Polycoria is an ophthalmopathology in which two or more pupils are located in the iris. Clinical manifestations include visual discomfort, decreased visual acuity, the appearance of “fog” in front of the eyes, photophobia. A physical examination is sufficient to make a diagnosis. In order to clarify the form of the disease, a test with mydriatics, ultrasound of the eye, visometry, perimetry, biomicroscopy of the eyes is carried out, the reaction of the pupils to light is studied. The use of operational tactics (iridoplasty) is recommended. If there are contraindications to surgical treatment, contact lenses are used to eliminate a cosmetic defect and correct visual dysfunction.
Polycoria is a congenital malformation of the iris, which is detected in the first year of a child’s life. Isolated cases of acquired pathology in mature persons are described. There are no statistics on the overall prevalence of the disease. As one of the manifestations of Axenfeld-Rieger syndrome, perforated iris defects are diagnosed with a frequency of 1:200,000. There are about 35,000 people with this nosology in the world. Polycoria occurs with the same frequency among males and females. Geographical features of the spread of the disease are not observed.
The etiology of the disease is not fully understood. The genetic theory of the occurrence of pathology is based on the detection of a mutation of the PAX6 gene. The main causes of polycoria:
- The effect of teratogenic factors. Anomalies of the iris are often associated with exposure to ionizing radiation, the use of alcohol and drugs by the mother during pregnancy.
- Coloboma of the iris. The formation of additional holes provokes partial closure of the coloboma by meso- or ectoderm tissue at the stage of embryonic development.
- Intrauterine infections. The defeat of the iris causes infection with the rubella virus and herpes zoster or toxoplasma, which have the ability to disrupt the differentiation of intraocular structures and cause multiple fetal malformations.
- Iridocorneal endothelial syndrome. This pathology is based on essential mesodermal dystrophy or partial atrophy of the shell. In those areas where pronounced thinning of the shell is replaced by atrophic changes, false polycoria is formed.
- Iatrogenic effects. Pseudopolycoria occurs a second time in the postoperative period in patients who have undergone surgery on the iris, due to the excess power of laser radiation during iridoplasty.
- Traumatic injury. The formation of several pupils is often caused by injuries or burns of the organ of vision. At the same time, a false form of the disease is observed.
- Axenfeld-Rieger syndrome. The development of polycoria in this nosology is associated with congenital hypoplasia of the iris and ectopia of the pupil.
True polycoria occurs due to a violation of the embryonic development of the eyeglass. The outer pigment layer is a structure of neuroectodermal origin, from which the epithelial layer of the iris, the sphincter and dilator of the pupil are normally formed. Stromal tissue develops from the anterior segment of mesenchymal tissue. Under the action of teratogenic factors or infectious agents at 4-6 weeks of fetal development, the process of differentiation of the two-layer visual glass and the formation of retinal pigment epithelium is disrupted. Because of this, at the birth of a child, multiple perforated defects are observed in the iris area.
False polycoria develops if the pupillary membrane does not respond to timely reduction. The formation of pseudopolycoria is often based on the phenomenon of mesodermal dysgenesis or neurotrophic disorders, which leads to the formation of anomalies in the structure of the iris. The role of lens adhesion to the cornea at the stage of separation of ecto- and mesoderm leaves in the occurrence of this pathology is proved. Due to the fact that several holes are formed in the shell, the sphincter of the pupil cannot fully function. This leads to a spasm of accommodation and visual dysfunction. The influence of a genetic mutation on the development of polycoria in compromised individuals is being studied.
Polycoria is one of the congenital malformations. However, it has been proven that an acquired variant is possible in patients with a history of iris pathology. The disease can symmetrically affect both eyes or have a unilateral course. From a clinical point of view , the following forms of polycoria are distinguished in ophthalmology:
- True. It is characterized by the presence of more than one pupil, provided that the reaction to light is preserved.
- False (pseudopolycoria). In this variant of the disease, the pupil has the shape of an hourglass, because the rudiments of the membrane formed in the embryonic period connect the edges of the pupil, which are located parallel to each other.
Patients with polycoria note pronounced discomfort in the eye socket area when performing visual work. At an early age, asthenopic complaints arise caused by the formation of perforated defects of the iris. Getting a lot of light on the retina leads to photophobia. There may be difficulties when working at the computer due to the bright glow of the monitor, when watching TV. Visual acuity decreases only on the side of the lesion. Frequent symptoms are blurred vision, diplopia. Parents note that the child often closes his eyes, trying to limit his participation in vision. The appearance of visual field defects in the form of cattle and photopsies is associated with the general aura of migraine. A cosmetic defect often leads to difficulties in social adaptation.
A common complication of polycoria is amblyopia, the occurrence of which is caused by a violation of the accommodative ability of the eyeball. If the pupil size is less than 1.5 mm, visual functions cannot be restored by using contact lenses. Patients are at risk of developing infectious and inflammatory reactions (keratitis, conjunctivitis, pan- and endophthalmitis). In rare cases, polycoria is complicated by ocular migraine, secondary open-angle glaucoma. Degenerative-dystrophic and erosive changes of the iris are more often detected in patients, which is due to the peculiarities of the structure and the use of contact lenses.
To verify the diagnosis, it is enough for an ophthalmologist to conduct an external examination. In most cases, 2-3 pupils are visualized, one of which is larger in size. The holes in the iris are rounded, rarely irregular in shape. Special ophthalmological examination includes:
- The study of pupillary reaction. With true polycoria, the reaction of the pupils to bright light is preserved, sluggish. The size of the holes in the iris is reduced (less than 2.5 mm), the position is eccentric, the contour is uneven. Convergence and accommodation are disrupted. With a false form, the reaction of the pupils does not occur.
- Ultrasound of the eyes. Ultrasound examination makes it possible to visualize the pupillary sphincter in the true variant and its absence in the area of additional holes in pseudopolycoria. The technique is also used to identify concomitant clinical manifestations in the development of polycoria against the background of Axenfeld-Rieger pathology.
- A sample with mydriatics. Instillation of M-holinoblockers causes persistent dilation of the pupils in the true form. The use of a sample with a false variant does not potentiate mydriasis.
- Biomicroscopy of the eye. It allows you to detect degenerative-dystrophic changes in the iris, study in detail the characteristics of the pupillary openings, diagnose signs of inflammatory and infectious diseases of the anterior part of the eyeball.
- Perimetry. When additional pupils are localized on the periphery of the iris, a narrowing of the visual field is diagnosed.
- Tonometry. Measurement of intraocular pressure is carried out to identify signs of increased ophthalmotonus, differential diagnosis between ocular migraine and true ophthalmohypertension.
- Visometry. The study allows us to assess the degree of visual acuity reduction. Additionally, refractometry can be performed to study the type of clinical refraction in the patient.
Management tactics are determined by the severity of symptoms, the size and number of pupils, and the age of the patient. Early elimination of the defect makes it possible to prevent the development of accommodation spasm and amblyopia. In the treatment of polycoria , it is used:
- Iris plastic surgery. Surgical intervention is performed in a closed manner after preliminary paracentesis. With extensive damage to the iris or multiple defects of the organ of vision, implantation of an iridocrustal diaphragm is indicated at one of the stages of the operation.
- Surgical correction. If pathology is detected during the newborn period and the pupil diameter is more than 2 mm, stitches are applied with the formation of a single pupillary opening. This technique is applicable if the child has at least three pupils in one eye.
- Symptomatic therapy. It is used only if there are absolute contraindications to surgical treatment. It comes down to the use of cosmetic lenses to eliminate a visual defect. Correction of visual acuity is carried out using contact lenses or glasses.
Prognosis and prevention
The prognosis for life and work capacity in polycoria is favorable. With timely elimination of the malformation, complete restoration of visual functions is possible. Specific prevention of the disease has not been developed. Non-specific preventive measures are reduced to excluding the effects of teratogenic factors and preventing intrauterine infection of the fetus with pathogenic agents capable of penetrating the hematoplacental barrier. To prevent the occurrence of the acquired form, it is recommended to use personal protective equipment (glasses, helmet) in working conditions at work.