Finger’s “slotted” eye plaque for radiation therapy: treatment of juxtapapillary and circumpapillary intraocular tumours

Abstract

Aim: To create “slotted eye plaques” for the treatment of juxtapapillary and circumpapillary intraocular tumours.

Methods: Eye plaques were altered such that 8 mm-wide slots (variable length) were created to accommodate the orbital portion of the optic nerve. Thus, as the nerve entered the slot, the plaque’s posterior margin extended beyond the optic disc. Radioactive seeds were affixed around the slot, surrounding the juxtapapillary and posterior tumour margins.

Results: As proof of principle, three patients with choroidal melanomas that encircled or were in contact with the optic disc (considered untreatable with a notched eye plaque) were considered to be initial candidates for slotted-plaque radiotherapy. Preoperative three-dimensional C-scan imaging of their optic nerve sheath diameters insured that they would fit in the slotted plaque. Intraoperative ultrasound imaging was used to confirm proper plaque placement. Radiation dosimetry modelling showed that all tumour tissue received a minimum of 85 Gy (despite the gap created by the slot). With relatively short-term follow-up, there has been no evidence of ocular ischaemia, tumour growth or complications attributable to the use of slotted-plaque radiation therapy.

Conclusion: Slotted plaques accommodate the retrobulbar optic nerve into the device and thereby shift the treatment zone to improve coverage of both juxtapapillary and circumpapillary intraocular tumours.