In Chapter 6, the first aim was to assess the development of RON in our cohort of patients with non-functioning pituitary adenomas, who received radiation therapy in the time period 1985 – 1998. Ophthalmological and imaging data of 72 patients with a minimum follow-up of 18 months after radiation therapy were retrospectively checked. The median follow-up was 51 months. The total radiation dose applied varied between 45 and 55.8 Gray with a daily dose varying from 1.8 to 2 Gray. No RON was diagnosed in these 72 patients. One of the 72 patients had spiralling isopters on Goldman perimetry without visual acuity loss 11 years after radiation therapy. This patient was initially considered as atypical RON, but the visual fields ultimately normalized and the diagnosis was rejected.
The second aim of this study was to determine the incidence of RON in reported series of non-functioning pituitary adenomas in relation to risk factors, based on a literature review. We performed a literature search, using Medline and Embase, regarding the time period 1966 – 2003. Twenty seven series were found and our series was added. In 11 of 2063 irradiated NFA patients, RON was diagnosed, yielding a percentage of 0.53. Additional 14 case reports on RON in NFA could be retrieved. RON was bilateral in 56% and unilateral in 44% of reported patients. Only 16% of affected eyes had a residual visual acuity due to RON of more than 2/10, 52% of the affected eyes had no light perception anymore. The median time between radiation therapy and the development of RON was 11 months. Sixteen percent of patients had a latency time of more than 18 months with a maximum of 54 months. Thirty-three percent of patients with RON were irradiated with an assumed safe radiation schedule, as reported in Chapter 5. Older age has been considered as a possible risk factor, but our series suggest that age is not a strong risk factor for developing RON in NFA. No major gender predominance was found. Based on our series and the literature review RON should be regarded as a very rare complication after external beam radiation therapy for non-functioning pituitary adenoma, especially when using up-to-date radiation schedules.