Blindness in patients after external beam irradiation for pituitary adenomas: two cases occurring after small daily fractional doses.

We report two cases of blindness occurring within 10 months of completion of radiation with 45 Gy in 1.80 Gy fractions given five times weekly. The literature on blindness as a complication of pituitary irradiation is reviewed. There have been no reported cases of total visual loss occurring as a consequence of treatment with fractional doses of less than 2 Gy. Visual loss due to radiation damage usually occurs within two years of completion of treatment in contrast to visual loss due to recurrence or empty sella syndrome, which usually occur more than two years after the completion of therapy. Other causes of blindness not related to the radiation, and potentially reversible, must be considered. However, these causes usually have a distinctively different clinical picture. Fraction size, total dose, and treatment time are all important factors when considering the biological effects of radiation to the pituitary region.