Increased retinal blood flow in patients with Graves' disease: influence of thyroid function and ophthalmopathy

Objective: Graves' ophthalmopathy (GO), resulting from the inflammation of retro-orbital tissue, is one of the major complications of Graves' disease (GD). We investigated the clinical usefulness of the measurement of retinal blood flow (RBF) in the evaluation of GO and its activity. Measurement: RBF was quantitated by pulsed Doppler mode at just below the b ranch of central retinal artery, from which the resistance index (RI) was c alculated. Patients: Forty-seven euthyroid GD patients and 70 gender- and age-matched normal controls were measured for RI to investigate the effect of GO on RBE To investigate the effect of hyperthyroidism, 20 GD patients were measured for RI changes during antithyroid drug (ATD) therapy. Furthermore, 17 GD p atients with clinically overt GO were measured for RI changes during treatm ent with glucocorticoid plus retro-orbital radiation. Results: RI and exophthalmos showed a significant positive correlation in 4 7 treated euthyroid GD patients without clinically overt GO (r = 0.307, r < 0.05), but not in 70 age- and sex-matched normal subjects (r = 0.185, P = 0.161). Furthermore, RI, but not exophthalmos, significantly correlated wit h serum TSH receptor antibodies, an indicator for the disease activity of G O. ATD therapy significantly reduced RI in GD patients from 0.719 +/- 0.041 in the hyperthyroid state to 0.661 +/- 0.051 in the euthyroid state, but n ot to the levels observed in normal subjects having the similar exophthalmo s (0.640 +/- 0.049). The fractional reduction of RI during ATD therapy sign ificantly correlated with those of pulse pressure and ultrasonographic dist ensibility in carotid artery, but not with those of serum vascular injury m arkers, In 17 GD patients with clinically overt GO, all four patients havin g adipose tissue enlargement but not extraocular muscle hypertrophy (inacti ve GO) showed RI within the mean +/- 1 S.D. for treated GD patients without GO. In the other 13 GD patients having extraocular muscle hypertrophy (act ive GO), four and eight patients showed RI outside mean +/- 2 S.D. and mean +/- 1 S.D. respectively, Treatment with glucocorticoid plus radiation move d RI in 8 out of 10 patients toward the mean values of CD patients without GO, in spite of little improvement of exophthalmos. Conclusions: It was suggested that GD patients showed altered retinal hemod ynamics, possibly resulting either from the cardiovascular effect of hypert hyroidism or from retro-orbital inflammation, particularly in extraocular m uscle.