Coats disease is a congenital pathology characterized by polymorphic changes in retinal vessels in combination with massive intra- and subretinal exudation. Clinical symptoms are represented by leukocoria, decreased visual acuity, the appearance of “fog”, “bright flashes” or specific patterns in front of the eyes. Diagnosis is based on ophthalmoscopy, ultrasound of the eye, OCT, pathomorphological examination, CT of the head, angiography, perimetry, visometry. Therapeutic tactics include the use of laser coagulation, cryotherapy, extrascleral filling. Enucleation is shown at stage IV.
Coats disease (retinal telangiectasia, exudative retinitis) is one of the orphan diseases. The first pathology was diagnosed by V. A. Brayley in 1876. The English scientist G. Coats described the morphological forms of the disease in 1908. The total prevalence of telangiectasia of the inner shell in the structure of ocular pathologies is 1:100,000. According to statistics, exudative retinitis is more common among males. In most cases, the disease is diagnosed when a child reaches the age of seven, however, cases have been described when clinical manifestations debuted at an advanced age. The probability of relapse with adequate treatment is 40%.
The etiology of the disease is not fully understood. The detection of pathology in close relatives suggests the hereditary nature of Coats’ disease. Due to the low prevalence of retinitis, it was not possible to determine the type of the affected gene and the nature of inheritance. Retinal telangiectasia can occur in isolation or against the background of genetic abnormalities: Alport’s disease, Cornelia de Lange syndrome, progressive facial hemiatrophy, craniofacial dysmorphia. The development of pathology is facilitated by the impact of teratogenic factors (ionizing radiation, consumption of alcoholic beverages and narcotic drugs), rubella viruses, herpes zoster, toxoplasma during pregnancy.
In the mechanism of the disease development, the leading role is assigned to the defeat of endotheliocytes of the hemato-retinal barrier. Due to the pathology of the structure of the vascular wall, periodic hemorrhages occur. Cholesterol crystals and lipid-containing macrophages accumulate in the thickness of the retina and the subretinal space. The organization of exudate and (to a greater extent) blood clots initially causes thickening of the shell, and later provokes massive exudative detachment. Genetic mutations leading to the occurrence of pathology have not been established. Scientists are studying the pathogenetic role of the increase in the titer of fibroblast growth factor in the development of retinal telangiectasia.
The classification proposed by G. Coats was based on the nature of vascular changes (without vascular changes, with vascular anomalies, with extensive arteriovenous malformations) and features of exudation. From a clinical point of view , the following stages of the disease are distinguished in Russian ophthalmology :
- I – initial. At stage Ia, vascular malformations and small scattered foci of increased density are detected on the periphery or posterior pole. At stage Ib, malformations and exudates are detected both on the periphery and in the macular zone.
- II – developed. Stage IIa is characterized by increased exudation in the posterior pole, signs of exudative detachment, the size of which is no more than 2 quadrants. At stage IIb, tumor-like deposits, subtotal detachment with a length of 2-3 quadrants are visualized.
- III – far gone. Stage III – a total form of detachment is formed, the formation of subretinal membranes is noted. At stage IIIb, there are objective signs of damage to the uveal tract, clouding of the lens, neovascularization of the iris.
- IV – terminal. Stage IV is characterized by the development of secondary neovascular glaucoma. Stage IVb is characterized by subatrophy of the eyeball (phthisis).
Exudative retinitis is characterized by unilateral damage to the organ of vision. The symptoms of the disease develop during the first 10 years of life. The peak of clinical manifestations occurs in 6-8 years. Rarely, the first signs are detected in the neonatal period. A specific manifestation of the disease is an abnormal reflex of the white retina (leukocoria). The decrease in visual acuity may remain unnoticed for a long time for patients due to the slow progression of pathology. The first symptoms are represented by the appearance of a “fog” or “veil” in front of the eyes. The clinic is most pronounced when a healthy eye is closed.
With a prolonged course of Coats retinitis, there is a violation of the deep and spatial perception of the object. Patients note the appearance of bright flashes of light or rounded opacities in front of their eyes. Visual dysfunction begins with the upper parts of the visual field, which is caused by the accumulation of blood in the lower part. Blood clots, exudate, areas of retinal detachment mechanically interact with the receptor apparatus of the shell. This leads to the appearance of specific “color patterns” that patients may mistake for visual hallucinations. At an early age of the child, parents note that one eye in a photo taken with a flash has a yellow color. Pain syndrome appears with massive hemorrhages, which potentiate an increase in intraocular pressure.
Abnormal growth of blood vessels in the posterior parts of the inner shell of the eyeball is a common cause of secondary glaucoma and lens opacity. The defeat of the retina causes its thinning, detachment, the formation of multiple ruptures. Due to pathological changes in blood vessels, subretinal hemorrhages, hyphema and hemophthalmos often occur. Frequent coagulation in Coats disease provokes the formation of macular traction and folds. Excess of laser exposure power underlies the development of macular gliosis. The high risk of postoperative bleeding is due to necrotic changes in the vascular wall.
For a detailed examination of the patient, physical and special diagnostic methods are used. Visual examination reveals diffuse hyperemia of the conjunctiva, clouding and smoothness of the iris pattern. The complex of ophthalmological examination includes:
- Ophthalmoscopy. Convoluted and dilated vessels of the inner shell are determined, most pronounced in the peripheral parts. Areas of hemorrhage, areas of detachment of the inner shell are visible. The swelling of the ZEN is characteristic, signs of its partial atrophy are less often observed.
- Perimetry. The study is carried out periodically to monitor changes in the visual field. The expansion of the affected area leads to an asymmetric narrowing of the field of vision, the appearance of cattle, which indicates a progressive course of pathology.
- Visometry. Allows you to diagnose the degree of visual dysfunction. The result of the test with mydriatics is negative.
- Retinal angiography. With the additional use of fluorescein dye, vascular malformations, zones of occlusion of the links of the microcirculatory bed, newly formed arteriovenous shunts are visualized. Fluorescence angiography is performed on the eve of surgery to determine the areas to be coagulated.
- Optical coherence tomography. The technique makes it possible to identify the thickening of the retina, the exudate layer behind the inner shell, to measure the parameters of the optic nerve disc.
- Ultrasound of the eyes. Ultrasound examination shows hyperechoic accumulations behind the vitreous body. The posterior acoustic shadow is absent or weakly expressed. Signs of hemophthalmos and subretinal hemorrhages are determined. The study is prescribed for the purpose of differentiation with malignant neoplasms.
- CT of the head. When performing computed tomography in the axial projection behind the vitreous body, a seal formed by an accumulation of exudate of a protein nature is revealed.
- Pathomorphological research. Macroscopic diagnosis reveals retinal detachment, the presence of exudate. Microscopically, the thickening of the vascular wall is visible, which alternates with thinning. The lumen of the vessels is expanded unevenly. The composition of the exudate includes cholesterol crystals, macrophages, pigmentocytes, erythrocytes, hemosiderin.
Differential diagnosis is carried out with retinoblastoma, malignant medulloepithelioma, Ilsa disease. Instrumental methods do not allow to detect visible differences between retinitis and oncopathologies such as retinoblastoma and medulloepithelioma. The presence of a malignant neoplasm is indicated by an increase in the level of neuron-specific enolase in the blood and lactate dehydrogenase in the fluid of the anterior chamber. Unlike retinal telangiectasia, preretinal fibrosis and recurrent vitreous hemorrhages are detected in Ilsa disease, there are no solid exudates.
Treatment tactics are determined by the clinical stage, the age of the patient at the time of the manifestation of the disease. The effectiveness of therapy is highest with its early application. The main methods of treatment include:
- Laser coagulation of the retina. It is indicated at the Ia-IIa stages of the disease, provided that the affected area does not exceed 240 °. Treatment is carried out in courses. The average number of courses is 2-6 with intervals of 3-4 months. Initially, a barrier coagulation is prescribed around the malformation zones. Next, the detachment zone is coagulated, while applying 2-3 layers of coagulates. If additional vascular anomalies are visualized after 5-7 days, another session of the procedure is shown.
- Retinal cryopexy. It is used in addition to laser coagulation for localization of defects on the periphery of the inner shell at grade Ia-IIa. In the diagnosis of IIb-IIIa degree, the technique is used in isolation.
- Extrascleral filling. The expediency of prescribing the technique in the development of diffuse exudative retinal detachment at the IIb-IIIa stage is proved.
- Conservative therapy. The use of drugs from the group of angioprotectors, antiplatelet agents is shown.
While maintaining visual acuity, pleoptic treatment of the affected eye is carried out using laser stimulation, color pulse therapy, reflexology. The complicated course of pathology often requires vitrectomy, excision of subretinal membranes. The exudate must be drained by transretinal access. Tamponade is carried out using a special silicone oil or perfluorocarbon. In parallel, endodiathermy, coagulation of bleeding vessels is performed. Enucleation is used only at the terminal stage of Coats’ disease in the case of complete blindness.
Prognosis and prevention
The prognosis for Coats’ disease largely depends on the patient’s management tactics. Early laser coagulation of the retina in 88% of cases allows to preserve visual functions, and in 70% – to achieve their complete stabilization. With passive observation of the patient, blindness develops in 94% of cases. Prevention of deep visual deprivation is reduced to the appointment of a dosed occlusion of a better-seeing eye. Patients with an established diagnosis of retinitis pigmentosa need to be examined by an ophthalmologist once every six months. Regular application of coagulates in the area of pathologically altered vessels allows to achieve remission.