Fundus and histopathological study of radial optic neurotomy in the normal miniature pig eye.

OBJECTIVE To demonstrate the fundus and histopathological changes in the normal miniature pig eye after radial optic neurotomy. METHODS Ophthalmoscopic examinations, fundus photography, and fluorescein angiography were performed on 12 eyes that underwent radial optic neurotomy, 5 normal eyes, and 7 eyes that underwent vitrectomy (from 12 pigs in total) preoperatively and 1, 7, 14, 30, and 90 days postoperatively. These eyes were enucleated 120 days postoperatively. Sixteen eyes (of 8 pigs in total) that underwent radial optic neurotomy were enucleated 1, 3, 7, and 48 days (2 pigs each time) postoperatively. The enucleated eye sections were stained with hematoxylin-eosin, Masson trichrome, and Luxol fast blue. RESULTS The retina radial to the site of radial optic neurotomy darkened gradually with the increasing curvature of the major retinal arteries. The filling time intervals from the retinal artery to the retinal vein were prolonged. At the incision site, there was a loss of nerve fibers, which were subsequently replaced by collagenous tissue. No anastomotic vessels formed by the end of the study. CONCLUSIONS Postoperatively, the retinal circulation seemed somewhat sluggish compared with that seen preoperatively. Segmental retinal nerve atrophy eventually formed. The procedure itself may not be the sole factor for the formation of shunt vessels. CLINICAL RELEVANCE To date, radial optic neurotomy is controversial and persuasive animal studies are lacking. In combining fluorescein angiography with histopathological examination, this study may be somewhat helpful.