Degeneration of retinal ganglion cells after optic nerve sheath fenestration in an experimental rat model.

Background: Optic nerve sheath fenestration (ONSF) is a surgical procedure that is sometimes performed in patients with optic disc edema from increased intracranial pressure. The objective of this study was to assess the consequence of ONSF on optic nerve axons, retinal ganglion cells (RGCs), and retinal amacrine cells.

Methods: The optic nerves of 22 male Wistar rats were assigned to one of three groups. In Group 1 (n = 12), the rats underwent unilateral ONSF. In Group 2 (n = 10), the rat optic nerves were unilaterally exposed but were not operated on. Group 3 (n = 22) consisted of the optic nerves of Group 1 and Group 2 rats that were neither operated on nor exposed. Thirty days later, a cresyl violet staining method was used to assess the number and sizes of RGCs and amacrine cells. Optic nerve axons were assessed by means of glial fibrillary acidic protein (GFAP) immunoreactivity.

Results: ONSF was associated with a significant reduction (P < 0.05) in the number and size of RGCs and amacrine cells. Optic nerve axons were undisturbed.

Conclusions: Although ONSF does not apparently injure the optic nerve axons, loss and shrinkage of RGCs is a caution when considering ONSF as a treatment.