Radial optic neurotomy in the porcine eye without retinal vein occlusion.

OBJECTIVE

To demonstrate the histopathologic changes in the porcine eye without retinal vein occlusion after radial optic neurotomy (RON).

METHODS

A RON was performed in 14 normal eyes of 12 Yorkshire Cross pigs. One radial stab incision at the edge of the nasal optic nerve head was made using a 20-gauge microvitreoretinal blade (Visitec) while the intraocular pressure was elevated. Surgery was concluded when hemostasis was achieved. Weekly ophthalmoscopic examinations were performed. Group 1 eyes (4 eyes of 2 pigs) were enucleated at the end of surgery. Group 2 eyes (4 eyes of 4 pigs) were enucleated 1 week postoperatively, and group 3 eyes (4 eyes of 4 pigs) were enucleated 3 weeks postoperatively. In group 4 (2 eyes of 2 pigs), animals underwent vitrectomy and RON, and eyes were enucleated 3 weeks postoperatively.

RESULTS

Ophthalmoscopic examination demonstrated engorged blood vessels at the RON site up to 3 weeks after surgery with minimal or no hemorrhage. Histological examination of the optic nerve demonstrated foci of hemorrhage, interstitial edema, reactive gliosis, and rare inflammatory cells. At 3 weeks, there was complete axonal nerve fiber loss distal to the neurotomy site.

CONCLUSIONS

After RON, marked gliosis and complete axonal nerve fiber loss occur at the neurotomy site. Although bleeding was rare intraoperatively in this porcine model, hemorrhage and interstitial edema were present within the optic nerve at the neurotomy site histologically. Clinical Relevance Radial optic neurotomy remains a controversial method of treatment for central retinal vein occlusion. To our knowledge, this is the first study in the literature describing the histopathologic findings after RON.