视网膜对铁的敏感性与抗坏血酸分布的相关性研究

目的 观察大鼠和家兔视网膜组织中抗坏血酸的分布形式与铁异物对2种不同动物的视网膜损伤形态,验证大鼠视网膜光感受器细胞对铁异物的敏感性是否与视网膜中抗坏血酸的分布有关。 方法 将5 mg铁异物分别置入32只健康雄性Sprague-Dawley (SD ) 大鼠、15 mg铁异物分别置入9只健康雄性新西兰白色家兔玻璃体腔后，苏木精-伊红（hematoxylin-eosin, HE）染色观察2种不同种动物视网膜的受损情况。凋亡原位染色（TdT-mediated dUTP-biotin nick-end labeling, TUNEL）方法观察家兔视网膜神经元的细胞凋亡。Chinoy 法染色观察抗坏血酸在2种不同的正常动物视网膜组织中的分布形式。 结果 SD大鼠铁异物置入术后，HE染色的切片仅见光感受器细胞层的破坏。新西兰白色家兔铁异物置入术后3 d，HE 染色见全层视网膜神经元细胞受损，在神经节细胞层、内颗粒层以及外颗粒层均观察到TUNEL阳性细胞核。正常SD大鼠抗坏血酸阳性染色仅见于外颗粒层；新西兰家兔视网膜全层抗坏血酸染色阳性。 结论 视网膜对铁异物毒性的敏感性与视网膜组织中的抗坏血酸分布形式有关。 （中华眼底病杂志，2003，19：269-332）     

RCS大鼠视网膜内核层变性的超微结构研究

目的　证实RCS大鼠视网膜内核层存在神经原变性。方法　利用光学显微镜和透射电子显微镜观察出生后第 18、2 0、2 8、3 5、42、45、5 6、60、70和 10 0d的RCS大鼠视网膜和正常SD大鼠视网膜组织结构的变化。并用TUNEL方法证实视网膜神经细胞存在凋亡。结果　和正常SD大鼠视网膜比较 ,RCS大鼠 18～ 2 0d开始视网膜变性 ,光感受器细胞死亡 ,内核层细胞也有不同程度的变性。RCS大鼠在出生后 2 5d ,视网膜外核层细胞核TUNEL呈阳性 ,出生后 3 5～ 45d呈强阳性 ,视网膜内核层细胞核TUNEL标记呈阳性。结论　RCS大鼠视网膜内核层细胞存在神经原变性 ,视网膜内核层细胞死亡存在凋亡这一方式。跨神经原变性很可能是这些细胞变性的机制。RCS大鼠视网膜外核层细胞存在神经原变性 ,其死亡以凋亡为主     

中药黄斑颗粒灌胃对大鼠视网膜光损伤细胞凋亡的影响

目的:观察中药复方黄斑颗粒对大鼠视网膜光损伤细胞凋亡的影响。方法:雄性SD大鼠21只分为给药组、对照组和正常组,光损伤前10d用中药复方黄斑颗粒灌胃,对照组用等体积蒸馏水灌胃,正常对照组正常饲养。光损伤白色荧光灯平均光照强度2800Lux,暗适应24h后,散瞳光照5h后置暗环境饲养,光损伤后继续给药给水,3d后取眼球做石蜡包埋切片,用TUNEL方法进行染色,同时留取眼球进行电镜观察超微形态改变。结果:正常组视网膜结构规整,几乎无TUNEL染色阳性细胞,对照组外核层有大量黄色阳性细胞,结构紊乱,给药组散在少量阳性细胞;电镜下观察可见对照组色素上皮细胞微绒毛消失,光感受器外段排列紊乱,外核层有较多的固缩凋亡细胞核,而给药组则散在少量凋亡细胞。结论:中药黄斑颗粒可能通过对抗细胞凋亡而对大鼠视网膜光损伤起到保护作用。     

大鼠实验性视网膜光损伤中的视细胞凋亡

目的 进一步探讨视网膜光损伤的发病机制。 方法 20只Wistar大鼠分为实验组、对照组,分别在光照后12,24,36小时摘除眼球,视网膜组织行HE染色和核苷酸末端转移酶介导的DUTP缺口翻译法(TdT-mediated dUTP nick end labelling method,TUNEL)标记凋亡细胞。 结果 光照后12小时,视杆细胞外节出现少量空泡变性;24小时后,外核层出现明显的细胞核破碎、浓染和DNA裂解;36小时后,视杆细胞内、外节溶解,外核层大量细胞核丢失。 结论 视细胞凋亡是大鼠实验性视网膜光损伤的重要机制之一。 (中华眼底病杂志, 1999, 15: 167-169)     

眼铁质沉着症临床分析

目的 探讨眼铁质沉着症的临床表现和发病机制。方法 对因眼内异物引起的10例（10眼）眼铁质沉着症进行X线眼内异物定位检查，2例采用巩膜外磁性试验后牵引至睫状体平坦部吸出；2例晶状体异物行白内障囊外摘出合并后房型人工晶状体植入；6例行平坦部三通道闭合式玻璃体手术摘出异物，其中2例视网膜脱离行视网膜复位手术并注入硅油。结果 2例晶状体异物的术后视力恢复到0．5和0．6；其余8例视力未见明显提高。2例玻璃体视网膜手术，分别于术后6、9月取出硅油，视网膜复位。结论 眼内铁质异物存留所致的眼铁质沉着症后果严重，造成视功能的严重障碍，且异物摘出较困难，术后视力改善不理想。因此在临床上对有异物伤病史的患者，一定要排除眼内异物的存在，一旦发现眼内铁质异物，应尽快摘出，避免铁质沉着症的发生。     

缺血再灌注损伤诱导大鼠视网膜细胞凋亡

目的 观察缺血再灌注大鼠视网膜损伤及细胞凋亡情况。 方法 采用升高大鼠眼压到109.725 mm Hg(1 mm Hg=0.133 kPa)持续1 h的方法制作视网膜缺血再灌注模型，采用常规眼球切片观察不同缺血和再灌注时间的视网膜损伤的组织病理改变；采用DNA琼脂糖凝胶电泳法检测视网膜神经元凋亡情况；采用DNA原位末端标记(terminal dUTP nick end labelling, TUNEL)法定位凋亡的视网膜细胞。 结果 缺血30 min 再灌注24、48 h的大鼠视网膜无明显的病理改变；缺血60 min再灌注24、48 h的大鼠视网膜神经节细胞层和内核层细胞明显变薄；缺血60 min再灌注12、24 h的大鼠视网膜有梯状条带。而正常对照组、缺血30 min再灌注24、48 h组及缺血60 min再灌注48 h组大鼠视网膜均无类似表现。TUNEL法显示视网膜内的细胞凋亡主要发生在节细胞和内核层光感受细胞。 结论 大鼠视网膜缺血再灌注主要是导致视网膜神经节细胞层和内核层细胞损伤，细胞凋亡可能是损伤的重要机制。 (中华眼底病杂志, 2002, 18: 296-298)     

Rhodopsin和recoverin在MNU诱导的光感受器损伤中的表达变化

目的：观察N-甲基-N-亚硝基脲( MNU)诱导的大鼠视网膜光感受器损伤过程中Rhodopsin 和recoverin表达变化与损伤的时效关系。
　　方法：将36只SPF级7周龄大鼠随机分为正常对照组, MNU模型组(6h组,12h组,24h组,3d组,7d组),每组各6只。模型组一次性腹腔注射60mg/kg MNU,正常对照组腹腔注射等量PBS。右眼行HE,TUNEL,透射电镜评估视网膜组织损伤的超微结构变化及细胞凋亡程度,左眼取视网膜组织通过Western blot和免疫荧光观察视网膜组织中Rhodopsin和recoverin的mRNA表达变化。
　　结果：透射电镜观察到MNU注射12 h 后出现凋亡小体,24 h后外核层大部分细胞呈阳性反应;TUNEL 检测发现MNU注射24 h 光感受器细胞凋亡指数最高,达(29.7±2.3)%,与电镜结果吻合。 Western blot 结果表明, MNU注射12 h后表达有极显著性差异( P<0.01),而Recoverin的表达从注射后24h有极显著性差异(P<0.01)。
　　结论：一次性腹腔注射60 mg/kg MNU能特异性诱导SD大鼠视网膜光感受器细胞凋亡, Rhodopsin和recoverin表达下调与MNU诱导光感受器细胞的选择性凋亡有关。     

内质网应激参与实验性视网膜脱离后细胞凋亡的研究

目的 研究内质网应激介导凋亡途径的标志物生长停滞及DNA损伤基因153(GADD153)在大鼠实验性视网膜脱离后不同时期的基因与蛋白表达水平并探讨内质网应激与视网膜脱离后细胞凋亡发生的关系.方法 对照实验研究.Wistar大鼠88只(88只眼),采用计算机随机数字表法,分为正常对照组和实验组,实验组包括视网膜脱离后1/2、1、2、4、8、16及32 d组;每组各11只鼠(11只眼),通过在视网膜下注射透明质酸钠的方法,建立视网膜脱离模型.在视网膜脱离后1/2、1、2,4、8、16及32 d分别摘除眼球.应用脱氧核糖核苷酸末端转移酶介导的缺口末端标记法(TUNEL),检测视网膜细胞凋亡情况;采用半定量逆转录聚合酶链反应(RT-PCR)法,检测GADD153 mRNA的表达水平;应用免疫印迹法,检测视网膜组织中GADD153蛋白表达水平;采用免疫荧光和激光共焦显微镜技术,观察GADD153蛋白在视网膜各层细胞的分布.应用SPSS 10.0统计学软件进行数据分析.对各组鼠视网膜凋亡细胞百分比和GADD153 mRNA表达水平的比较,采用Kruskal Wallis 检验;GADD153蛋白表达水平的比较,采用One-Way ANOVA检验,以P＜0.05作为差异有统计学意义.结果 大鼠视网膜脱离后凋亡细胞主要集中在光感受器细胞层,凋亡高峰出现在视网膜脱离后2～4 d,8 d后显著减少,组间视网膜细胞凋亡百分比差异有统计学意义(χ2=22.423,P＜0.05);视网膜脱离后1/2、1、2及4 d,视网膜GADD153 mRNA表达水平显著升高(χ2=27.223,P＜0.05);GADD153蛋白表达水平亦显著升高(F=16.052,P＜0.05),主要表达部位在光感受器细胞层.结论 视网膜脱离后内质网应激标志物GADD153被激活,并在视网膜组织表达水平增高,其表达状态与视网膜细胞的凋亡时间和发生位置相一致;内质网应激介导的凋亡途径参与了视网膜脱离后光感受器细胞凋亡的发生.     

蛇毒神经生长因子对大鼠视网膜缺血再灌注损伤超微结构的影响

目的 探讨玻璃体内注射蛇毒神经生长因子(venom nerve growth factor,vNGF)对实验性大鼠视网膜缺血再灌注(retinal ischemia reperfusion,RIR)损伤的视网膜超微结构是否具有保护作用.方法 采用升高眼压的方法制作实验性RIR损伤大鼠模型.将Spregue-Dawley(SD)大鼠随机分为正常组、缺血组、实验组及对照组.实验组及对照组于再灌注开始时分别注入vNGF和平衡盐溶液各20 μL.通过透射电镜观察各组大鼠视网膜超微结构变化.结果 缺血组主要是视网膜神经节细胞(retinal ganglion cells,RGCs)和光感受器细胞等结构的水肿.对照组再灌注后1 d出现膜盘排列紊乱、变形,RGCs核染色质浓缩、边集、变性,胞浆内细胞器肿胀、空泡化且大量减少.神经纤维内大量的线粒体肿胀、空泡化.至再灌注后7 d膜盘溶解,RGCs出现变性坏死及凋亡;而实验组于再灌注后1 d主要为光感受器细胞排列紊乱、肿胀及RGCs肿胀、少许变性为主,至再灌注后7 d膜盘排列尚整齐,细胞肿胀减轻,胞浆内细胞器较丰富.实验组大鼠视网膜超微结构的改变较对照组明显轻.结论 大鼠玻璃体内注射vNGF对实验性RIR损伤大鼠的视网膜超微结构具有保护作用.     

蓝光诱导的光感受器细胞凋亡与c-Fos蛋白的表达

目的:观察宽谱蓝光诱导Lewis大鼠视网膜光损伤后光感受器细胞的凋亡及c-Fos蛋白的表达。方法:8～10wk龄雌性Lewis大鼠24只,在循环光环境下饲养并随机分为6组。暗适应24h后,5组接受3012×115Lux的宽谱蓝光(400～500nm)照射1h,光照后予暗适应并于0,6,12,24及48h颈椎脱位法处死大鼠,摘除眼球;另1组为正常对照组,不予光照。采用透射电镜及TUNEL试剂盒检测视网膜细胞凋亡,免疫组化法检测视网膜内c-Fos蛋白的表达。结果:蓝光可特异性引起大鼠光感受器细胞凋亡和光感受器细胞内c-Fos蛋白的表达上调。光照后外核层细胞开始出现凋亡,24h达峰值,大量光感受器细胞出现核固缩并可见凋亡小体形成。c-Fos蛋白的表达在时间与空间分布上与TUNEL阳性细胞基本一致,在同一时间点,二者呈正相关(r =0.905,P <0.05)。结论:蓝光可诱导大鼠光感受器细胞凋亡,视网膜外核层中c-Fos蛋白的表达上调对视网膜蓝光损伤后光感受器细胞凋亡可能具有重要作用。     

A microscopic study of herpes simplex virus retinopathy in mice

ICR white mice were inoculated with herpes simplex virus (HSV) type I in the anterior chamber of one eye. Animals were killed at intervals of 2, 4, 6, 8, and 10 days and both eyes were obtained for light and electron microscopic study of retinal changes. HSV retinopathy developed in 42 (91%) of 46 inoculated eyes. Fourteen (88%) of sixteen noninoculated eyes examined after the sixth postinoculation day developed HSV retinopathy. The earliest signs of retinopathy in the inoculated eye were peripheral retinal vasculitis and inflammatory cells throughout the nerve fiber layer on day 2. No virus was found in retinal tissue until day 4, at which time disruption of outer retinal layers (outer nuclear layer and layer of rods and cones) was observed in the peripheral retina. The earliest signs of retinopathy in the noninoculated eye were isolated foci of outer retinal disruption in the posterior retina on day 6. The inflammation accompanying early retinal changes of HSV retinopathy were more severe in the inoculated eye. Electron microscopy of both eyes revealed viral particles in the inner nuclear and ganglion cell layers at the time of outer retinal disruption, but viral particles were seen only rarely in the outer retinal layers at this stage. Early disruption of normal retinal architecture may be due to infection and destruction of Muller cells. The retinopathy progressed in both eyes to total destruction of the retina by day 10. Viral infection of the retinal pigment epithelium occurred, but viral particles were seen only rarely in the underlying choroid. This model may be useful for the study of HSV retinopathy in humans.     

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）     

Apoptosis and caspases after ischemia-reperfusion injury in rat retina

PURPOSE: Extensive cell loss in the retinal ganglion cell layer (RGCL) and the inner nuclear layer (INL) was noted in a rat model of retinal ischemia-reperfusion injury by transient elevated intraocular pressure (IOP). The possible involvement of apoptosis and caspases was examined in this model of neuronal loss. METHODS: Transient elevated IOP was induced in albino Lewis rats through the insertion of a needle into the anterior chamber connected to a saline column. Elevated IOP at 110 mm Hg was maintained for 60 minutes. Groups of animals were euthanatized at various times after reperfusion, and their retinas were evaluated by morphology, agarose gel electrophoresis of DNA, in situ terminal deoxynucleotidyl transferase-mediated biotin-deoxyuridine triphosphate nick-end labeling (TUNEL), immunohistochemistry of caspases II (ICH1) and III (CPP32), and morphometry. YVAD.CMK, a tetrapeptide inhibitor of caspases, was used to examine the involvement of caspases. RESULTS: A marked ladder pattern in retinal DNA gel analysis, typical of internucleosomal DNA fragmentation and characteristic of apoptosis, was present 12 and 18 hours after reperfusion. Labeling of nuclei in the RGCL and the inner nuclear layer (INL) by TUNEL was noted between 8 and 18 hours after reperfusion. Histologic and ultrastructural features typical of apoptosis were also observed in the inner retina after ischemia. YVAD.CMK administered during the ischemic period inhibited apoptotic fragmentation of retinal DNA and ameliorated the tissue damage. When administered intravitreally 0, 2, or 4 hours after reperfusion, YVAD.CMK was also effective in preserving the inner retina but had no significant effect when administered 6 or 8 hours after reperfusion. The inner retina showed transient elevated immunoreactivity of caspases II and III 4 and 8 hours after reperfusion. CONCLUSIONS: Retinal ischemia-reperfusion after transient elevated IOP induced apoptosis of cells in the retinal ganglion cell layer and the INL. Caspases may have a pivotal role in the early events of the apoptotic pathway(s). Rescue by using anti-apoptotic agents after ischemia-reperfusion is feasible.     

Neuroprotective Effects of Granulocyte Colony-Stimulating Factor on Ischemia-Reperfusion Injury of the Retina

Purpose: It has been reported that granulocyte colony-stimulating factor (G-CSF) provides neuroprotection in models in which neuronal cell death is induced. This research was designed to investigate the effects of G-CSF on neurodegeneration of the inner retinal layer in a rat model of ischemic reperfusion (I/R) injury. Materials and Methods: Retinal ischemia was induced by increasing the intraocular pressure to 110 mm Hg for 45 min in the left eyes of the rats. A sham operation was carried out on the right eyes. G-CSF (100 μg/kg/day in 0.3 ml saline) or the same volume of saline was intraperitoneally injected just before the operation and continued for 4 consecutive days (a total of 5 consecutive days). Morphological examinations, including the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, were performed 7 days after I/R induction. The expression of phosphorylated AKT in the retina was examined by Western blot analysis and immunohistochemistry. Results: Cell loss in the ganglion cell layer was more significantly reduced in the I/R-induced eyes of the G-CSF-injected rats than in the I/R-induced eyes of the saline-injected rats (20.3 vs. 6.6%). The inner retinal thickness ratios, such as the inner plexiform layer to the inner limiting membrane/outer nuclear layer and the inner nuclear layer/outer nuclear layer, were significantly better preserved in the I/R-induced eyes of the G-CSF-injected rats than in the I/R-induced eyes of the saline-injected rats. TUNEL assays showed fewer apoptotic cells in the retinal sections of the I/R-induced eyes of the G-CSF-injected rats. The phosphorylation of AKT (p-AKT/AKT) was upregulated in the retinas of the I/R-induced eyes of the G-CSF-injected rats. Conclusion: Our results demonstrated that systemic injection of G-CSF can protect retinal ganglion cells and inner retinal layers from I/R injury. The effects could be associated with the activation of AKT.     

N-methyl-D-aspartate (NMDA)--induced apoptosis in rat retina.

PURPOSE: The involvement of apoptosis in N-methyl-D-aspartate (NMDA)-induced excitotoxicity in adult rat retinas was examined. METHODS: Excitotoxic loss of inner retinal elements was induced by intravitreal injections of various concentrations of neutralized NMDA in adult albino Lewis rats. Tissue responses were quantified by measuring the inner retinal thickness (IRT) in plastic sections of the retinas and cell counts in the retinal ganglion cell layer in flatmount preparations of the whole retinas. Internucleosomal DNA fragmentation, a hallmark of apoptosis, was assayed with agarose DNA gel electrophoresis. The in situ TdT-mediated biotin-dUTP nick end labeling (TUNEL) method was used to locate nicked DNA in paraffin sections of the retinas. Ultrastructural changes of the degenerating cells were examined by electron microscopy. The efficacy of Ac-Tyr-Val-Ala-Asp-CMK (YVAD-CMK), a peptidyl caspase inhibitor, and 3-aminobenzamide (ABA), an inhibitor of poly(ADP-ribose) polymerase (PARP), in ameliorating the loss of inner retinal elements was evaluated using morphometry to examine the apoptotic pathways. RESULTS. Intravitreal injection of NMDA induced a dose-dependent loss of inner retinal elements as evidenced by the measurements of IRT and RGCCs. There were time- and dose-related appearances of internucleosomal fragmentation of retinal DNA and a time-related appearance of TUNEL-positive nuclei in the inner retinas after intravitreal NMDA injection. Ultrastructural features consistent with classic apoptotic changes were noted in degenerating cells in the retinal ganglion cell layer and the inner nuclear layer. Control retinas given vehicle, N-methyl-L-aspartate (the L-isomer of NMDA), or NMDA plus MK-801, a specific antagonist, did not show these changes. Simultaneous administration of NMDA and YVAD-CMK or ABA abolished or attenuated the loss of RGCCs in the posterior retinas. CONCLUSIONS. NMDA-induced excitotoxicity involved apoptosis and caspases and PARP may play important roles in the pathways.     

Effects of nerve growth factor for retinal cell survival in experimental retinal detachment

PURPOSE: To investigate the neuron protective effect of recombined nerve growth factor (rNGF) on retinal cell damage induced by experimental retinal detachment. METHODS: Experimental retinal detachment models were created in Sprague-Dawley rats by subretinal injection of sodium hyaluronate. Intravitreal injection of rNGF (5 microg/eye) or phosphate-buffered saline (PBS) was separately applied every 4 days after retinal detachment. The rat eyes were then observed and sacrificed at various time points. Morphologic changes were observed by light microscopy, electron microscopy, and cell counts. Apoptosis of retinal cells was detected by TUNEL assay. RESULTS: After retinal detachment, most eyes from NGF-treated groups showed better organized structure of retinal cells than those from the PBS-treated control groups. Cell counts indicated that the nuclei numbers in the outer nuclear layer (ONL), inner nuclear layer (INL), and ganglion cell layer (GCL) of NGF-treated groups were significantly more than those from PBS-treated control group (p < 0.05) after retinal reattachment. TUNEL-positive cells were identified in ONL, INL, and GCL. They peaked at the fourth day after retinal detachment in both the NGF-treated groups and the control groups. But the cell counts of apoptosis revealed that the NGF-treated retina had less TUNEL-positive cells than the control groups (p < 0.05). CONCLUSIONS: The results showed that intravitreal injection of exogenous NGF can protect retinal cells from degeneration and apoptosis in experimental retinal detachment. It may exert its neuroprotection effect by preventing the apoptosis of retinal cells after retinal detachment.     

Apoptosis of photoreceptor cells in ornithine-induced retinopathy

• Background: The intravitreal injection of ornithine produces selective damage to the retinal pigment epithelium (RPE) and results in a loss of RPE, choriocapillaris and photoreceptor cells. To elucidate the mechanism of secondary retinal atrophy, we investigated the presence of apoptotic cells in a rat model of ornithine-induced retinopathy. • Methods: At 6 and 12 h and 1, 2, 4, 7, 14 and 28 days after an intravitreal injection of L-ornithine hydrochloride in rat eyes, we removed the eyes and subjected them to histopathological examination. We detected apoptotic cells by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate digoxigenin nick end labeling (TUNEL) assay, which stains the 3′-OH ends of fragmented DNA. We used electron microscopy to detect the apoptotic cells morphologically. • Results: RPE cells were selectively damaged immediately after ornithine administration. TUNEL-positive photoreceptor cells appeared exclusively in the photoreceptor cell layer 12 h after ornithine administration. The number of TUNEL-positive cells increased throughout the 2 days following the injection, then decreased markedly. TUNEL-positive cells remained until 28 days, when the photoreceptor cells had disappeared. The ganglion cell layer, inner nuclear layer and damaged RPE cells were negative for TUNEL staining during all stages. The electron microscopic study also revealed the pyknotic nuclei of apoptotic photoreceptor cells. • Conclusion: An intravitreal injection of ornithine caused primary damage to the RPE, and subsequently some of the photoreceptor cells revealed apoptosis by TUNEL assay. These findings suggest the dysfunction of the RPE causes photoreceptor cell death according to the intrinsic program of an apoptotic mechanism. Received: 16 April 1997 Revised version received: 7 July 1997 Accepted: 18 July 1997