Chronic and Acute Optic Nerve Sheath Fenestration in Monkeys Using the Free Electron Laser (FEL)

(Wrk-P-3-08)

K.M. Joos, J.H. Shen, L. Mawn, D.J. Shetlar, M.K. Powers, V.A. Casagrande Prevent Blindness, Inc.  

Vanderbilt University

Our previous study using rabbits showed that the Amide II wavelength (6.45 $\mu$m) produced by the FEL could efficiently produce an optic nerve fenestration with minimal damage. In order to determine if this technology could eventually be applied to human surgery, we compared the results of producing fenestrations with the FEL or a knife in monkeys. Methods: Optic nerve sheath fenestration was performed with either the FEL (6.45 $\mu$m, 10Hz, 2-3mJ) through a hollow waveguide surgical probe in 6 eyes or with a knife (2 eyes) . The monkeys survived one month with the fellow optic nerve operated acutely just prior to perfusion of the animals. Optic nerves were evaluated histologically with H&E, and antibodies to GFAP, S100B, and vimentin.

Results: Dural incisions were technically more efficient using the FEL. ERGs were normal following both types of incisions. The tissue responses using either method were similar following either chronic or acute incisions. Conclusions: The FEL energy at 6.45 $\mu$m delivered through a hollow waveguide appears capable of efficiently and safely producing an optic nerve fenestration without direct damage to the nerve and with minimal glial reaction indicating that it could be a beneficial alternative for use in human surgery.