Radial Optic Neurotomy in the Porcine Eye Without Retinal Vein Occlusion

Objective To demonstrate the histopathologic changes in the porcine eye withoutretinal vein occlusion after radial optic neurotomy (RON). Methods A RON was performed in 14 normal eyes of 12 Yorkshire Cross pigs. Oneradial stab incision at the edge of the nasal optic nerve head was made usinga 20-gauge microvitreoretinal blade (Visitec) while the intraocular pressurewas elevated. Surgery was concluded when hemostasis was achieved. Weekly ophthalmoscopicexaminations were performed. Group 1 eyes (4 eyes of 2 pigs) were enucleatedat the end of surgery. Group 2 eyes (4 eyes of 4 pigs) were enucleated 1 weekpostoperatively, and group 3 eyes (4 eyes of 4 pigs) were enucleated 3 weekspostoperatively. In group 4 (2 eyes of 2 pigs), animals underwent vitrectomyand RON, and eyes were enucleated 3 weeks postoperatively. Results Ophthalmoscopic examination demonstrated engorged blood vessels at theRON site up to 3 weeks after surgery with minimal or no hemorrhage. Histologicalexamination of the optic nerve demonstrated foci of hemorrhage, interstitialedema, reactive gliosis, and rare inflammatory cells. At 3 weeks, there wascomplete axonal nerve fiber loss distal to the neurotomy site. Conclusions After RON, marked gliosis and complete axonal nerve fiber loss occurat the neurotomy site. Although bleeding was rare intraoperatively in thisporcine model, hemorrhage and interstitial edema were present within the opticnerve at the neurotomy site histologically. Clinical Relevance Radial optic neurotomy remains a controversial method of treatment forcentral retinal vein occlusion. To our knowledge, this is the first studyin the literature describing the histopathologic findings after RON.