Different Phenotypes and Ocular Surface Changes in Thyroid-Associated Orbitopathy

Thyroid associated orbitopathy (TAO) is an autoimmune disease which is heterogenous. Multiple drivers affect the disease in its clinical, radiological, and biochemical appearance. Patients do not always follow the classic activity and severity of the disease which may cause misleading clinical assumptions and conclusion of the disease. Therefore, it is crucial to classify the patient, in addition to the classical classifications, according to how the disease looks like, which refers to phenotype. Phenotype is a consequence of the interaction of the tissues and how the disease processes its response. There are six different phenotypes of TAO: (1) Congestive phenotype (2), White eye expansion, (3) White eye apex, (4) Hydraulic apex, (5) Cicatricial active and (6) Cicatricial passive. The clinical manifestations of those phenotypes and their response to the treatment modalities are different. Therefore, it is important to classify TAO patients according to this suggested phenotype classification, as this is the key to choosing the best treatment options and providing a best tailored treatment. In addition, TAO affects the ocular surface and causes dry eye disease. There are numerous factors for the pathogenesis of dry eye disease such as changes in tear volume, tear film osmolarity and instability, corneal sensitivity, and meibomian gland loss. Lubricants and anti-inflammatory drops can be used to treat dry eye disease among TAO patients.