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K. M. Joos, R. Prasad, J. Kozub, J. Shen; Retinectomy with a Raman-Shifted Q-Switched Alexandrite Laser Retinal Handpiece. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4276.
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We have demonstrated that a wavelength at 6.1 µm produced by an experimental Raman-shifted Q-switched alexandrite laser system is capable of ablating tissue, including retina, with a minimal amount of collateral damage. We propose that an intraocular hollow-glass waveguide delivery probe can be developed to deliver the laser energy to the retina.
An alexandrite laser system, which provides a high-intensity Q-switched pulse (770-780 nm, 100 ns duration, 10 Hz), is wavelength-shifted by a two-stage stimulated Raman conversion process into the 6-7 µm range (Light Age, Inc.). A 250 µm diameter hollow-glass waveguide was used to develop a 25-gauge retinal handpiece. The vitreous was removed from 12 fresh cadaver porcine retinas. The retinas were lased with 6.1 µm delivered through the handpiece. Specimens were examined grossly and prepared for histological examination.
The 6.1 µm energy transmission was 30% through the 1.5 meter long waveguide and handpiece. The useful energy output from the handpiece ranged from 0.4 - 0.7 mJ with a 200 µm diameter spot. A full-thickness retinal incision with minimal thermal damage was obtained. The incision depth ranged from an incomplete incision to a full-thickness incision involving the underlying retinal pigment epithelium in the attached retinas.
The 6.1 µm mid-infrared energy delivered by a hollow-glass waveguide probe is capable of incising retinas with minimal thermal damage. However, the precision of the incision will be enhanced with coupled imaging to detect when the desired incision depth has been achieved to avoid over-treatment.
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