Thyroid-associated ophthalmopathy is a complex pathology most of the time accompanying Graves' disease, also present in other thyroid states, such as Hashimoto's hypothyroidism and euthyroid states. The term Grave's disease associated ophthalmopathy can be misleading as it does not include all thyroid states associated to this eye condition. Its pathophysiology includes complex autoimmune mechanisms associated with fibroblasts, T-lymphocytes, myocytes, thyroid cells, adipocytes, and pro-inflammatory molecules, leading to several changes in the orbital content, including limitation of space, functional impairment, and complications secondary to the initial process. Reviewing its diagnostic methods and treatments is necessary due to new insights into the pathophysiology. The complexity of its pathogenesis is accompanied by a practical assessment and classification that allows clinicians to obtain significant amount of success when treating it.