gms | German Medical Science

102. Jahrestagung der DOG

Deutsche Ophthalmologische Gesellschaft e. V.

23. bis 26.09.2004, Berlin

Retrobulbar irradiation for thyroid-associated orbitopathy: double-blind intra-individual comparison between 2.4 Gy and placebo

Meeting Abstract

Search Medline for

Evidenzbasierte Medizin - Anspruch und Wirklichkeit. 102. Jahrestagung der Deutschen Ophthalmologischen Gesellschaft. Berlin, 23.-26.09.2004. Düsseldorf, Köln: German Medical Science; 2004. Doc04dogSA.13.06

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Published: September 22, 2004

© 2004 Staubach et al.
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Retrobulbar irradiation is widely used in the treatment of thyroid-associated orbitopathy (TAO) because its hypothesized therapeutic mechanism - inhibition of lymphocytes and fibroblasts - is plausible. Recent controlled studies, however, question the benefit of retrobulbar irradiation and present conflicting opinions on indication and dosage. Mourits et al. (2000) found a reduction of diplopia after 20 Gy. Gorman et al. (2001) found no benefit of 20 Gy to one orbit as compared to sham irradiation of the fellow orbit, but there was collateral irradiation of the fellow orbit of up to 2 Gy, which possibly was effective. This hypothesis is supported by in vitro findings that demonstrate that lymphocytes and orbital fibroblasts are sensitive to radiation as low as 1 Gy. Prummel et al. (2004) demonstrated some benefit from 20 Gy in mild cases. Gerling et al. (2003) compared 16 Gy with 2.4 Gy and found no significant difference: either, retrobulbar irradiation is ineffective, or the maximal effect is reached already at 2.4 Gy.

Aim of the study

To distinguishing between the two above stated possibilities, under the hypothesis, that a dose as low as 2.4 Gy may be effective. The study will be the first double-blind trial to compare retrobulbar irradiation of a dose as low as 2.4 Gy with placebo. A standard therapy with 2.4 Gy would be extremely safe regarding optic neuropathy, retinopathy or induction of a tumour.


Patients with active TAO will be randomized and irradiated unilaterally; the fellow orbit will be sham-irradiated. The outcome measures (monocular motility, diplopia, orbital volume, patient complaints, clinical activity score) will be assessed at 6 months after intervention. To support the compliance of the participants, the first clinical visit will be offered at 6 weeks after intervention. The advantage of this approach over an inter-individual comparison is that randomization for known (and unknown) systemic influences like smoking, gender and concurrent steroid medication is not necessary. From a statistical standpoint, using the fellow orbit as an "internal" control, the validity of the data will be high.

Inclusion criteria

Age between 18 and 70 years; appearance of eye region typical of TAO; active disease according to a modified clinical activity score (CAS ≥ 4), history of hyperthyroidism and/or thyroid antibodies greater than normal values; euthyroidism at least during 3 months before intervention.

Exclusion criteria

TAO older than 9 months, previous radiotherapy of the eye region; previous steroid medication; previous thyroid resection or radioiodine; signs of optic nerve compression, serious eye disease other than TAO (e.g. cataract, glaucoma), diabetes mellitus.