Infrared free electron laser-tissue interactions with human ocular tissues
Purpose. To utilize the tuning capability of the Vanderbilt University Free Electron Laser (FEL) to examine ocular laser-tissue interactions with novel infrared wavelengths for potential improvement of ophthalmic laser surgical procedures. Methods. Human cadaver eyes were placed in 7.5% dextran solution to normalize corneal thickness, and solution was injected intraocularly to achieve a physiologic intraocular pressure. Ocular tissues including cornea, iris, retina and optic nerve were lased at the 2.94 μm water absorbancy peak, 6.0 μm amide I band, 6.1 μm water absorbancy peak, 6.45 μm amide II band, and 7.7 μm delivered through a hollow waveguide. The Vanderbilt FEL produces 5 μs long macropulses at 10 Hz with each macropulse consisting of 1 ps micropulses at 3 GHz. Results. Histologic examination of corneal tissue showed the least amount of collateral damage (10 - 20 μm) with the 6.0 μm amide I band, while marked shrinkage occurred with the 7.7 μm wavelength. For optic nerve tissue, the least amount of collateral damage (0 μm visible) occurred at 6.1 μm water absorbancy peak and 6.45 μm amide II band, while the most damage (25 - 50 μm) was observed with the 7.7 μm wavelength. Conclusions. A hollow waveguide is capable of delivering useful infrared energy to ablate ocular tissues. Different tissues may have different optimal wavelengths for surgical laser procedures, and the tunable free election laser has the unique capability to investigate those potentially useful wavelengths.
Joos, KM; Shen, JH; Edwards, GS; Shetlar, DJ; Khoury, JM; Robinson, RD
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