A new technique for Nd:YAG laser posterior capsulotomy

AIM:To investigate the effects of a new opening pattern in neodymium:yttrium-aluminum-garnet(Nd:YAG)laser posterior capsulotomy on visual function.METHODS:This technique was conducted along a circular pattern.The energy ranged between 0.8 and1.2 mJ/pulse was consumed and mean total energy levels were 74±21 mJ(mean±standard deviation:SD,from 40 to167)and laser shots aimed at 150μm away behind a datum point and went along an imaginary line which extends 0.5 mm inside from optic margin and into the circular en bloc pattern.Vitreous stands were attached with fragment and then they were cut off by the laser after circular application.The circular fragment was completely separated from vitreous,and then this fragment was quickly sunk in intravitreal space.RESULTS:The follow-up period ranges from at least a week to 40mo,making 15.8mo on average.The procedural outcome showed 96%(74 eyes out of the 77eyes)enhancement in patients’visual acuity.Cystoid macular edema or retinal detachment was not observed in any of the patients during follow-up periods.CONCLUSION:This new technique is expected to improve the weaknesses that the conventional procedures have by adding the process to cut off vitreous stands attached with the fragment by the laser to the circular application.

Induction of oxidative stress in human aqueous and vitreous humors by Nd:YAG laser posterior capsulotomy

AIM： To evaluate whether the Q-switched Nd：YAG laser treatment applied in routine capsulotomy elicits oxidative stress in aqueous and vitreous humors. METHODS： Thirty-six patients who had to undergo a 25 gauge pars plana vitrectomy due to vitreoretinal disorders were enrolled, 15 of them underwent a Q-switched Nd：YAG laser capsulotomy 7 d before vitrectomy due to posterior capsule opacification（PCO）（Nd：YAG laser group） while the remaining 21 patients were not laser treated before vitrectomy（no Nd：YAG laser group）. Samples of the aqueous and vitreous humors were collected during vitrectomy from all patients for the assessment of oxidative parameters which were compared between the Nd：YAG laser group and no Nd：YAG laser group. Thiobarbituric acid reactive substances（TBARS）, a product of membrane lipid peroxidation, nitrite levels, the antioxidative activities of SOD and catalase, the 4-HNE-protein conjugate formation, indicating structural modifications in proteins due to lipoperoxidation, were assessed in aqueous and vitreous samples. RESULTS： In the human vitreous humor TBARS levels are significantly higher in the Nd：YAG laser group compared to the no Nd：YAG laser group and importantly, there is a significant correlation between the TBARS levels and the total energy of Nd：YAG laser used during capsulotomy.Moreover the anti-oxidative activities of SOD and catalase were significantly decreased by Nd：YAG laser treatment, both in aqueous and vitreous humors. In accordance with the TBARS data and anti-oxidative enzyme activities, significantly higher levels of proteins were conjugated with the lipoperoxidation product 4-HNE in the aqueous and vitreous humors in the Nd：YAG laser-treated group in comparison to no Nd：YAG laser group. CONCLUSION： These data, clearly suggest that any change that Q-switched Nd：YAG photo disruption may cause in the aqueous and vitreous compartments, resulting in a higher level of oxidative damage might be of considerable clinical significance particularly by accelerating the aging of the anterior and posterior segments of the eye and by worsening the intraocular pressure, the uveal, the retinal（especially macular） pathologies.

COMPARISON OF THE EFFECTIVENESS BETWEEN ANTERIOR CAPSULOTOMY WITH Nd:YAG LASER AND WITH BENT NEEDLE IN PATIENTS WITH CONGENITAL CATARACT

The effectiveness of capsulotomy with Nd:YAG laser and with bent needle were compared in 50 patients(66 eyes) with congenital cataract. There were 24 patients(32 eyes) in the laser group and 26 patients(34 eyes) in the needle group. There were not significant differences in sex, age, pre-operative visual acuity and intraocular pressures, and classification of cataract between the two groups. The results show that patients in the laser group have better post-operative visual acuity. The reason is YAG las...

Featuring the Nd:YAG laser capsulotomy in the operating room

Dear Editor,We read with interest the article of Kinori et al[1]titled’Pediatric Nd:YAG laser capsulotomy in the operating room:review of 87 cases’.Facilities for laser capsulotomy under general anesthesia are essential for young children and uncooperative patients undergoing cataract surgery.

Stability of neodymium:YAG laser posterior capsulotomy in eyes with capsular tension rings

·AIM: To evaluate the stability of neodymium(Nd):YAG laser posterior capsulotomy in eyes with capsular tension rings(CTRs).·METHODS: A total of 60 eyes that underwent cataract surgery and laser posterior capsulotomy postoperatively were included in this retrospective cohort study. To evaluate the safety and stability of capsulotomy, changes in the size of posterior capsulotomy and anterior chamber depth(ACD) in three groups: the group without CTR, the group with 12 mm CTRs, and the group with 13 mm CTRs, at 1wk, 3, 12, and 15mo after capsulotomy, were compared. ·RESULTS: In the group without CTR and the group with 12 mm CTR, there was no significant change in ACD at every post-laser follow-up. In the group with 13 mm CTR, the ACD change was significant until 3mo after capsulotomy. In all groups, there was a significant increase in the area of capsulotomy between 1wk and 3mo post-laser. Between 3 and 12mo post-laser, only the group with 13 mm CTR showed a significant increase in the area of capsulotomy(P<0.01). ·CONCLUSION: Laser posterior capsulotomy is safe in all three groups. The capsulotomy and ACD become stabilized and have not shown significant changes since 1y postlaser, even with larger CTRs. The maintenance of centrifugal capsular tension can last longer with larger CTRs, and the stability of the capsulotomy site can be reached about 12mo after capsulotomy in pseudophakic eyes with larger CTRs.

A 526 mJ Subnanosecond Pulsed Hybrid-Pumped Nd：YAG Laser

A hybrid-pumped Nd：YAG pulse laser with a double-pass two-rod configuration is presented. The focal length of offset lens is particularly studied to compensate for the thermal lens effect and depolarization. For input pulse energy of 141 μJ with pulse duration of 754ps, the pulse laser system delivers 526mJ pulse energy and 728ps pulse width output at lO Hz with pulse profile shape preservation. The energy stability of the laser pulse is less than 3%, and the beam quality factor M2 is less than 2.26.

Nd:YAG water mist laser treatment for giant gestational gingival tumor: A case report

BACKGROUND This case of gestational gingival tumor is huge and extremely rare in clinical practice.As the growth location of this gingival tumor is in the upper anterior tooth area,it seriously affects the pregnant woman's speech and food,causing great pain to the patient.The use of Nd:YGA water mist laser to remove the gingival tumor resulted in minimal intraoperative bleeding,minimal adverse reactions,and good postoperative healing,which is worthy of clinical promotion and application.CASE SUMMARY The patient,a pregnant woman,reported a large lump in her mouth on the first day of postpartum treatment.Based on medical history and clinical examination,the diagnosis was diagnosed as gestational gingival tumor.Postoperative pathological biopsy also confirmed this diagnosis.The use of Nd:YAG water mist laser to remove the tumor resulted in minimal intraoperative bleeding,clear surgical field of view,short surgical time,and good postoperative healing.CONCLUSION In comparison to traditional surgery,Nd:YAG water mist laser surgery is minimally invasive,minimizes cell damage,reduces bleeding,ensures a clear field of vision,and virtually eliminates postoperative edema,carbonization,and the risk of cross infection.It has unique advantages in oral soft tissue surgery for pregnant patients.Therefore,the clinical application of Nd:YAG water mist laser for the treatment of gestational gingival tumors is an ideal choice.

Clinical usefulness of transpapillary removal of common bile duct stones by frequency doubled double pulse Nd:YAG laser

AIM: To study the efficacy and the safety of laser lithotripsy without direct visual control by using a balloon catheter in patients with bile duct stones that could not be extracted by standard technique. METHODS: The seventeen patients (7 male and 10 female; mean age 67.8 years) with difficult common bile duct (CBD) stones were not amenable for conventional endoscopic maneuvers such as sphincterotomy and mechanical lithotripsy were included in this study. Laser wavelengths of 532 nm and 1064 nm as a double pulse were applied with pulse energy of 120 mJ. The laser fiber was advanced under fluoroscopic control through the ERCP balloon catheter. Laser lithotripsy was continued until the fragment size seemed to be less than 10 mm. Endoscopic extraction of the stones and fragments was performed with the use of the Dormia basket and balloon catheter. RESULTS: Bile duct clearance was achieved in 15 of 17 patients (88%). The mean number of treatment sessions was 1.7 ± 0.6. Endoscopic stone removal could not be achieved in 2 patients (7%). Adverse effects were noted in three patients (hemobilia, pancreatitis, and cholangitis). CONCLUSION: The Frequency Doubled Double Pulse Nd:YAG (FREDDY) laser may be an effective and safe technique in treatment of difficult bile duct stones.

芪参补气活血养颜汤联合Q开关Nd∶YAG激光治疗女性黄褐斑的美学效果观察

目的:探讨芪参补气活血养颜汤联合Q开关Nd∶YAG激光治疗女性黄褐斑的美学效果。方法:选取笔者医院2019年1月-2022年1月收治的80例黄褐斑女性作为研究对象,按照随机数字表法分为观察组42例(采用芪参补气活血养颜汤联合Q开关Nd∶YAG 1064 nm激光治疗)和对照组38例(采用Q开关Nd∶YAG 1064 nm激光治疗)。观察两组的临床疗效,中医症状积分,皮肤状况,黄褐斑面积及颜色,不良反应发生率。结果:治疗后,观察组患者的总有效率为97.62%,高于对照组患者的84.21%(P<0.05)。治疗后,观察组患者情绪低落、胸胁胀痛、经行乳胀、口苦咽干等上述中医症状积分均低于对照组患者(P<0.05)。治疗后,观察组黑素指数、红斑指数及皱纹指数均低于对照组(P<0.05)。治疗后,观察组黄褐斑面积及颜色评分均低于对照组(P<0.05)。治疗后,观察组患者的总不良反应发生率与对照组患者比较差异无统计学意义(P>0.05)。结论:芪参补气活血养颜汤联合Q开关Nd∶YAG1064 nm激光能够提高黄褐斑治疗的临床疗效,改善患者临床症状,改善皮肤状况,减少黄褐斑面积及颜色,安全性较高,值得临床推广。

Pulsed Nd:YAG laser cladding of high silicon content coating on low silicon steel

A pulsed Nd：YAG （yttrium aluminum garnet） laser-based technique was employed to clad low silicon steel with preplaced Si and Fe mixed powders for high Si content. The surface morphology, microstructural evolution, phase composition, and Si distribution, within the obtained cladding coatings, were characterized by optical microscopy （OM）, field emission scanning electron microscopy （FE-SEM）, with associated energy dispersive spectroscopy （EDS）, transmission electron microscopy （TEM）, and X-ray diffraction （XRD）. The microhardness was also measured along the depth direction of the specimens, A crack- and pore-free cladding coating through excellent metallurgical bonding with the substrate was successfully prepared on low silicon steel by means of optimized single-track and multi-track laser cladding. The phases of the coating are a-Fe, T-Fe, and FeSi. The high microhardness of the lasercladding zone is considered as an increase in Si content and as the refined microstructure produced by the laser treatment. The Si contents of the cladding coatings were about 5.8wt% in the single-track cladding and 6.5wt% in the multi-track cladding, respectively.

Effects of 946-nm thermal shift and broadening on Nd^(3+):YAG laser performance

Spectroscopic properties of flashlamp pumped Nd^3＋：YAG laser are studied as a function of temperature in a range from-30℃ to 60℃. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission within the respective intermanifold transitions of ^4F3/2→^4I9/2are investigated. The 946.0-nm line shifts toward the shorter wavelength and broadens. In addition, the threshold power and slope efficiency of the 946.0-nm laser line are quantified with temperature.The lower the temperature, the lower the threshold power is and the higher the slope efficiency of the 946.0-nm laser line is,thus the higher the laser output is. This phenomenon is attributed to the ion-phonon interaction and the thermal population in the ground state.

Cutting of nonmetallic materials using Nd:YAG laser beam

This study deals with Nd：YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd：YAG laser beam power besides work piece scanning speed. For approximate cutting depth, a theoretical study is conducted in terms of material property and cutting speed. Results show a nonlinear relation between the cutting depth and input energy. There is no significant effect of speed on cutting depth with the speed being larger than 30 mm/s. An extra energy is utilized in the deep cutting. It is inferred that as the laser power increases, cutting depth increases. The experimental outcomes are in good agreement with theoretical results. This analysis will provide a guideline for laser-based industry to select a suitable laser for cutting, scribing, trimming, engraving, and marking nonmetallic materials.

Experimental study of electro-optical-switched pulsed Nd:YAG laser

We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd：YAG laser. We ex- perimentally study and compare the performance of the pulsed Nd：YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configu- ration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.

Controlled Laser Transformation Hardening of Martensitic Stainless Steel by Pulsed Nd:YAG Laser

Laser transformation hardening （LTH） was applied to the surface of the AISI 420 martensitic stainless steel by a pulsed Nd：YAG laser to obtain optimum hardness. The influences of process parameters （laser pulse energy, duration time, and travel speed） on the depth and hardness of laser treated area were investigated. Image analysis of SEM microstructure of AISI 420 showed that plate-like carbide have almost fully and （30-40）% of globular carbide particles dissolved into the matrix after laser transformation hardening by pulsed laser and the microstructure was refined to obtain controlled tempered martensite microstructure with 450 VHN hardness.

Polarization switching in a quasi-isotropic microchip Nd:YAG laser induced by optical feedback

This paper demonstrates the influence of external optical feedback on the polarization state of longitudinal modes in quasi-isotropic microchip Nd：YAG lasers. Under optical feedback, the polarization state of longitudinal modes in quasi-isotropic lasers relies strongly on the intracavity anisotropy loss and mode competition. When the intracavity anisotropy loss is small, external optical feedback can cause polarization switching and strong mode competition between two orthogonal linearly polarized eigenstates of one laser longitudinal mode, which leads to the distortion of laser intensity modulation waveform. The polarization switching is independent of the initial external cavity length. By increasing the intracavity anisotropy loss, one polarization eigenstate can be suppressed and the laser works in single-polarization state. A theoretical analysis based on the compound cavity model is presented, which is in good agreement with the experimental results. The results offer guidance to the development of laser feedback interferometers.

Multipulse Nd:YAG Laser Thomson Scattering Diagnostics on HT-7 Tokamak

A multipulse Nd：YAG （Neodym-yttrium aluminium garnet） laser Thomson scattering diagnostic system developed was recently applied on HT-7 tokamak to obtain more accurate electron temperatures. A CAMAC-based real-time computer system for laser control, data acquisition, analysis and calibration was investigated in detail. Furthermore, the reliability and accuracy of this diagnostic system were demonstrated by comparing the results with those of a soft-X ray diagnostic system.

LD环状侧面均匀泵浦Nd∶YAG激光振荡器

激光二极管(Laser Diode,LD)环状侧面均匀泵浦的激光振荡器具有结构简单、光束质量高、单脉冲能量大等特点,常常在高能脉冲固体激光器中作为主振荡功率放大(MOPA)结构的振荡器,一直是国内外科研人员研究的重要方向之一。本论文通过Zemax软件对不同激光二极管排列方式以及不同工作物质吸收系数对吸收光场的影响的进行了仿真。基于仿真结果,设计了一种20个bar条串联的环状侧面泵浦结构,以提高晶体吸收的均匀性。通过该环状侧泵结构,结合超高斯非稳腔设计,搭建了一种双棒串接激光振荡器进行实验研究。该振荡器实现了在100 Hz重复频率下,单脉冲能量为496 mJ、脉冲宽度为12.4 ns的1064 nm激光输出,光束质量优于9 mm·mrad,光-光转换效率为18.5%。并且该振荡器可以维持光轴稳定不变的同时,实现20 ns脉宽以内变档可调。实验结果证明了该环状侧面均匀泵浦结构可靠有效,为MOPA结构振荡器选取提供了一种有效的方案。

双波长LD泵浦Nd^(3+)∶YAG免温控被动调Q激光器的研究

传统的固体激光器体积、重量大,功耗高,限制了其在空间受限设备中的应用。被动调Q的LD泵浦免温控固体激光器省去了复杂的温度控制装置,调Q机构简单,能够满足复杂温度环境的特殊应用场景的小型化、低功耗要求。提出了基于双波长LD泵浦实现宽温度范围免温控阈值自适应的1.06μm激光脉冲输出方法。基于Nd∶YAG晶体设计了角锥棱镜谐振腔,仿真分析了LD泵浦源到激光棒的面心距对热负载的影响,并确定4 mm的最佳面心距。数值分析了相同泵浦功率下-40~60℃温度范围内激光静态能量输出变化,以及不同初始透过率的可饱和吸收体对激光阈值脉宽的影响。计算结果表明在-37℃~60℃范围内,阈值脉宽都在200μs以下,阈值脉宽最低点达到了29.4μs。构建主波实时探测的阈值自适应调节装置并搭建实验系统,实验结果表明,在温度范围为-35~60℃时,阈值脉宽变化范围为40~180μs。采用激光腔体一体加工成型,应用轻量化的铝合金材料,实现工程化应用,体积83.5 mm×44 mm×29.5 mm,重量约为230 g。在23.8%初始透过率的饱和吸收体条件下实现单脉冲输出能量42 mJ,脉冲宽度5.2 ns。

低通量Q开关Nd∶YAG激光联合微针导入氨甲环酸治疗黄褐斑

目的评估低通量Q开关Nd∶YAG(QSNY)激光单一治疗与其联合微针导入氨甲环酸治疗黄褐斑的疗效差别,并基于皮肤镜分型分析不同类型黄褐斑的最佳治疗方式。方法收集2022年1月—2023年12月就诊的黄褐斑患者的临床资料,比较QSNY激光单一治疗组(对照组,23例)与QSNY激光联合微针导入氨甲环酸治疗组(联合组,23例)治疗3次后改良黄褐斑面积和严重程度指数(mMASI)评分、皮肤镜检查总评分(TDS)、医生临床评估(PGA)和不良反应的发生率。结果2组患者治疗后mMASI评分均降低,联合组的mMASI评分改善优于对照组(P<0.05);2组患者治疗后TDS均降低,联合组改善程度更佳,差别有统计学意义(P<0.05)。与治疗前比较,联合组治疗后毛细血管扩张明显改善,差别有统计学意义(P<0.001)。2组患者的PGA评分比较,差别无统计学意义(P>0.05)。2组患者治疗后均未发现明显的不良反应。结论QSNY激光联合微针导入氨甲环酸治疗黄褐斑的疗效优于单一激光治疗,前者对血管增生和表皮色素沉着明显的黄褐斑更有利。

激光虹膜成形术联合Nd∶YAG激光治疗闭角型青光眼疗效及对术后视力水平、房角结构变化的影响

目的探究激光虹膜成形术(ALPI)联合Nd∶YAG激光应用于闭角型青光眼(ACG)的疗效及对术后视力水平、房角结构变化的潜在影响。方法回顾性分析以宝鸡市人民医院2020年7月至2023年7月收治的114例(168眼,含60例单眼患病与54例双眼患病)ACG患者为研究对象。将2020年7月至2021年7月的52例(80眼)纳入对照组,2021年7月至2023年7月的53例(88眼)纳入观察组。其中,对照组接受前房穿刺术联合Nd∶YAG激光治疗,观察组接受ALPI联合Nd∶YAG激光治疗。比较两组患者术前和术后12个月的房角结构及房水系统功能指标变化和角膜内皮细胞参数变化。于术前、术后1个月、术后4个月和术后12个月比较眼压状态和最佳矫正视力水平,并记录并发症发生情况。结果两组患者在术后1、4、12个月眼压较术前均降低,且观察组较对照组更低(P均<0.05);最佳矫正视力水平较术前均升高,且观察组较对照组更高(P均<0.05)。术后12个月,两组前房深度、前房角度、Schlemm管直径和小梁网面积较术前均升高,且观察组较对照组升高幅度更大(P均<0.05);细胞密度(CD)、最小细胞面积(MIN)、最大细胞面积(MAX),平均细胞面积(AVE)、细胞面积标准差(SD)和变异系数(CV)较术前均降低,但除CD外,观察组比对照组更高(P均<0.05)。结论ALPI联合Nd∶YAG激光治疗能显著控制ACG患者眼压,使最佳矫正视力水平及房角结构及功能改善明显,可减轻角膜内皮细胞损伤程度。