bubble_chart Overview

This disease was first reported by George Coats in 1908, hence it is also known as Coats disease. It is mostly seen in male adolescents, less frequently in females, and rarely occurs in adults. It usually affects one eye, occasionally both. The disease progresses slowly and is progressive. It is difficult to detect in the early stages and is often only noticed when there is a significant decrease in vision, the appearance of leukocoria, or the development of exotropia due to disuse.

bubble_chart Etiology

This disease is a retinal vascular abnormality characterized by the loss of the endothelial cell barrier function, leading to massive plasma leakage beneath the neurosensory layer of the retina, resulting in widespread retinal detachment. However, whether this retinal vascular abnormality is congenital or acquired, primary or secondary, remains undetermined to date.

bubble_chart Pathological Changes

In the literature, most histological examinations of this disease are of advanced stage cases. Trpathi and Ashton (1971) conducted electron microscopic examination on a tissue specimen from an early typical case, observing vacuolation and degeneration of vascular endothelial cells, with severe cases showing complete disappearance of the endothelial cell layer, leaving the vessel wall composed only of plasma and fibrous layers, surrounded by neuroglia.

Under light microscopy of advanced stage cases, the retina is extensively detached; the retina shows degeneration, atrophy, and complete structural destruction; the deep layers of the retina contain cysts of varying sizes, filled with hemorrhage and proteinaceous exudate; some also show dissipating ecchymosis, free pigment, varying numbers of foam cells, and cholesterol crystals. Retinal vessels are dilated, with thickened walls and hyaline degeneration; PAS staining shows thickening of the subendothelial basement membrane, with endothelial cell hyperplasia and degeneration. Vessel occlusion can also be seen, with endothelial cell shedding or even complete disappearance, blood extravasation, and only the outline of the vessels remaining. Both inner and outer layers of the retina show neovascularization. Perivascular infiltration of inflammatory cells such as lymphocytes and large mononuclear cells is present. The vitreous contains proteinaceous exudate and a small number of lymphocytes and large mononuclear cells, with some specimens also showing hemorrhage and cholesterol crystal spaces. At the adhesion sites between the choroid and retina and near organized connective tissue masses, there is significant chronic inflammatory cell infiltration. Connective tissue masses of varying sizes are located between the retina and choroid. Retinal pigment epithelial hyperplasia extends into the connective tissue masses. Some cases may show calcification or ossification. Cholesterol crystal spaces and foreign body giant cell reactions can also be seen.

In cases with secondary glaucoma, tissue specimens from the anterior segment of the eye show peripheral anterior synechia of the iris; the iris surface is covered with fibrovascular membrane; and the corneal epithelial basal layer shows edema.

bubble_chart Clinical Manifestations

The patient's general physical examination showed no abnormalities. The vision of the affected eye is not affected before the macula is damaged. There are also no other discomforts. The anterior segment of the eyeball is negative. The refractive media are clear, and the optic disc is normal or slightly congested. Large exudative patches on the retina are commonly seen in the posterior pole of the fundus, but can also occur in any other location. The size of the patches varies, they can be single or multiple, irregular in shape, white or yellowish-white, elevated beneath the retinal vessels, and occasionally may cover part of the vessels. The degree of elevation varies greatly, from not obvious to more than ten D. Dark red hemorrhages are often seen around the exudative patches, along with scattered or ring-shaped deep white spots. On the surface of the patches, shiny dots (cholesterol crystals) can be seen, and sometimes there is pigmentation. Both the arteries and veins of the retina show significant damage, manifested as filling and dilation of the first and second branches, thinning of the small branches beyond the second or third level, with white sheaths around them, and the lumen showing spindle or spherical dilation, or twisting, and there may be new blood vessels and anastomoses between blood vessels, etc. Vascular abnormalities are the basis for large exudates and hemorrhages under the retina. Microcirculation disorders cause localized or widespread gray-white edema in the retina, and the macula may have star-shaped spots. In the slow and prolonged course of the disease, the above changes appear alternately, with the condition sometimes mild and sometimes severe, eventually developing into total retinal detachment, which is hemispherical and appears as a dull light brown or light green. In some cases with a large amount of subretinal hemorrhage, the blood enters the vitreous body, and after organization, proliferative vitreoretinopathy is formed. Some cases may also develop complications such as internal visual obstruction, anterior uveitis, secondary glaucoma, or low intraocular pressure.

Fundus fluorescein angiography shows that the larger branches of the arteries and veins in the lesion area are dilated and tortuous; the capillary bed is occluded; there are microaneurysms on the surrounding capillaries or terminal small vessels; sometimes there are shunts between arteries and veins. In the early stage of angiography, the background fluorescence at the site of subretinal hemorrhage is masked, and large exudative patches show pseudo-fluorescence. In the advanced stage of angiography, there are exudative fistula disease and tissue staining.

bubble_chart Treatment Measures

Since the cause of the disease is unknown, there is currently no effective treatment. Laser photocoagulation and diathermy coagulation have some effect on early-stage cases with localized lesions by sealing the affected blood vessels, allowing the retinal edema and exudation to gradually absorb. However, the long-term efficacy remains uncertain. For advanced stages with extensive retinal detachment, some have used subretinal fluid drainage combined with diathermy coagulation and scleral shortening, which is said to halt the progression of the disease.

bubble_chart Differentiation

This disease should be differentiated from retinoblastoma (especially the exophytic type), metastatic endophthalmitis, and other eye diseases that occur in childhood and present with leukocoria.