微脉冲半导体激光的临床应用现状

微脉冲半导体激光是一种阈下光凝技术 ,它能选择性地作用于视网膜色素上皮细胞 ,避免损伤视网膜神经层 ,在产生治疗作用的同时最大限度地保持视功能 ,对治疗黄斑水肿、中心性浆液性脉络膜视网膜病变 (中浆 )和玻璃膜疣具有较好的疗效。本研究阐述了微脉冲半导体激光的原理、临床应用及激光光凝斑检测等方面的进展。     

微脉冲激光技术在眼科的应用

眼底激光是眼底病治疗的一项重要武器，其应用甚广，但激光本身所造成的组织损伤却是一个令眼科医生困扰的问题，长期以来如何使治疗效果达到最佳，而组织损伤降低到最小，一直是激光治疗所追求的目标。为了取得最优化的激光治疗效果，人们在激光的波长、波形、脉冲频率等方面作了很多尝试，微脉冲激光就是由此产生的新技术。     

半导体激光在眼科的应用进展

半导体激光穿透力强，主要作用于视网膜深层和脉络膜层。组织吸收能量后，因光热效应而发生凝固、汽化、切割等效应，目前临床上主要用于青光眼、视网膜脉络膜等疾病的治疗，尤其对顽固性青光眼、脉络膜黑色素瘤和脉络膜新生血管更具优越性。     

微脉冲阈值下半导体激光在视网膜疾病中的应用研究进展

激光光凝治疗已经在多种视网膜疾病治疗中取得了满意的效果,已成为眼底疾病治疗的重要手段之一。微脉冲阈值下半导体激光（subthreshold diode micropulse laser,SDM）是近年来激光治疗中研究较热门的一种,目前SDM在多种视网膜疾病引起的黄斑水肿的治疗中取得了较满意的疗效,且有效降低了并发症的发生。本文就SDM的概念、治疗原理以及其对视网膜组织产生的影响进行总结,并就其在多种视网膜疾病治疗中的应用进展进行综述。     

微脉冲半导体激光对兔视网膜损伤的实验研究

目的初步研究微脉冲半导体激光对兔眼视网膜损伤的生物学效应。方法8只有色兔(16眼)中每只眼的上、下方视网膜随机分别行810nm半导体激光连续波阈值光凝及微脉冲阈下光凝,于光凝后即刻观察光斑反应和眼底荧光造影后荧光素渗漏情况,并在光镜和电镜下观察其对视网膜和脉络膜造成的组织学改变。结果微脉冲激光阈下光凝后光斑不可见,亦无荧光素渗漏,视网膜损伤不明显;阈值光凝后可见光斑反应并有荧光素渗漏,视网膜损伤明显,外核层细胞数量减少,内、外核层均出现少量核固缩和胞浆空泡化,视网膜色素上皮细胞增生,Bruch膜完整无损。结论微脉冲激光光凝视网膜不会损伤视网膜,但确定阈能量时要从低能量起,且选择周边视网膜。     

微脉冲半导体激光治疗CSC的初步观察

目的:探讨微脉冲半导体激光治疗中心性浆液性脉络膜视网膜病变(central serous chorioretinopathy,CSC)的疗效。方法:自身对照病例研究。将经荧光素眼底血管造影(fundus fluorescein angiography,FFA)和光学相干断层扫描(optic coherence tomography,OCT)检查确诊的典型性CSC患者12例12眼行微脉冲半导体激光治疗前及治疗后随访观察1,2wk;1,3mo的临床资料进行分析,主要以治疗前后的视力、自觉症状、眼底情况、FFA及OCT检查的改变为观察指标,以评价微脉冲半导体激光对CSC的治疗效果。结果:所有患者自觉症状减轻或消退,视力及视觉质量均有不同程度改善。激光光凝2wk和1mo后,分别有9眼(75.0%)和11眼(91.7%)的黄斑区水肿完全消退,3mo后全部患者黄斑区水肿消退。光凝2wk后,FFA检查发现有9眼荧光素渗漏完全消失,3眼渗漏减轻;OCT检查有9眼黄斑区视网膜下积液消失,中心凹视网膜厚度恢复正常,3眼黄斑区视网膜下积液大部分吸收。光凝1mo后,FFA检查有11眼荧光素渗漏完全消失;OCT检查有11眼黄斑区视网膜下积液消失,中心凹视网膜厚度恢复正常。光凝3mo后,FFA显示所有患眼的荧光素渗漏完全消失,未见明显"窗样缺损"样荧光;OCT检查发现所有患眼黄斑区视网膜下积液完全吸收。结论:微脉冲半导体激光治疗CSC是一种安全、有效的治疗方法,能有效缩短病程,提高患者视力,避免并发症的发生。     

微脉冲半导体激光与氩激光对兔视网膜损伤及修复的组织学研究

目的观察微脉冲半导体激光与氩激光对兔视网膜损伤和修复的组织学反应。方法在黄斑水肿治疗参数下分别对兔眼行微脉冲阈下光凝和氩激光光凝,观察视网膜组织学改变。结果微脉冲阈下光斑不可见而氩激光可见;激光后两者光镜下视网膜感光细胞损伤不明显但脉络膜小静脉轻度充血,4周后消退;电镜下氩激光光斑处外节排列稀疏,色素上皮细胞（RPE）和节细胞肿胀,外核层细胞异染色质增多,4周后RPE和胶原增生明显,脉络膜内色素颗粒增生;而微脉冲光斑变化不明显。结论微脉冲激光光凝视网膜较氩激光损伤更轻微。     

半导体激光在眼科的应用

半导体激光的波长属红外光，能量可被眼组织高度吸收，穿透力强，因热效应使局部组织反应程度不同而有热凝固，汽化，穿孔和切割等一系列反应。临床研究证实：半导体激光不仅可用于各种青光眼手术，还可应用于玻璃体视网膜和脉络膜疾病的治疗。在治疗脉络膜黑色素瘤，黄斑中心凹脉络膜新生血管更具有优越性。半导体激光因其能量输出稳定，效率高，体积小，结构简单，不需外循环冷却水等特点，为激光在眼科的应用开拓了新领域。     

微脉冲半导体激光对兔眼视网膜损伤的形态学观察

目的:研究微脉冲半导体激光对兔眼视网膜损伤的生物学效应.方法:有色兔8只16眼,每眼上、下方视网膜随机分别行810nm半导体激光连续波阈值光凝及微脉冲阈下光凝,于光凝后即刻观察光斑反应和眼底荧光造影后荧光素渗漏情况,并在光镜和电镜下观察其对视网膜和脉络膜造成的组织学改变.结果:微脉冲激光阈下光凝后光斑不可见,亦无荧光素渗漏,视网膜损伤不明显;阈值光凝后可见光斑反应并有荧光素渗漏,视网膜损伤明显,外核层细胞数量减少,内、外核层均出现少量核固缩和胞质空泡化,视网膜色素上皮细胞增生,Bruch膜完整无损.结论:微脉冲激光光凝视网膜不会损伤视网膜,但确定阈能量时要从低能量起,且选择周边视网膜.     

微脉冲半导体激光与氩激光对兔视网膜损伤的形态学比较

目的:研究微脉冲半导体激光和氩激光对兔眼视网膜损伤的形态学改变。方法:有色兔8只16眼,每只兔的两眼随机分别行810nm微脉冲阈下光凝和514nm氩绿激光光凝,在黄斑水肿治疗参数下,光凝后即刻观察光斑反应并在光镜和电镜下观察其对视网膜和脉络膜造成的组织学改变。结果:微脉冲激光阈下光凝后光斑不可见,氩激光光凝后可见光斑反应;激光后即刻两者光镜下视网膜感光细胞损伤不明显但脉络膜毛细血管、小静脉轻度充血,电镜下氩激光光凝处外节排列稀疏,色素上皮细胞和节细胞肿胀,外颗粒层细胞异染色质增多。微脉冲光凝处外节排列较整齐,外颗粒层变化不明显。结论:微脉冲激光光凝视网膜较氩激光损伤更轻微。     

Micropulse diode laser photocoagulation for central serous chorio-retinopathy

Purpose:  Central serous chorioretinopathy (CSC) is usually characterized by a localized detachment of the neurosensory retina that is self-limiting. However, some cases may persist or recur leading to degenerative changes of the retinal pigment epithelium and the neurosensory retina resulting in severe visual loss and requiring intervention.
Methods:  This retrospective case series reports the long-term visual outcome of the use of micropulse laser photocoagulation for this condition with a review of literature.
Results:  The mean follow up was 17.1 months. Four of the five patients had complete resolution of symptoms whereas one patient had recurrent CSC from a new leak that failed to resolve after repeat micropulse treatment despite improvement in symptoms.
Discussion:  The outcomes in this case series confirm the long-term efficacy of micropulse laser in the management of CSC. It produces therapeutic effects that appear comparable to those of conventional photocoagulation with no detectable signs of laser-induced iatrogenic damage.     

Micropulse transscleral diode laser cyclophotocoagulation in the treatment of refractory glaucoma

Background: Transscleral diode laser cyclophotocoagulation (TSCPC) is an established method of treatment for refractory glaucoma, but is associated with significant complications. This study evaluates the efficacy and safety of a new form of TSCPC using micropulse diode laser and trans‐pars plana treatment with a novel contact probe. Methods: Prospective interventional case series of 40 eyes of 38 consecutive patients with refractory glaucoma treated with micropulse TSCPC with a novel probe. Outcomes measured were success, hypotony and response rates. Results: The mean age of patients was 63.2 ± 16.0 years. The mean follow‐up period was 16.3 ± 4.5 months. The mean intraocular pressure (IOP) before micropulse TSCPC was 39.3 ± 12.6 mmHg. Mean IOP decreased to 31.1 ± 13.4 mmHg at 1 day, 28.0 ± 12.0 mmHg at 1 week, 27.4 ± 12.7 mmHg at 1 month, 27.1 ± 13.6 mmHg at 3 months, 25.8 ± 14.5 mmHg at 6 months, 26.6 ± 14.7 mmHg at 12 months and 26.2 ± 14.3 mmHg at 18 months (P < 0.001 at all time points). No patient had hypotony or loss of best‐corrected visual acuity. The overall success rate after a mean of 1.3 treatment sessions was 72.7%. Conclusion: Micropulse TSCPC is a safe and effective method of lowering IOP in cases of refractory glaucoma and is comparable with conventional TSCPC.     

Micropulse diode laser trabeculoplasty – 180‐degree treatment

Purpose: To evaluate the outcome of 180° micropulse diode laser trabeculoplasty (MDLT) in patients with open‐angle glaucoma. Methods: A retrospective review of 40 eyes of 29 MDLT‐treated patients with a minimum follow‐up time of 6 months. Successful outcome was defined as follows: (i) a ≥20% or (ii) a ≥3‐mmHg decrease of intraocular pressure (IOP), no further need for laser‐ or incisional surgery and the number of glaucoma medication was the same or less than preoperative. These definitions will from now on be referred to as definition one and definition two. Results: Life‐table analysis showed an overall success rate of 2.5% (1/40) and 7.5% (3/40) (according to definitions one and two, respectively) after up to 19 months of follow‐up. The average time for failure was by definition one 2.9 months (standard deviation, SD ± 3.5, range 1–12 months) and by definition two 3.3 months (SD ± 3.9, range 1–16 months). There were no intra‐ or postoperative complications caused by MDLT. Postoperative inflammatory reaction, cells and flare, was scanty. Conclusion: Our results suggest that 180° MDLT is a safe but ineffective treatment in patients with open‐angle glaucoma.     

Micropulse laser in the treatment of diabetic macular edema

The micropulse laser is a new development in laser therapy. Micropulsing is frequent short pulses of subthreshold intensity applied to retinal lesions. It has been shown to be effective in diabetic macular edema, branch vein occlusion, and drusen. Although the initial landmark studies showed it to be effective, the exact parameters have not been established. This article illustrates the current state of its use.     

Micropulse and continuous wave diode retinal photocoagulation: visible and subvisible lesion parameters

BACKGROUND/AIM: Subvisible micropulse diode laser photocoagulation localises retinal laser damage because brief micropulses allow little time for heat conduction to spread temperature rise from the retinal pigment epithelium to the neural retina. Treatment power is often chosen as a multiple of that needed for visible continuous wave lesions. The authors measured clinical laser powers needed for visible end point micropulse and continuous wave diode laser retinal photocoagulation. METHODS: Six parallel rows of 10 diode laser (810 nm) burns were made in the superior peripheral retina of six consecutive patients undergoing their initial frequency doubled Nd:YAG (532 nm) panretinal photocoagulation for proliferative or severe non-proliferative diabetic retinopathy. All photocoagulation exposures were 125 microm in retinal diameter and 0.2 seconds in duration. Micropulse exposures were performed with 500 Hz, 0.3 ms micropulses. The minimal power needed (1) for visible continuous wave diode photocoagulation was determined from two adjacent rows of laser lesions and (2) for visible micropulse diode photocoagulation from four additional adjacent rows of laser lesions. Fluorescein angiograms and red-free fundus photographs were obtained immediately and 6 days after laser photocoagulation in each patient. Calculations were performed to determine the extent to which clinical parameters exceeded ANSI Z136.1-2000 maximal permissible exposure (MPE) levels for laser exposure. RESULTS: Continuous wave and micropulse lesions typically required 300 mW (60 mJ) and 1800 mW (54 mJ), respectively. Visible continuous wave and micropulse lesions exceeded MPE levels by multiples of 36 x and 133 x, respectively. Laser energies were similar for visible continuous wave and micropulse lesions. CONCLUSION: Visible micropulse lesions require 6 x more power but roughly the same energy as visible continuous wave lesions. No significant difference was demonstrable in the minimal power needed for photographically and angiographically apparent diode micropulse lesions. MPE levels are designed to provide a 10 x safety margin. This safety margin was 3.7 x greater for micropulse than continuous wave diode laser photocoagulation.     

Micropulse laser for the treatment of glaucoma: A literature review

Glaucoma, a progressive optic neuropathy, is the leading cause of irreversible blindness worldwide. Glaucoma patients are usually initially managed with medications and laser therapies, before more invasive ocular surgeries. For laser treatments of glaucoma, laser trabeculoplasty and laser transscleral cyclophotocoagulation lower the intraocular pressure by increasing the aqueous outflow and decreasing the aqueous production, respectively. The development of a subthreshold laser technique, the micropulse laser, has been investigated as a potential alternative to traditional glaucoma laser procedures, with an aim to further decrease the risk of side effects without compromising the laser treatments' efficacy. Few reviews have been done on the 2 current micropulse laser treatments for glaucoma—micropulse laser trabeculoplasty and micropulse transscleral cyclophotocoagulation. Hence, the purpose of this review was to assess the efficacy and safety of micropulse laser techniques in the treatment of glaucoma.