Optic nerve sheath fenestration with a novel wavelength produced by the free electron laser (FEL).

BACKGROUND AND OBJECTIVE To determine whether 6.45-microm free electron laser (FEL) energy can successfully perform optic nerve sheath fenestration and to compare the acute and chronic cellular responses with this surgery. STUDY DESIGN/MATERIALS AND METHODS Optic nerve sheath fenestration was performed in rabbits by using either FEL energy (< 2.5 mJ, 10 Hz, 325-microm spot size) or a knife. The optic nerve integrity and glial response were evaluated histologically acutely or 1 month postoperatively. RESULTS The FEL at low energy effectively cut the optic nerve sheaths with minimal reaction in the underlying nerve. With FEL or knife surgical techniques, a mild astrocytic hypertrophy only adjacent to the fenestration was observed acutely in the glial fibrillary acidic protein (GFAP) -immunoreacted sections. The chronic healing responses after either technique appeared similar with: (1) a thin fibrous scar at the fenestration site, (2) cells uniformly distributed (hematoxylin and eosin), and (3) up-regulation of GFAP and S100beta in astrocytes adjacent to the fenestration site. CONCLUSION The FEL at low energy performs an optic nerve sheath fenestration in a small space with ease. Both FEL and knife incisions cause a similar rapid glial response near the fenestration site that remains 1 month later.