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A. Agarwal, V. Casagrande, J. Shen, K. M. Joos; Use of Free Electron Laser (FEL) to Perform Retinotomies. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5756.
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Previous studies have demonstrated the ability of the FEL at Amide II band (6.45 µm) to incise tissue with minimal collateral damage. We investigated the ability of the 6.45 µm and the 7.7 µm (Amide III band) FEL in making retinotomies in monkeys.
One eye each of 2 monkeys was used. 6.45 µm and 7.7 µm FEL at various energy levels were applied in a grid like pattern in 4 quadrants of one eye of each monkey. Acute clinical findings and late histological appearances were analyzed.
Clinically, the 6.45 µm laser was able to create holes with both 0.6 and 1.0 mJ energy levels. Histologically, the holes were less than full thickness at 0.6 mJ energy, and full thickness with minimal adjacent thermal damage at 1.0 mJ energy. However, underlying sub-retinal pigment epithelial hemorrhage was seen with1.0 mJenergy. The 7.7 µm laser caused retinal whitening alone without creating a hole at 0.6 mJ, created holes at 1.3 mJ, and was too strong causing vaporization of tissue at 2.0 mJ, clinically. Histologically, the 7.7 µm laser at 0.6 mJ caused inner retinal coagulation alone with superficial retinal hemorrhage, and at 1.3 mJ created large holes with surrounding thermal damage.
The 6.45 µm Amide II FEL successfully creates small, full-thickness holes in monkey retina. However the energy is transmitted to the underlying retinal pigment epithelium and choriocapillaris causing bleeding in the choroid. Future studies will investigate the capability of this wavelength to perform retinotomies in detached retinas.
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