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.
Department of Ophthalmology, Duke University School of Medicine, Durham, NC, USA.
Marcin P
MP
Czajka
Thomas J
TJ
Cummings
Brooks W
BW
McCuen
Cynthia A
CA
Toth
Hoang
H
Nguyen
Sharon
S
Fekrat
D000818:Animals; D001369:Axons / Q000473:pathology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005911:Gliosis / Q000209:etiology / Q000473:pathology; D006487:Hemostasis; D007124:Immunoenzyme Techniques; D007429:Intraocular Pressure; D016900:Neurofilament Proteins / Q000378:metabolism; D013508:Ophthalmologic Surgical Procedures; D009887:Ophthalmoscopy; D009898:Optic Disk / Q000473:pathology / Q000601:surgery*; D009900:Optic Nerve / Q000473:pathology / Q000601:surgery*; D012166:Retinal Hemorrhage / Q000209:etiology / Q000473:pathology; D012170:Retinal Vein Occlusion / Q000601:surgery*; D013552:Swine
D005904:Glial Fibrillary Acidic Protein; D016900:Neurofilament Proteins