Submacular Surgery for Selective Subretinal Delivery of Beta–radiation

Abstract

Abstract: : Purpose: To evaluate the feasibility and initial safety of selective (retinal–sparing) subretinal delivery of beta–radiation using a novel NeoVista brachytherapy system. Methods: Five dogs underwent pars plana vitrectomy surgery for selective subretinal delivery of strontium⁹⁰ beta–radiation using a novel radiation probe. The surgery included vitrectomy, creation of a subretinal bleb using a 41G needle, introduction of the brachytherapy probe in the subretinal space and controlled focal delivery of 26 Gy (single dosage) of beta radiation towards the subretinal tissue. The brachytherapy device contains shielding which prevent radiation exposure on the retinal side. Main outcome measures included changes in the fundus appearance, fluorescein angiography, OCT, ERG and histology (light microscopy and electron microscopy). The follow–up period was 1 month. Results: Selective subretinal delivery of 26 Gy was achieved in all eyes. The retina was completely reattached intraoperatively in all 5 animals. A rhegmatogenous retinal detachment developed post–operatively in 1 dog. In the remaining 4 dogs, no abnormalities were noted on biomicroscopy, fluorescein angiography, OCT, or ERG at 1 month after surgery. No significant changes in the retina, RPE/choriocapillaris/Bruch’s membrane complex, or choroid at the treatment site were evident by light microscopy at 1 month, compared to the fellow (non–treated) eye. Electron microscopic examination in two dogs also did not disclose any morphologic alternations in the retina, RPE/choriocapillaris/Bruch’s membrane complex, or choroid in the treatment zone. Conclusions: Selective, retina–sparing subretinal delivery of beta–radiation using the NeoVista brachytherapy system is feasible and appears to be relatively safe at one month. Further studies to evaluate its role in the treatment of subretinal diseases, such as exudative AMD, are warranted.

Keywords: radiation therapy • age–related macular degeneration • vitreoretinal surgery