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J. Shen, J. Kozub, R. Prasad, K. Joos; Optic Nerve Sheath Fenestration With a Raman-Shifted Mid-Infrared Laser (Tissue Study). Invest. Ophthalmol. Vis. Sci. 2009;50(13):1442.
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Optic nerve sheath fenestration is a treatment for vision loss in idiopathic intracranial hypertension not responding to medical management. Our previous studies suggest that endoscopic application with Free Electron Laser energy at 6.1 µm may be useful for minimally invasive orbital therapy including optic nerve sheath fenestration. This study proposes to make this technique more clinically feasible with substitution of a portable laser for the cost-prohibitive experimental Free Electron Laser (FEL).
The laser proposed for this study is a Q-switched, tunable alexandrite laser system, which provides a high-intensity, Q-switched output pulse of 50-100 ns at 10 pulses per second (Light Age, Inc.). It is wavelength-shifted by a two-stage stimulated Raman conversion process into the 6-7 µm range. Ten fresh cadaver porcine optic nerves were lased with 6.1 µm at 0.6 mJ with a 100 µm diameter spot. Besides linear incisions, a circular pattern was cut and the incised piece removed to form an optic nerve sheath window. Specimens were examined grossly and prepared for histological examination.
The table-top laser has a nearly Gaussian output and a narrow spectrum at 6.1 µm. The laser was capable of continuously incising the cadaver porcine optic nerve sheaths. Minimal thermal damage was evident.
A Q-switched, Raman-shifted tunable alexandrite laser system is capable of providing the parameters necessary for incision of an optic nerve sheath. This portable system will provide the translational advancement necessary to bring endoscopic laser surgery closer to clinical usefulness.
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