When reviewing reported cases of RON in acromegalic patients in whom total radiation dose and fraction size are reported (Table 2) –using the abovementioned search method – it appears that in 24 of 32 patients, in whom visual loss was specified, RON was bilateral in 17 patients (71%) and unilateral in seven patients (29%). Visual acuity was less than 2/10 in 35 of 41 RON affected eyes.
It is generally proposed, that most cases of RON occur within 18 months after radiation therapy49. However, Table 2 shows that in eight of 30 patients (27%), RON developed more than 18 months after radiation therapy (median 12 months, range 5-120 months). Thus late development of RON can occur, indicating that the clinician should remain alert of this complication, even many years after radiation therapy.