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R.D. Robinson, J.H. Shen, L.A. Mawn, K.M. Joos; Optic Nerve Sheath Fenestration With Endoscopic Accessory Instruments versus the Free Electron Laser (FEL) . Invest. Ophthalmol. Vis. Sci. 2005;46(13):653.
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Purpose: Our previous studies showed that the Amide II wavelength (6.45 µm) produced by the FEL can efficiently produce an optic nerve sheath fenestration. The reaction of the tissue was similar whether the fenestration was produced by the FEL or by a scissors. In order to develop a minimally invasive approach, we compared available endoscopic accessory instruments to endoscopic FEL delivery to produce optic nerve sheath fenestrations. Methods: A 4.8 mm diameter endoscope (Olympus CYF–4A) with a 2.4 mm diameter instrument channel was used to perform optic nerve sheath fenestrations on exposed animal cadaver optic nerves. An endoscopic biopsy forceps, an endoscopic grasping forceps, a monopolar hot biopsy forceps, a 250 µm diameter hollow waveguide, and a 325 µm diameter hollow waveguide were inserted into the instrument channel for comparison. FEL energy (6.45 µm, 30 Hz) was delivered to the tissue through the hollow glass waveguides. The optic nerve was dissected from the globe and fixed in 3% paraformaldehyde, 0.1% glutaraldehyde, and 0.2% picric acid (v/v). Sections were examined with H&E. Results: Both the 250 µm and the 325 µm diameter hollow waveguide delivering FEL energy through the endoscope produced a complete circular optic nerve sheath incision with one pass. The 250 µm waveguide delivered up to 2.9 mJ and the 325 µm waveguide delivered up to 3.3 mJ. The standard biopsy forceps, the grasping forceps, and the monopolar biopsy forceps compressed the sheath tissue, but were unable to produce an optic nerve sheath fenestration. Conclusions: Endoscopic instruments currently available were unable to produce an optic nerve sheath fenestration. However, sufficient 6.45 µm FEL energy can be delivered through an endoscopic hollow waveguide surgical probe to produce an optic nerve sheath fenestration.
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