Commentary: Coats disease: Our experience in India.

Coats disease is one of the greatest mimickers in ophthalmology. The present study by Shield et al. has beautifully illustrated the changing pattern of clinical features, progression, management options, and outcomes over the past 45 years.[1] When compared with western literature, bilateral involvement is more commonly reported in Indian studies. A study by Rishi et al. has showed severe visual impairment and extensive four-quadrant involvement at initial presentation.[2] Atypical presentations such as anterior segment involvement, pain, or vitreous hemorrhage have also been reported in Indian eyes. A patient presenting with features of bilateral retinal exudation and telangiectasia must undergo thorough ocular and systemic evaluation. “Coats-line response” is a separate clinical entity characterized by exudative response in pathologies such as retinitis pigmentosa, pars planitis, senile retinoschisis, facioscapulohumeral dystrophy type 1, and Leber's congenital amaurosis.[3] Coats plus syndrome is a rare entity characterized by cerebral leukodystrophy, cysts, and associated calcification.[4] It can be associated with psychomotor developmental delay, seizures, intrauterine growth retardation, myelodysplasia, skeletal, and gut anomalies. Genetic testing reveals presence of mutation in conserved telomere maintenance component 1 (CTC1) gene.

Indian studies have shown a bimodal pattern in the age of disease onset, giving importance to adult-onset Coats disease.[25] It is a relatively benign form of the disease with limited area of involvement, more posterior involvement, slower progression of disease, and better response to therapy.[5] Ultra-widefield imaging has an immense role in such cases by better detection of vascular leakage, peripheral area of nonperfusion, and neovascularization.[3] This aids in better documentation and management. In smaller children, fluorescein angiography can be performed under general anesthesia using imaging systems like RetCam. These also provide a wide field of view and can help in proper delineation of the aneurysms/telangiectasia and capillary nonperfusion areas for targeted application of laser photocoagulation.

An important differential of Coats disease is diffuse infiltrating retinoblastoma (DIRB). DIRB is a unilateral, sporadic variant affecting older age group of children characterized by horizontally growing ill-defined mass with minimal vertical growth. Clumps of calcification are rarely present; punctate calcification is characteristic. Calcification can also be found rarely in advanced cases of Coats disease. The clinical differentiation between retinoblastoma and Coats disease has been extensively highlighted in the present study.[1] The findings of ultrasonography, computed tomography scan, and contrast-enhanced magnetic resonance imaging should also be corroborated. If dilemma still persists, cases can undergo enucleation (in cases with no vision potential) or should be kept under close follow-up, which is difficult in Indian settings. Role of intraocular fine needle aspiration cytology has come up in such cases.[6] Risks of tumor spillage and extraocular spread should always be kept in mind. Advanced cases of Coat“s disease can also present with cholesterolosis bulbi in which yellow refractile crystals are present in anterior chamber. Histopathological diagnosis is definitive in cases of Coats disease which is characterized by the presence of foamy macrophages and cholesterol clefts.

Management of early stages can be done by observation, laser of telangiectatic vessels and areas of nonperfusion, as well as cryotherapy of lesions with associated subretinal exudation. Previously, vitreoretinal surgery was limited to cases of retinal detachment (RD). Nowadays, authors have obtained favorable outcomes in vitrectomy surgeries for secondary macular changes such as epiretinal membrane and macular hole.[7] Some surgeons have tried transscleral drainage of subretinal fluid followed by cryotherapy/laser in cases of exudative RDs.[8] Prognosis remains poor in advanced cases. Anti-VEGFs have a potential role in reduction of macular exudation. All these cases need a diligent follow-up due to chances of recurrence and possibility of development of neovascular glaucoma.