微脉冲半导体激光照射对正常大鼠视网膜损伤的观察

目的观察810 nm微脉冲半导体激光照射对正常棕色挪威大鼠（BN 大鼠）视网膜的损伤。方法使用不同能量及负载系数（duty cycle, D C）的810 nm微脉冲半导体激光对130只BN大鼠眼进行照射。分别于激光照射后第1、3、7、1 4、28 d进行彩色眼底照相、荧光素眼底血管造影及组织病理学观察，并检测热休克蛋白(HSP-70)在视网膜的表达情况，用TdT介导dUTP缺口末端标记法(TUNEL)检查细胞凋亡 。结果阈值及阈上能量条件下，低DC时激光照射部位无光学显微镜下的组织病理学改变，高DC时出现可累及视网膜内核层组织的严重损伤；微脉冲半导体激光照 射后1 d大鼠视网膜内核层细胞HSP-70阳性表达细胞即较正常视网膜明显增加，3 d时达到高峰，以后逐渐下降，14 d时恢复近正常水平。HSP-70阳性细胞数量 随激光能量提高而增加。TUNEL染色可见激光照射部位凋亡细胞主要存在于视网膜色素上皮（RPE）层、外核层、内核层，甚至脉络膜层，其数量随激光能量增高而增多。在激光照射后第3 d，凋亡细胞数量最多。结论810 nm微脉冲半导体激光照射后，视网膜损伤程度与激光能量及DC呈正相关。低能量高负载系数（50 mW，50％）或高能量低负载系数（100 mW，5％～15％）时，损伤限于RPE层，避免了神经上皮层的损伤。激光照射后HSP-70高表达及细胞凋亡可能在组织损伤修复过程发挥重要作用。（中华眼底病杂志，2008，24：122-126）

Experimental Studies of Micropulse Diode Laser Treatment of Normal Retina in BN Rats

Objective To investigate the effect of micropulse diode laser treatment on the retina in Brown-Norway rats(BN Rats). Methods 130 eyes of BN rats received irradiance of different powers of micropulse diode laser with 810-nm wave-length through a contact lens.Fundus color photography and fundus fluorescein angiography(FFA)were performed on day 1,3,7,14 and 28 days after treatment.Animals were sacrificed on 1,3,7,14 and 28 days separately for historical study.The expression of heat shock protein-70(HSP-70)in the retina was observed with immunohistochemistry.Cell apoptosis of retina tissue was examined bv TdT mediated dUTP nick end labeling(TUNEL). Results (1)No change was found in no visible reaction laser spots by light microscope.High duty cycles with threshold and suprathreshold energies can produce severe damage even to the inner nuclear layer.(2)HSP-70expression was markedly increased in the inner nuclear layer at 1d after micropulse diode laser.This increase in HSP-70 expression peaked at day 3 whereafter a decline near to normal at 2 weeks was detected.(3)Apoptosis was detected mainly in retinal pigment epithelium,outer nuclear layer,inner nuclear layer and even choroid bv TUNEL after micropulse diode laser treatment.The TUNEL-positive cells increased with the laser power.Maximum TUNEL-positive cells could be seen at day 3 after treatment. Conclusions The retinal injury has positive relationship with laser energy.The thermal damage is confined to the RPE and spare the neurosensory retina when using threshold power(50mW)with 50%duty-cycle and supra-threshold power with high duty-cycle(100mW,5%～15%).The hyper expression of HSP-70 and apoptosis mechanism may play an important role in the tissue repair process.