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H. Lubatschowski, H. Hoffmann, H. Hahn, T. Ripken, M. Fromm; Analysis of the Thermal Induced Damage of the Ocular Fundus During the Fs- Treatment of the Crystalline Lens. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4272.
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The aim to cut crystalline lens tissue either to treat presbyopia or cataract is a current field of research. During fs-lentotomy femtosecond laser pulses are used to induce incisions inside the crystalline lens to increase the flexibility of the lens tissue (presbyopia reversal) or to remove the lens (cataract). Thereby residual divergent radiation propagates through the vitreous and will be absorbed by the retinal fundus. As a consequence the laser energy could heat up the retina which might be a risk of safety and has to be excluded.
To produce a visible lesion (threshold ED50) on the retina a 100 kHz fs-laser system (wavelength 1040 nm, pulse duration 500 fs, pulse energy 38 µJ) was used. During the experiments the eye globes were fixed in a chamber filled with water with a temperature of 38°C. To verify the experimental results the threshold values of a pig eye model were simulated on a computer model.
Both, the experimental and the theoretical investigations showed a threshold of retinal damage ED50 in the range of 35 W/cm² at radiation times between 5 and 25 seconds.
The estimation of the threshold of the retinal damage of the pig eye is an important step on the way to evaluate the retina safety during the fs-lentotomy process. Based on the currently known parameter sets which might be of clinical relevance, fs-lentotomy does not induce thermal damages on the retina.
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