紫外线照射对大鼠泪膜稳定性和角膜组织的影响

Effect of ultraviolet irradiation on the stability of tear film and corneal tissue of rats

目的探究不同强度和时间紫外线照射对大鼠泪膜稳定性和角膜组织的影响。设计实验研究。研究对象50只健康SD大鼠(6周,200~250 g)。方法将大鼠随机分成5组(空白对照组N和实验组A、B、C、D),每组10只,A、C组紫外线照射强度为142μw/cm^2,每次照射时长为8、12分钟;B、D紫外线照射强度为94μw/cm^2,每次照射时长为12、18分钟。共照射42天,每周照射3次,均间隔1天,照射后第14、28、42天,裂隙灯检查、荧光素染色及泪膜破裂时间(BUT)测定、Schirmer I试验(SIt)。49天时注射过量水合氯醛处死大鼠,制作角膜组织切片。主要指标结膜、角膜、泪膜形态结构变化,角膜荧光素染色评分,BUT,SIt值,角膜组织切片观察。结果裂隙灯检查显示B、C组对比,照射强度较高组比较低组睑结膜充血、角膜水肿、角膜混浊出现早且严重,较高强度组照射后出现角膜新生血管,较低强度组以泪液质和量改变为主要特征。A、C组对比,长时间照射组比短时间照射组角膜水肿、混浊和新生血管出现的时间早且严重,且长时间照射组睑裂区出现条状溃疡。荧光素染色显示,正常组染色评价结果为阴性,A组为阳性,B组为弱阳性,C、D组为强阳性。第42天,A、B、C、D组BUT值分别较对照组明显减少(P均<0.01)。第42天,实验组SIt值分别较对照组均明显增加(P均<0.01)。组织学观察显示,较高强度紫外线照射引起角膜新生血管,内皮细胞密度下降,基质层纤维细胞排列紊乱。较低强度短时间照射引起上皮层增厚。较低强度长时间照射引起角膜新生血管,基质层纤维细胞排列紊乱。结论长时间紫外线照射可引起睑结膜充血、角膜上皮损伤、泪液质和量改变等眼表结构变化,这些变化随照射强度增大或照射时间增长而出现更早、程度更重。

Objective To investigate the impact of different ultraviolet（UV） irradiated intensity and duration on the stability of tear film and corneal tissue of rats. Design Experimental study. Participants 50 male SD rats. Methods Fifty healthy male SD rats were randomly divided into the normal control group, test group A, B, C, D. Tested rats received UV irradiation three times a week for 6 weeks. Each irradiation had one-day interval. Every time,the rats in the test group A and C were exposed to the UV of 142 μw/cm^2 for 8 min, and 12 min respectively. The rats in the test group B and D were exposed to the UV of 94 μw/cm^2 for 12 min, and 18 min respectively. The results of examination at 14 d, 28 d, 42 d after exposure to UV irradiation were recorded. The examinations include slit lamp observation and photograph, sodium fluorescein dye; tear film break-up time （BUT） and basal tear secretion（Schirmer’s-I test, SIt）. The rats were sacrificed by overdose of chloral hydrate and the corneal tissue sections were made. Main Outcome Measures Changes of morphological structure of conjunctiva, cornea and the tear film, corneal fluorescein staining scores, BUT, basic tear secretion, corneal tissue section observation. Results On slit lamp observation, higher-intensity group showed a earlier and severer conjunctiva congestion, corneal edema, and corneal opacity. Higher-intensity group appeared characteristic corneal neovascularization, while low-intensity group was characterized by the changes of the quality and quantity of tear-film. Comparison of Group A and C showed that longer-irradiation-duration group had a similar tendency with higher-intensity group, moreover, it appeared characteristic stripped ulcer in palpebral area. Fluorescein staining test showed the result of the control group was negative, group A was positive, group B was weakly positive, and group C and D was strongly positive. BUT at 42th day of group A, B, C, D were significantly lower than the control group （all P〈0.01）. SIt in 42th days of group A, B, C, D were significantly higher than the control group （all P〈0.01）. Tissue sections showed that higher-intensity group （group A and group C） appeared corneal neovascularization, reduced density of endothelial cell, disordered stroma fibroblasts. While lower-intensity group with shorter irradiation-time（group B） showed thickened epithelium, and lower-intensity group with longer irradiation-time （group C） showed corneal neovascularization and disordered stroma fibroblasts. Conclusions Ultraviolet irradiation can cause ocular surface damage, which contains conjunctival congestion, corneal epithelium damage, the changes of tear-film quality and quantity. These occurred earlier and severer with increasing irradiation intensity or increasing duration of irradiation.