Use of bursts of 1.54-μm microsecond laser pulses for cataract destruction

Abstract

The possibility of using bursts of microsecond pulses of an Yb,Er : glass laser (λ = 1.54 μm) for cataract destruction was investigated experimentally in vitro for the first time. The energy in a laser pulse was limited from below by the eye lens destruction threshold and from above by the radiation resistance of the input end face of the radiation-supplying fibre. The energy of a burst consisting of three microsecond laser pulses, separated by time intervals of 850 μs, was 255 ± 15 mJ, and the burst repetition rate was 15 Hz. The hydroacoustic signal, generated after each burst pulse in the water around the lens, contained two components. The first occurred immediately after the laser pulse transmission, and the second was delayed by 250 to 350 μs. The amplitude of the second component of the hydroacoustic signal exceeded the amplitude of the first component and was maximum (50.0 ± 8.0 MPa) for the signal induced by the second pulse in the burst. The efficiency of cataract destruction by microsecond-pulse bursts generated by an Yb,Er : glass laser was found to depend on the lens nucleus density, to exceed significantly the efficiency of cataract destruction by single microsecond pulses of this laser, and to be comparable with the efficiency of eye lens destruction by a 1.44-μm Nd : YAG laser.