The paper discusses the influence of time profile of microsecond Yb,Er:Glass laser pulse on removal efficiency of cataract lens when performing its laser hydroacoustic processing. It was established that the increase in peak power of the "leading" spike of Yb,Er:Glass microsecond pulse leads to increase in volume of laser-produced steam-gas cavities in liquid, increase in pressure transient amplitude arising in the phase of "collapse-rebound" of the cavity and increase in removed volume of cataract lens as a result of its laser hydroacoustic processing (LHP). Increasing the peak power of the "leading" spike by 2.5÷3 times while keeping the total integral laser pulse energy resulted in a 5÷7-fold increase in the removed volume of human eye lens with III degree of cataract according to L. Buratto classification. The possible multipulse mechanism of cataract lens removal when performing LHP with microsecond Yb,Er:Glass laser pulses is discussed.
Laser microperforation of a human nail plate is an effective method to increase the speed of local drugs delivery in the treatment of nail diseases. In this paper we present the study results of the influence of spatial parameters of Er:YLFlaser- produced microhole array in human nail plate (the diameter of microholes and their packing density) on the rate (vsp) of 0.25 % water-alcohol solution of methylene blue penetration through a single microhole and on the time (Tmp) required for uniform distribution of this drug under the nail plate. In experiments, the diameter of microholes was 220 ± 10 μm, 300 ± 10 μm or 350 ± 10 μm. The packing density for microholes of each of these diameters was 100 μholes/cm2, 400 μholes/cm2 and 950 μholes/cm2. It is shown that vspis mainly determined by the microhole diameter, and the packing density does not have a significant influence on it. It was experimentally established that the rate vsp is maximal for microholes with 350 μm diameter at packing density of 950 μholes/cm2 and reaches a value of 6.3 μm/s, and the time Tmp is minimal and equal to 180 ± 10 s at the same values of microhole diameter and packing density.
The results of strobe-photographic study of steam-gas cavities formation in a bulk of saline as a result of high-power Yb,Er:Glass laser pulses impact are presented. The data on dynamics of laser pulse transmission through the laserproduced steam-gas cavity for different values of the distance h between the fiber end and the cuvette bottom (quartz plate) are presented. It was observed that the steam-gas cavity might be used for effective non-contact delivery of laser radiation to the submerged target: transmission value at maximum steam-gas cavity size reached 0.87 for h = 0.5 mm. The influence of steam-gas cavities parameters on ablation efficiency of eye lens destruction in vitro is also discussed. The ablation of cataract eye lens in liquid environment is more effective than in air. The efficiency of eye lens ablation decreases with the increase of h . The maximal values of ablation efficiency (2.14·10-3 mm3/pulse) were obtained in the case of underwater ablation at h = 0 mm.
The results of in vitro pilot study of anterior lens capsule destruction by submicrosecond pulses of Yb,Er:Glass laser as well as results of 2% agar gel damage threshold investigation are presented. It was established that the local destruction of anterior lens capsule is possible without any ruptures at energy densities up to 25 J/cm2 when exposed to 30 laser pulses, delivered via 200 μm optical quartz fiber. It was found that 2% agar gel damage threshold determined as minimal value of laser energy density required for appearance of the visually identifiable damage of agar gel decreases with the increase in the number of laser pulses. The 2% agar gel damage threshold on the air for a single laser pulse impact was about 2.3-3.3 J/cm2, for 5 pulses impact – about 1.8-2.5 J/cm2 and for 10 pulses impact – about 1.6-2.4 J/cm2.
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