Analysis of visual toxicity after gamma knife radiosurgery for treatment of choroidal melanoma: identification of multiple targets and mechanisms of toxicity.

OBJECTIVES: Identification of the targets of radiation damage after radiosurgical treatment of ocular melanoma will potentially allow for sparing of vision with improved treatment planning.
MATERIALS AND METHODS: Six patients with ocular melanoma, who had useful vision before therapy, were treated with gamma knife stereotactic radiosurgery with curative intent. Dosimetric analysis of functional targets of radiation damage including the fovea, optic nerve, lens, and iris was carried out. Serial testing of visual acuity and fundoscopic examination were carried out after treatment.
RESULTS: Visual sparing was achieved in 3 of 6 patients at last followup with a median follow-up of 2 years. The causes of loss of vision in those patients who lost useful vision were retinal detachment, neovascular glaucoma, and optic neuropathy.
CONCLUSIONS: Preradiosurgical size and location are likely predictors of posttreatment visual outcomes.