脉冲1.338μm激光致青紫蓝灰兔视网膜损伤效应研究

Retinal injury of chinchilla grey rabbit induced by pulsed 1.338 μm laser

目的研究脉冲1.338μm激光致青紫蓝灰兔视网膜损伤效应,确定其损伤阈值。方法以输出波长1.338μm、脉冲宽度5 ms的移频Nd∶YAG激光为照射光源,角膜入射光斑直径5 mm,在19.8、24.2、29.5和33.9J/cm24个剂量下照射12只青紫蓝灰兔的24只眼视网膜,于照后即刻、1 h、24 h和48 h用检眼镜观察视网膜损伤,统计各个剂量下的损伤发生率,采用加权概率单位法计算损伤发生率为50%时所对应的激光剂量,即损伤阈值ED50。于照后48 h摘取眼球进行视网膜病理观察。结果阈值水平的视网膜损伤为淡淡的灰白色凝固斑,边界模糊,较重者损伤斑为白色,有的伴有点状或环形出血。视网膜损伤发生率随照射剂量的升高而升高,随时间的延长在照后24 h内略有升高,到照后48 h不再上升。统计分析照后1 h、24 h的损伤发生率确定视网膜损伤阈值分别为4.83 J/cm2(95%置信区间4.60～5.05 J/cm2)和4.60 J/cm2(95%置信区间4.31～4.86 J/cm2)。光镜下观察视网膜损伤区向内隆起,内、外核层、节细胞层等各层细胞都可观察到胞核固缩、深染等损伤特征,但色素上皮层细胞形态未发生明显改变。结论脉冲1.338μm激光在角膜入射光斑直径5 mm,脉冲宽度5 ms条件下致青紫蓝灰兔视网膜损伤的阈值为4.60 J/cm2。视网膜损伤累及视网膜全层,但色素上皮层损伤较轻。

To study the retinal injury effects of chinchilla grey rabbit induced by pulsed 1. 338 μm laser radiation and establish the retinal damage threshold （ ED50 ）. Methods A neodymium： yttrium aluminum garnet （ Nd： YAG） laser was used to deliver 1. 338 μm laser to the retinas of 12 chinchilla grey rabbits. The pulse duration was 5 ms. The laser spot diameter on cornea was 5mm. The incident laser dose was 19.8,24.2,29.5 and 33.9 J/cm^2. The exposed sites were clini-cally evaluated with direct ophthalmoscope for the presence or absence of lesions at 0 h, 1 h,24 h and 48 h post-exposure. The ED50was calculated with probit analysis method. Retinas were collected at the 48 h endpoint and prepared for micro- scopic evaluation. Results Retinal injuries seen under ophthalmoscopy were faint white-grey spots at threshold and white spots at higher dose, some of which were accompanied with sub-retinal hemorrhage. The percentage of injured spots increased with the applied laser dose and the time-delay of observation within 24 h. The retinal ED50 was determined to be 4.83 J/em2 （95~ confidence interval 4.60- 5.05 J/cm^2） and at 1 h and 4.60 J/cm^2 （95% confidence interval 4.31 - 4.86 J/cm^2 ） at 24 h checkpoint. Histological section showed a full thickness retinal lesion, including the inner and outer nucleus layer and the ganglion layer, though the retinal pigmented epithelium （RPE） showed no obvious change. Conclu-sion The established EDs0 of rabbit retina for pulsed 1. 338 μm laser is 4.60 J/cm^2. A characteristic full thickness retinal lesion can be induced by laser exposure even at threshold level, though only limited lesion happened to the RPE.