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N. Zepkin, J. DeCastro, I. Thornton, R. H. Yeilding, R. W. Frey; Measurement of Temperature Rise in Porcine Crystalline Lenses from a Photodisruption Laser. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3837.
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© ARVO (1962-2015); The Authors (2016-present)
Ultra short pulsed lasers, such as femtosecond or picosecond lasers are known to produce smaller thermal energy than nanosecond laser pulses but it is not known whether such ultra short pulse lasers will still produce sufficient thermal energy to be harmful to the lens. Therefore we seek to measure the temperature rise inside a porcine lens due to irradiation using a photodissruption laser.
Eleven cultured porcine lenses, whose dimensions were approximately 11mm EQ by 7mm A/P were used which were sufficiently clear as measured visually using a low spatial frequency target behind the lens. The posterior lens capsule was pierced with a scalpel and a 1mm diameter thermocouple probe was inserted into the center of the posterior of the lens approximately 2mm above the posterior pole. The thermocouple was compared to a known, recently calibrated immersion probe and was within 0.2 degrees C for the experimental temperature range. 1.064um wavelength ultrashort pulsed laser shots were fired in a pattern 6mm in diameter and 3mm in A/P immediately above the thermocouple. Approximately 500mW average power was used in 10 lenses with 6 of the lenses receiving 7 seconds of treatment duration and 4 of the lenses receiving 22 seconds of treatment duration. One lens received a factor of 3 times the energy and average power required for reliable photodissruption. Temperature measurements were taken continuously for up to 2 minutes.
The results indicate an average of less than 1 degree temperature rise (range of 0 to 2 degrees) for the 500mWatt irradiation for 7 seconds duration and less than 3 degree temperature rise (range of 2 to 3 degrees) for the 22 second treatment. In all cases the lens returned to within 1 degree of the initial temperature within 10 seconds after treatment ended. The 3 times normal energy/power caused a 5 degree maximum temperature rise, but returned to within 1 degree of the initial within 5 seconds after treatment ended.
Ultra short pulsed lasers in the vicinity of 500mWatt average power range do not significantly cause temperature rise inside the crystalline lens.
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