The effect of retrobulbar irradiation on exophthalmos, ductions and soft tissue signs in Graves' ophthalmopathy: a retrospective analysis of 90 cases

PURPOSE: Retrospective analysis of the effect of retrobulbar irradiation on exophthalmos, ductions and soft tissue signs in patients with Graves' ophthalmopathy.

METHODS: We analysed the charts of 111 consecutive patients who were treated with retrobulbar irradiation according to standardised intake criteria between 1992 and 1997. After exclusion of patients who underwent other treatment (with steroids or orbital decompression) shortly before or within 6 months after irradiation, and on whom insufficient data were available, 90 patients were included. For these 90 patients, we analysed the exophthalmometry, ductions, soft tissue signs and visual acuity shortly before irradiation and after 3 and 6 months, respectively.

RESULTS: In the whole group, the Hertel value was on average 22 mm (SD 2.9) both before irradiation and after 3 and 6 months of follow-up. Separate analysis of data on 25 patients with bilateral exophthalmos of more than 24 mm also revealed no change in exophthalmos at follow-up. In the whole group, both abduction and elevation had improved by about 1 degree (SD 6.6 degrees; p = 0.05) after 3 months. This improvement has little clinical significance. In a subgroup of 14 patients who showed more than 10 degrees of restricted eye motility in one or more directions, both abduction and elevation had increased by about 4 degrees (SD 10 degrees; p = 0.02) at 3 and 6 months follow-up. Soft tissue signs had improved at 6 months after irradiation. We found no change in visual acuity after irradiation.

CONCLUSION: Retrobulbar irradiation in Graves' ophthalmopathy does not seem to reduce exophthalmos. It probably improves eye motility in patients with severe restrictions. The late improvement in soft tissue signs may either be a late effect of irradiation or be related to the natural history of the disease.