Is modified clinical activity score an accurate indicator of diplopia progression in Graves' orbitopathy patients?

The aim of this study is to describe characteristics of Graves' orbitopathy (GO) patients with progressive diplopia and to consider whether modified clinical activity score (CAS) is a useful indicator for prediction of diplopia progression. Medical records and images of GO patients with progressive diplopia were retrospectively reviewed. Clinical parameters (e.g., modified CAS, modified NOSPECS score, exophthalmometry results, score of diplopia, and prevalence of optic neuropathy) were evaluated. Thyroid stimulating hormone receptor autoantibody (TRAb) values were determined. Maximum recti muscle diameters and extraocular muscle (EOM) indices were evaluated. Sixty-three of the 435 GO patients had progressive diplopia; 44.4% (28/63) of these patients had a low CAS (<3). The subgroup analysis (by modified CAS, group 1: CAS<3, group 2: CAS >= 3) revealed that the mean modified NOSPECS score and exophthalmos value were significantly higher in group 2 (7.2, 19.1 mm) compared with group 1 patients (5.5, 17.7 mm) (p<0.001, p=0.037, respectively). Score of diplopia, prevalence of optic neuropathy and the positive rate and level of TRAb were not significantly different between groups. There were no differences in maximum recti muscle diameters or EOM indices between the two groups. Diplopia may progress even in patients with a low modified CAS. CAS may not reflect the inflammatory activity of myopathy, especially in mild to moderate GO with low NOSPECS and exophthalmos values. Careful patient follow-up using subjective and objective measures for diplopia should be performed.