Inclusion Criteria:  Clinical diagnosis of Grave's ophthalmopathy angle of deviation more than 20° clinically and biochemically euthyroid for at least 3 months; a stable orthoptic examination for at least 3 months, for example no greater than five prism dioptre change in primary position and no greater than an 8° change in duction monocular and mainly single extraocular muscle restricted motility  Exclusion Criteria:  Patients with suppression, previously diagnosed and/or treated strabismus not related to the thyroid best-corrected visual acuity (BCVA) less than 0.2 in one or both eyes