For surgical treatment of thyroid-related eye disease, many times we tell patients that it is best to wait until the disease is stable, so how do we determine whether the disease is active or not? A common clinical standard is called the CAS scale. Based on the clinical manifestations of the active phase (ocular pain, redness, edema and functional impairment of the eye), a clinical activity scale ( CAS) scale was developed as follows: Score Symptom 1 Spontaneous retrobulbar pain 1 Pain with eye movement 1 Redness and congestion of the eyelid 1 Diffuse congestion and redness of the conjunctiva 1 Eyelid edema 1 Bulbar conjunctival edema 1 Lacrimal caruncle edema 1 Increase in proptosis of more than 2 mm within 1-3 months 1 Within 1-3 months Decrease in eye mobility by more than 5 degrees in any direction 1 within 1-3 months and decreased visual acuity The activity score is the sum of the points of each clinical manifestation, and generally speaking a total score ≥4 is called a clinically active period. If the score is higher, the more active it is. Studies have shown that high CAS values tend to predict good treatment outcomes, while low CAS values do not indicate ineffective treatment. It has been suggested that the specificity of this assessment for predicting TAO activity is 86%.