Patient's question:
Doctor, thank you for your concern. I have been diagnosed with Coats' disease at the hospital and have undergone two laser photocoagulation surgeries. I just don't know when this will end, and I am very frustrated. Can this disease be cured? / What should I do??Doctor's answer:
Outer Exudative Retinopathy (Coats' Disease) (exteralexudativeretiopathy,Coatsˊsdisease) was first reported by G. Coats in 1908, hence it is also known as Coats' disease. It is mostly seen in male adolescents, with fewer cases in females. A few cases occur in adults, even in the elderly. The ratio of juvenile patients to adult patients is approximately 4:1 (Woods, 1963). When seen in adults, it is referred to as adult-type Coats' disease, also known as multiple millet-like microaneurysms, which was previously reported by Leber in 1912. Coats' disease typically affects one eye, though it can occasionally affect both eyes. The course is slow and progressive, with early stages often going unnoticed (especially in pediatric patients), until significant vision loss, leukocoria, or disuse strabismus occurs.[Pathogenesis] The etiology of this disease is still unclear. The pathogenesis is associated with structural abnormalities of retinal vessels, where the barrier function of vascular endothelial cells is lost, leading to large-scale and multi-layered damage to retinal neural tissue and vascular structures. This results in a series of clinical changes. However, whether this retinal vascular abnormality is congenital or acquired, primary or secondary, remains undetermined.
[Clinical Manifestations] Physical examination of the patient shows no other abnormalities. Before the macula is affected, vision is unaffected, and there are no other discomforts. Anterior segment examination reveals no positive findings, with clear refractive media and a normal or slightly congested optic disc. Large exudative plaques are commonly found in the posterior pole of the retina but can also occur in any other location. The size varies, and they can be single or multiple, with irregular shapes, appearing white or yellowish-white and elevated below retinal vessels. Occasionally, they may cover part of the vessels. The elevation varies significantly, ranging from slight to over 10 diopters. Dark red hemorrhages are often seen around the plaques, along with scattered or ring-shaped deep white spots. On the surface of the plaques, small shiny spots (cholesterol crystals) may be observed, and sometimes pigmentation is present. Both arteries and veins in the retina are significantly damaged,、，，，，。 The abnormal vessels are the foundation for large-scale subretinal exudation and hemorrhage. Microcirculatory disturbances cause regional or widespread grayish-white edema in the retina, with a star-shaped spot in the macula. Over a slow and prolonged course, these changes alternate between new and old, with the disease worsening and eventually leading to retinal detachment. The detached area appears grayish-brown or bluish-gray. In some cases with extensive subretinal hemorrhage, the blood may enter the vitreous humor, forming a proliferative vitreoretinal membrane after organization. Some cases may also be complicated by cataracts, anterior uveitis, secondary glaucoma, or hypotony.
Fluorescein fundus angiography (FFA) shows dilated and tortuous large branches of arteries and veins in the affected areas, with occluded capillary beds. Around the occluded capillary beds, there may be microaneurysms in surrounding capillaries or small vessels. Arteries and veins may also show shunts. In the early phase of imaging, the background fluorescence is obscured at sites of subretinal hemorrhage, while large exudative plaques show pseudofluorescence. In the late phase, there is leakage and tissue staining.
[Pathology] Most histological examinations of this disease in the literature are of late-stage cases. Tripath and Ashto (1971) performed an electron microscopic examination of an early, typical case and observed vacuoles and degeneration in vascular endothelial cells. In severe cases, the endothelial cell layer was completely absent, leaving only glial tissue around the blood vessel wall. The exudate in the subretinal space had the same composition as plasma (Farkes, 1973). In late-stage cases examined under a light microscope, the retinal neural epithelium was widely detached. The neural epithelium contained cyst-like cavities of varying sizes, filled with bloody and proteinaceous exudate. Some cases also showed organized plaques, free pigment, varying numbers of foam cells, and cholesterol crystals. The retinal vessels were dilated, thickened, and hyalinized. PAS staining revealed thickened subendothelial basal membranes, endothelial hyperplasia and degeneration, and vessel occlusion. Endothelial cells may also be shed or completely absent, with blood extravasation leaving only vessel outlines. New vessels were observed both within and outside the neural epithelium. Inflammatory cell infiltration, including lymphocytes and large mononuclear cells, was seen around the vessels. The vitreous humor contained small amounts of proteinaceous exudate, along with lymphocytes and large mononuclear cells. Some specimens also showed gaps with hemorrhage and cholesterol crystals. Significant chronic inflammatory cell infiltration was observed near the choroid-retinal adhesion sites and around organized fibrotic tissue masses. The fibrotic tissue masses were of varying sizes and located between the retina and choroid. The retinal pigment epithelium was hyperplastic and extended into the fibrotic tissue masses. In some cases, calcification or ossification was present. Occasionally, foreign body giant cell reactions were also observed. In eyes with secondary glaucoma, anterior segment specimens showed peripheral anterior synechiae of the iris, a vascular membrane covering the iris surface, and edema of the corneal epithelial basal layer.
[Diagnosis] This disease should be differentiated from retinoblastoma, retinopathy of prematurity, and metastatic intraocular inflammation, which are eye diseases that occur in childhood and present with leukocoria. Among these, differentiation from retinoblastoma is particularly important, as misdiagnosing retinoblastoma as Coats' disease can delay treatment and endanger the child's life. Additionally, conditions such as central retinal vein occlusion and diabetic retinopathy may sometimes show findings under an ophthalmoscope that are extremely similar to Coats' disease (e.g., large yellowish-white exudates, microaneurysms, and cholesterol crystals), and may be referred to as Coats-like reaction.
[Treatment] Due to the unclear etiology, there is currently no effective drug treatment. Corticosteroids can promote edema and exudate absorption, providing temporary relief but failing to halt the progression. Laser photocoagulation is used in early stages when the lesion is still localized and there is no significant subretinal fluid accumulation. Argon-green laser is generally selected to close abnormal vessels (microaneurysms, fusiform arterioles, and capillary) to control exudation and promote absorption, with some effectiveness. For lesions in the periphery of the retina that are not satisfactorily treated with laser, cryopexy can be used as an adjunct. If there is significant subretinal fluid accumulation and widespread exudation, making laser photocoagulation ineffective, cryopexy or electrocoagulation may be necessary. Laser photocoagulation can also be performed after cryopexy. In late-stage cases with severe proliferative vitreoretinal membrane and extensive subretinal exudate accumulation, vitreoretinal surgery may be considered.