阈值下微脉冲激光光凝治疗糖尿病性黄斑水肿的作用机制及临床应用

Subthreshold micropulse laser photocoagulation for diabetic macular edema

阈值下微脉冲激光光凝(subthreshold micropulse laser photocoagulation,SMLP)是在传统激光技术上的改良,可将连续波激光束切割成一系列重复的微秒级脉冲,使组织在各脉冲之间冷却,从而减少了热量的累积,为糖尿病性黄斑水肿(diabetic macular edema,DME)的治疗提供了一种新的选择。SMLP的作用靶点位于视网膜色素上皮(retinal pigment epithelial,RPE)层,可刺激诱导RPE细胞泵功能的恢复,促进视网膜下和视网膜内水肿的快速吸收。目前,此种低能量、高密度激光光凝模式单独或与其他疗法联合应用于DME患者,达到了较佳的视力预后及水肿消退效果,对视网膜神经感觉层及脉络膜层无热损伤,且多次重复治疗可增加治疗效果但无累积损伤,有望成为治疗DME以及其他视网膜血管性疾病并发黄斑水肿的一线选择。

Sub-threshold micropulse laser photocoagulation( SMLP) is an alternative to the conventional continuous-wave laser for the treatment of diabetic macular edema ( DME) . In contrast to the conventional laser, the therapeutic effect of the SMLP is not accompanied by thermal retinal damage. In SMLP, a train of repetitive short laser pulses delivers the laser energy within an "envelope", which was described as"duty cycle". Each"envelope" includes"ON" time, which is the duration of each micropulse, and"OFF"time, which is the time between the micropulses. The "OFF" time is important since here the originated heat can cool down. This leads to the required activation of the RPE cells, promotes rapid absorption of subretinal and intraretinal edema, but the thermal wave will only reach the neural retina at temperatures beneath the protein denaturation threshold. As a low-energy, high-density laser photocoagulation mode, SMLP is expected to be the first choice for the treatment of DME. It has been proved that SMLP alone or in combination with other therapies, achieved better visual outcome and edema regression, without any thermal damage to the retinal neurosensory layer and choroid. In this article we will review the mechanism, development history and applications of SMLP for DME.