgery. Some patients have problems with social adaptation due to a pronounced cosmetic defect.
Due to the transition of the skin from the forehead to the bulbar conjunctiva and cornea, a common complication of partial cryptophthalmos is opacity and corneal dystrophy. The long course of pathology leads to the formation of multiple ulcerative erosive defects. The presence of an undifferentiated eye rudiment in the orbit often serves as a source of infectious and inflammatory complications. The absence of surgical correction of cryptophthalmos is associated with a high risk of malignant neoplasms (melanoma, retinoblastoma).
The diagnosis of cryptophthalmos includes a physical examination and an ophthalmological examination. Visually, the complete or partial absence of eyelids and eyelashes with the transition of the skin to the cheek area is determined. Detailed diagnosis requires:
- Ultrasound of the eye. The technique allows you to assess the condition of the eyeball, the size of the eye socket, the degree of differentiation of the tarsal plates. The study makes it possible to visualize defects in the structure of the conjunctival cavity.
- Biomicroscopy of the eye. It is used to study the structural features of the conjunctival cavity, cornea and peripheral parts of the eyelids. With a partial variant of cryptophthalmos, the study is carried out using a dye (fluorescein).
- Computed tomography of the orbit. The method is shown in full cryptophthalmia to assess the structure of the walls of the orbit and the anatomical features of the eyeball.
- Visometry. In the case of a full form, vision is absent, with a partial form, it is sharply reduced.
Differential diagnosis of cryptophthalmos is performed with ankyloblepharone and ablefaria. A distinctive feature of ankyloblepharone is the preservation of the mobility of the eyeball against the background of complete or partial fusion of the eyelids. With ablepharia, there is an absence or underdevelopment of the eyelids, which may be accompanied by pathology of the organ of vision. The identification of phenotypic signs of Fraser syndrome requires the consultation of a geneticist.
Treatment tactics are determined by the form of pathology. With a partial type of cryptophthalmos, conservative therapy and prompt elimination of lagophthalmos are indicated. Medical treatment includes the use of:
- Artificial tear preparations. Medicines are used to symptomatically eliminate increased dryness of the eyes, reduce the risk of keratoconjunctivitis and prevent xerophthalmia.
- Anti-inflammatory gels and ointments. Medications of this group are indicated for inflammatory and infectious lesions of the anterior part of the eyes, provoked by the addition of pathogenic flora.
- Antibacterial agents. Instillation of antibacterial agents or the use of ointments are necessary for the development of symptoms of conjunctivitis or keratitis.
Reconstructive intervention involves the transplantation of free flaps of skin and mucous membrane to correct lagophthalmos. With complete cryptophthalmos, total plastic surgery of the conjunctival cavity is shown. To do this, ophthalmologists use 3-4 flaps of the mucous membrane, after which an eye prosthesis is placed in the orbit cavity. Surgical intervention is completed with blepharography. Cosmetic correction is reduced to ocular prosthetics using an ectoprosthesis (epithesis) made taking into account individual anatomical and physiological features of the structure of the organ of vision. The structure of the epithesis includes a prosthetic eyeball, eyelashes, artificial lacrimal and muscular apparatus. The ectoprosthesis is fixed to the eyeglass frame or skin with a special glue.
Prognosis and prevention
The prognosis for an isolated form of the disease is favorable for life, however, it is impossible to restore visual functions. Children in whom cryptophthalmos is one of the symptoms of Fraser syndrome, in most cases die in the first year of life. Specific preventive measures have not been developed. Non-specific prevention is based on the exclusion of alcoholic beverages, narcotic drugs, the effects of ionizing radiation during pregnancy. With a burdened anamnesis, prenatal diagnosis is indicated, which boils down to an ultrasound examination of the fetus in the second trimester of pregnancy. Genetic screening is not carried out.