The effects of indocyanine green and endoillumination on rabbit retina: an electroretinographic and histological study

AIM: To evaluate the functional and morphological retinal toxicity associated with intravitreal injection of indocyanine green (ICG) dye in rabbit eyes during vitrectomy with endoillumination. METHODS: 20 eyes of 10 New Zealand pigmented rabbits were used in the study. All eyes underwent pars plana vitrectomy and removal of posterior vitreous cortex under endoillumination. In one eye of each rabbit, intravitreal injection of 0.1 ml of 2.5 mg/ml ICG was applied for 30 seconds followed by 10 minutes of endoillumination. The control eye had endoillumination only without ICG injection. Dark adapted and light adapted electroretinograms (ERGs) were performed before the surgery and 1 week after surgery for serial comparisons. Rabbits were killed 1 week after surgery and eyes were enucleated for histological examination. RESULTS: Serial ERG comparisons showed significant reduction in the light adapted a-wave amplitude (p = 0.037) and significant delays in the dark adapted and light adapted b-wave latencies (p = 0.020 and p = 0.038, respectively) in the ICG treated eyes. Histological examinations demonstrated loss of photoreceptor outer segments with focal absence of photoreceptors in some areas in the ICG injected eyes. CONCLUSIONS: Vitrectomy followed by intravitreal injection of 2.5 mg/ml ICG for 30 seconds with endoillumination may result in retinal toxicity causing functional and morphological retinal damages in rabbit eyes. The lowest concentration of ICG should be used if necessary for intraocular use to prevent potential retinal toxicity.     

Long-term observation of fundus infrared fluorescence after indocyanine green-assisted vitrectomy

PURPOSE: To observe the persistence of infrared fluorescence after indocyanine green (ICG)-assisted vitrectomy. METHODS: Eighteen consecutive patients underwent ICG-assisted vitrectomy for eyes with macular holes, epiretinal membranes, diabetic macular edema, and macular edema due to retinal vein occlusion. The internal limiting membrane was peeled after staining with 0.42% ICG solution. Postoperative observation of fundus infrared fluorescence was carried out using Heidelberg Retina Angiography (Heidelberg, Germany). RESULTS: Within a few months after surgery, intense fluorescence was observed around the macular hole and on the optic disk, photocoagulation scars, and the optic nerve fiber and was especially strong in the area along the vascular arcade. At the final visit (16-36 months after surgery), 12 (67%) of 18 eyes had infrared fluorescence that included fluorescence corresponding to the macular hole, retinal edema, and photocoagulation scars. The fluorescence over chorioretinal atrophy in a highly myopic eye disappeared compared with the area having an intact retinal pigment epithelium. CONCLUSIONS: Infrared fluorescence from ICG persists for 16 months to 36 months after ICG-assisted vitrectomy. ICG introduced directly into the vitreous cavity may remain in the eye over years. Careful long-term observation for the adverse effects of ICG is needed.     

Vitrectomy with fluconazole infusion: retinal toxicity, pharmacokinetics, and efficacy in the treatment of experimental candidal endophthalmitis.

The aim of this study was to determine the retinal toxicity and intraocular pharmacokinetics of vitrectomy with fluconazole infusion in rabbit eyes and to study its efficacy in the treatment of experimental candidal endophthalmitis. The right eyes of 13 New Zealand White (NZW) rabbits were vitrectomized and infused with 20 mL of 0.2 mg/mL, 1 mg/mL, or 2 mg/mL of fluconazole. An electroretinogram (ERG) was performed on both eyes of each rabbit at different time points. The right eyes of 26 different NZW rabbits were vitrectomized and infused with 20 mL of 2 mg/mL of fluconazole. These rabbits were sacrificed, and their right eyes were enucleated at hours 2, 4, 8, and 24 after the operation, and the concentration of fluconazole in the vitreous was measured by highpressure liquid chromatography. Experimental candidal endophthalmitis was induced in the right eye of 42 other NZW rabbits. Twenty-six (26) of the eyes were then vitrectomized and infused with 20 mL of 2 mg/mL of fluconazole, and the other 16 rabbits served as control. Severity of ocular infection was graded from 0-4 at different time intervals, using an indirect ophthalmoscope. In the first group, ERG showed no significant difference between the experimental eyes and the control eyes--in all concentrations of fluconazole--for up to 3 months. In the second group, the intraocular concentration of fluconazole declined so rapidly that, as of 8 hours after operation, there was none in the vitreous cavity. In the third group, significantly less vitreous opacity was found in the treated eyes on days 3 and 6. However, the difference ceased to be apparent on day 15. Our study suggests that there is no retinal toxicity resulting from vitrectomy with a 2 mg/mL fluconazole infusion, and that it is temporally effective in the treatment of experimental candidal endophthalmitis.     

Persistence of fundus fluorescence after use of indocyanine green for macular surgery

PURPOSE: To investigate the possible persistence and characteristics of infrared fluorescence of the fundus for several months after surgery with intraocular injection of indocyanine green (ICG). DESIGN: Interventional, noncomparative, prospective case series. PARTICIPANTS: Seventeen patients operated on in our department with ICG injection into the vitreous cavity, who gave prior informed consent. METHODS: After standard three-port pars plana vitrectomy and posterior vitreous detachment, 0.1 to 0.2 ml of an ICG solution at a concentration of 2.5 mg/ml was injected through a 5- micro m sterile filter over the posterior pole and left in place for 3 minutes. The stained internal limiting membrane was then peeled off. Patients had postoperative infrared fundus photographs at each consultation in our department. Follow-up ranged from 1 to 7 months. Visual acuity and any unexpected event were also recorded. MAIN OUTCOME MEASURES: Postoperative infrared fluorescence of the fundus. RESULTS: The day after surgery, no green ICG staining of the fundus was visible on biomicroscopy. However, infrared photography showed diffuse fluorescence of the fundus. At 1 and 3 postoperative months, infrared fundus photography showed an intensely fluorescent optic nerve disc. In patients with macular hole, the center of the macula also exhibited faint granular fluorescence. At 6 months postoperative or later, only the optic disc remained fluorescent, but the fluorescence was far less intense than at 3 months. Infrared photographs of the fellow eyes exhibited no fluorescence. Visual acuity improved or was unchanged compared with preoperative vision in 16 eyes and decreased by 1 line in 1 eye. CONCLUSIONS: After intraoperative use of ICG for macular surgery, fluorescence of the optic disc and of the macular center after macular hole surgery persisted for months in all cases. ICG may accumulate in the macular pigment epithelium and optic nerve, raising the problem of the as yet unknown pharmacokinetics of ICG after intravitreous administration and of its long-term safety.     

Retinal function after vitrectomy

PURPOSE: To study retinal function after vitrectomy. METHODS: Core vitrectomy was performed in 12 rabbits under standardized conditions using a vitreous cutting rate of either 600 or 1200 cuts/min. Full-field electroretinography (ERG) and multifocal electroretinography (mfERG) were performed pre- and postoperatively. Morphologic change was monitored by immunohistochemistry directed against glial fibrillary acidic protein (GFAP). RESULTS: Three days postoperatively, the b-wave amplitudes of all cone and rod responses of the ERG were significantly reduced in all vitrectomized eyes. At 28 days, the rod response was still reduced, but returned to normal by 58 days. No correlation was found between vitreous cutting speed and ERG findings. No reduction in the central cone function was detected in the mfERG. GFAP upregulation was found in the entire retina of vitrectomized eyes 3 days after surgery. GFAP expression was present after 28 and 58 days in eyes in which the vitreous cutting rate had been set to 600 cuts/min, but not in the 1200 cuts/min eyes. CONCLUSION: Pars plana vitrectomy transiently affects retinal function in rabbit eyes. Vitreous cutting speed is not related to the reduced function but appears inversely correlated to Müller cell activation, indicating that high-speed vitreous cutters are more lenient to the retina.     

Retinal function and histologic changes following intravitreal injection of indocyanine green in a rabbit model.

The aim of this animal study was to investigate the effects of intravitreal injection of indocyanine green (ICG) applied in macular hole surgery on retinal functional, morphology, and histologic changes. Eighteen (18) New Zealand albino rabbits were divided equally into three groups (6 rabbits in each). In Group A, both eyes of each rabbit were vitrectomized by perflouropropane gas compression. One (1) month later, 0.1 cc of different doses of ICG was injected into the vitreous in the left eyes. In the right eyes, 0.1 cc of balanced salt solution was injected intravitreally, allowing them to serve as control eyes. In Group B, the same doses of ICG were injected intravitreally. ICG was washed out by fluid-fluid exchange 3 minutes after injection. In Group C, the same doses of ICG were injected intravitreally in nonvitectomized eyes. Scotopic and photopic electroretinogram (ERG) recordings and indirect ophthalmoscopy examinations were performed to detect any functional and morphologic changes. Rabbit eyes were enucleated 4 months after ICG injections to observe histologic changes. Significant decreased of scotopic and photopic ERG amplitude and marked histologic changes were noted in eyes injected with 0.5 mg/cc and 0.1 mg/cc of ICG in nonvitrectomized eyes (Group C). In vitrectomized eyes (Group A), decreased scotopic and photopic ERGs and mild histologic changes were noted in eyes injected with 0.5 mg/cc, but no histologic changes were noted in eyes injected with 0.1 mg/cc. There was a transient, mild decrease in scotopic and photopic ERGs and no morphologic changes were noted in the eyes with fluid-fluid exchange (Group B). The toxicity of intravitreous ICG is dose- and time-dependent. ICG at 0.5 mg/cc, with short exposure time, is recommended in macular hole surgery.     

Morphological and functional damage of the retina caused by intravitreous indocyanine green in rat eyes

BACKGROUND: This study was designed to investigate the influence of intravitreal indocyanine green (ICG) on retinal morphology and function. METHODS: Brown Norway rats eyes ( n=24) were vitrectomized by the injection of 0.05 ml of 100% SF(6) gas. Two weeks later, ICG solution was injected into the vitreous cavity of vitrectomized eyes at a dose of 25 mg/ml, 2.5 mg/ml, 0.25 mg/ml or 0.025 mg/ml (0.05 ml/eye). Retinal toxicity was histologically assessed by light microscopy on day 10. The retinal function was also evaluated by electroretinography (ERG) in the low-dose groups (0.25 mg/ml and 0.025 mg/ml) after 10 days and again after 2 months,. Sham-operated eyes (SF(6) injected followed by 0.05 ml of BSS plus, n=6) were used as controls. RESULTS: In the high-dose group (25 mg/ml ICG), the retinal structure was severely deformed and the retinal pigment epithelium partly disappeared. In eyes with 2.5 mg/ml ICG, the retinal structure was also affected but less strongly so than with 25 mg/ml. No apparent pathologic change was observed in the low-dose groups (0.25 mg/ml or 0.025 mg/ml) by light microscopy. In contrast, 10 days later the amplitude of dark-adapted a- and b-waves of ERGs in the eyes of low-dose group rats were found to have decreased. In addition the light-adapted b-waves did not change significantly. These changes remained for 2 months. CONCLUSION: Even at a low dose (0.025 mg/ml), intravitreous ICG induced functional damage of the retina without any apparent morphological damage. This information should be taken into account when clinically administering ICG into the vitreous cavity.     

Polylactic acid for visualizing the vitreous body during vitrectomy

PURPOSE: To investigate the possibility of using polylactic acid (PLA) as a surgical adjuvant for visualizing the vitreous body during vitrectomy. METHODS: After a core vitrectomy, 1 mL of PLA suspension was injected into the rabbit vitreous in two groups: group A, 2.5% PLA (n = 5), and group B, 1% PLA (n = 9). Vehicle injection instead of PLA was used as a control (group C, n = 5). The clinical signs and electroretinogram (ERG) were evaluated for 28 days, and histologic findings were evaluated on day 28. Next, intraocular pressure (IOP) after intracameral injection of a PLA suspension was evaluated in the rabbits (n = 6). Last, the visualization of the vitreous body by PLA suspension was evaluated during vitrectomy in monkey eyes (n = 4). RESULTS: The white granules of PLA disappeared from the vitreous cavity in 10 eyes within 3 weeks; however, a small amount of PLA remained in four eyes for 4 weeks. Mild inflammation of the anterior chamber was observed in one eye in group B and 1 eye in group C. No cataract or retinal hemorrhage was found in any eyes. The amplitude of ERG on each time point did not differ between the groups. IOP remained within normal range except for the initial spike. Retinal structure was well preserved histologically. During vitrectomy in monkey eyes, the vitreous body was well visualized, and the posterior vitreous separation was performed easily and safely. CONCLUSIONS: PLA can be a new surgical adjuvant to visualize the vitreous body during vitrectomy.     

活体猪眼行放射状视神经切开术后的 组织病理学观察

目的观察活体猪眼行放射状视神经切开术（RON）后的病理改变过程，为临床RON安全性提供实验依据。方法健康小型猪共12只，其中8只双眼行RON后，分别于1、3、7、48 d处死，每天各处死2只猪；2只猪一只眼行RON，另一只眼作正常对照；2只猪一只眼行RON，另一只眼行单纯玻璃体切除，于120 d后处死。取出眼球后常规制作石蜡组织切片行苏木精-伊红染色、Masson三色染色或Luxol 坚固蓝染色，光学显微镜下对不同水平的视神经断面进行观察。结果所有眼球大血管壁未被破坏，球后视神经的软脑膜保持完整。手术后第1天可见创口形成，局部出血向周围及后方浸润，神经纤维髓鞘脱失所致的空泡样改变局限在创口内。手术后第3天时可见空泡样改变范围扩大。手术后第7天创口成纤维细胞密集，神经胶质细胞增生及分散的色素颗粒存在，浸润的炎性细胞以淋巴细胞和单核细胞为主。手术后第48天视盘创口胶原成分填充，切开深度未及的后方视神经局部神经胶质细胞密集，坚固蓝染色浅淡，边界清晰，其范围部分越过中线。手术后第120天创伤下方部位呈现局部视神经萎缩性改变。正常眼及单纯玻璃体切除眼切片光学显微镜观察未见病理改变。结论正常活体猪眼行RON后最终形成局部视神经萎缩，一定程度上手术本身是安全的。(中华眼底病杂志,2005,21:13-15)     

神经生长因子对成年兔视神经夹伤后 修复的影响

目的研究神经生长因子(NGF)对成年兔视神经夹伤后修复的影响。方法16只成年兔随机分成NGF组和对照组,每组8只兔。建立兔右眼视神经夹伤模型后分别将载有0.06 ml NGF（浓度:5×10-4g/L,NGF组）或等量磷酸盐缓冲液（PBS）（对照组）的组织工程化神经移植于视神经损伤处；并向右眼玻璃体腔内注入0.02 ml NGF（浓度:5×10-4 g/L ,NGF组）或等量PBS（对照组）。所有兔左眼为正常空白对照组。分别于夹伤后1 d、2周、8周进行闪光视觉诱发电位(FVEP)检查。夹伤后8周时作光学显微镜和电子显微镜检查观察视网膜神经节细胞(RGC)和视神经的改变，同时用计算机图像处理系统作视神经纤维计数。结果夹伤后2周时FVEP检查结果显示，NGF组伤眼与健眼FVEP幅值比为0.765±0.150，对照组为0.494±0.108， NGF组与对照组相比差异有统计学意义（P<0.01）。夹伤后8周时NGF组伤眼与健眼FVEP幅值比为0.581±0.138，对照组为0.409±0.119， NGF组与对照组相比差异有统计学意义（P<0.05）。夹伤后8周时的光学显微镜和电子显微镜检查结果显示：NGF组RGC、视神经纤维的退变较对照组轻。夹伤后8周时NGF组和对照组视神经纤维计数分别为（10 955±608.7）、（7 898±608.8）根/ mm²，两组间差异有统计学意义（P<0.001）。结论NGF能够在一定程度上增加RGC的存活，促进轴突的再生，因而对视神经夹伤后的修复、视功能的恢复具有一定的促进作用。(中华眼底病杂志,2005,21:253-257)     

全氟己基正辛烷对视网膜的毒性作用

目的 观察全氟己基正辛烷（F6H8）对兔视网膜组织结构的影响。方法 新西兰白兔15只，玻璃体切割术后玻璃体腔内注入F6H8（实验组12只）或平衡盐溶液（balanced salt solution,BSS)(对照组3只）2ml，手术前后定期裂隙灯、间接检眼镜检查，手术后并行组织学和透射电镜检查。结果 F6H8在玻璃体腔内形成单个透明泡，未见视网膜脱离及白内障。实验组兔眼组织学检查，手术后4周开始下方视网膜出现外丛状层水肿，继而变薄，部分内、外核层细胞变性，电镜下见细胞空泡变性。结论 F6H8玻璃体腔内填充对视网膜有一定的毒性作用，目前尚不宜用作眼内长期填充物。     

Effects of lens extirpation with anterior vitrectomy on vitreous three-dimensional mesh structure

AIM: To investigate the changes in vitreous gel structure after lens extirpation combined with anterior vitrectomy in rabbit eyes. METHODS: Twenty-eight chinchilla rabbits were divided into three groups. The control group (Group I) included 16 eyes from eight rabbits who did not receive any treatment. Group II included 20 eyes from 10 rabbits that underwent lens aspiration only. Group III included 20 eyes from 10 rabbits that underwent lens aspiration combined with posterior capsulotomy and anterior vitrectomy. Eyes were harvested on the 30th and 60th day postoperatively, respectively. Changes in vitreous gel stretch length due to gravity and the rate of vitreous liquefaction were observed. The collagen content in the vitreous body was examined using the L-hydroxyproline test. Electronic microscopic images were obtained from each eyeball. RESULTS: On both the 30th and 60th day postoperatively, the vitreous gel length of group III was significantly shorter than group I and group II (P<0.05), while the rate of liquefaction of the vitreous body in group III was significantly higher than group I and group II (P<0.05). The collagen content in group III was also higher than that in group I and group II (P<0.05). CONCLUSION: Loss of vitreous gel mass is more likely to occur in the eyes of rabbits receiving anterior vitrectomy. Lensectomy combined with anterior vitrectomy may damage the stable three-dimensional mesh structure of collagen, which could aggravate vitreous gel liquefaction.     

The inflammatory role of endotoxin in rabbit gram-negative bacterial endophthalmitis

The authors used the limulus lysate assays to measure the amount of gram-negative endotoxin produced in two rabbits with experimentally induced gram-negative (Escherichia coli) endophthalmitis. A similar amount of purified enodotoxin was injected into the eyes of 14 rabbits to determine the rate of clearance of endotoxin from the rabbit eyes. Endotoxin was found in clinically inflammatory quantities 2 weeks after injection. Results of pathologic examination showed that endotoxin incites severe inflammatory responses in the eye, affecting the ciliary body, vitreous, choroid, retina, and optic nerve. These results suggest that the limulus lysate assay may be useful for detecting early gram-negative endophthalmitis, and that in such cases, early emergency vitrectomy may be needed to remove the inflammation-inciting endotoxin and preserve useful vision.     

乳兔雪旺细胞对成兔视神经挫伤修复的作用

目的 研究乳兔雪旺细胞(Schwann cell,SC)对成兔视神经挫伤修复的作用。 方法 建立成兔视神经挫伤模型,伤后24 h分别向伤眼玻璃体腔内注入SC悬液(A组)、生理盐水(B组)各0.1 ml。伤后不同时间点进行视网膜节细胞(retinal ganglion cell,RGC)、轴突染色记数及闪光视觉诱发电位(flash visual evoked potentials,FVEP)检测。 结果 伤后4周A、B组RGC平均记数分别为(19.89±3.79) /mm和(12.67±4.12) /mm,轴突密度分别为(94.569±793) /mm ²和(36.085±285) /mm²,A组明显高于B组(P<0.01)。伤后3 d A组伤眼与健眼FVEP幅值比由48%上升至88%,8周时仍为78%,各时间点均明显高于B组(P＜0.01)。 结论 乳兔SC能够提高成兔视神经挫伤后RGC存活率,减轻轴突变性,显著促进视神经功能恢复,对视神经挫伤修复具有明显的促进作用。(中华眼底病杂志,2000,16:91-93)      

Measurement of amino acid levels in the vitreous humor of rats after chronic intraocular pressure elevation or optic nerve transection

PURPOSE: To investigate whether the levels of free amino acids and protein in the vitreous of rat eyes are altered with chronic intraocular pressure (IOP) elevation or after optic nerve transection. MATERIALS AND METHODS: The concentrations of 20 amino acids in the vitreous humor were measured by high-performance liquid chromatography in both eyes of 41 rats with unilateral IOP elevation induced by translimbal photocoagulation. Eyes were studied 1 day and 1, 2, 4, and 9 weeks after initial IOP elevation. The same amino acids were measured in 41 rats 1 day and 2, 4, and 9 weeks after unilateral transection of the orbital optic nerve. The intravitreal protein level was assayed in additional 22 rats with IOP elevation and 12 rats after nerve transection. Two masked observers evaluated the amount of optic nerve damage with a semiquantitative, light-microscopic technique. RESULTS: In rats with experimental glaucoma, amino acid concentrations were unchanged 1 day after treatment. At 1 week, 4 of 20 amino acids (aspartate, proline, alanine, and lysine) were higher than in control eyes ( < or = 0.01), but this difference was nonsignificant after Bonferroni correction for multiple simultaneous amino acid comparisons (none achieved < 0.0025). No amino acid was significantly different from control in the nerve transection groups (all > 0.05). Vitreous protein level was significantly higher in glaucomatous eyes than their paired controls at 1 day ( < 0.0001) and 1 week ( < 0.002). One day and 1 week after optic nerve transection, vitreal proteins were significantly elevated compared with control eyes from untreated animals ( < 0.0020 and < 0.0022, respectively), though not compared with their fellow eyes ( = 0.25 and 0.10). CONCLUSION: Chronic experimental glaucoma and transection of the optic nerve increase the amount of protein in the rat vitreous above control levels. In the vitreous of rats with experimental glaucoma, a number of free amino acids were transiently elevated to a modest degree, but no significant difference in vitreous glutamate concentration was detected ( > 0.01).     

超声微泡造影剂联合美金胺增强视神经损伤大鼠视网膜神经节细胞保护作用

目的 探讨超声微泡造影剂联合美金胺对视神经损伤大鼠视网膜神经节细胞( RGC)的保护作用.方法 将Sprague-Dawley(SD)雄性成年大鼠40只随机分为正常对照组(A组),假手术组(B组),空白对照组(C组),玻璃体腔单独注射美金胺组(D组),玻璃体腔注射美金胺加超声微泡组(E组)5个组,每组8只大鼠,再将各组随机分为视神经损伤后1、2周2个亚组,各亚组4只大鼠.A组不做任何处理;B组只暴露视神经,不进行钳夹,玻璃体腔注射生理盐水,立即用超声波辐照大鼠眼球;C～E组建立视神经钳夹伤模型后,处理方式分别为C组玻璃体腔注射生理盐水,D组玻璃体腔注射美金胺,E组玻璃体腔注射超声微泡造影剂及美金胺,立即用超声波辐照大鼠眼球.视神经损伤1、2周时,各组行逆行荧光金标记RGC并计数;闪光视觉诱发电位(F-VEP)检测,记录P100波潜伏期及振幅;荧光电子显微镜下观察视网膜细胞形态学改变.结果 逆行荧光金标记RGC结果显示,各处理组视网膜定向铺片上均可见金黄色着染的RGC.A、B组RGC数间差异无统计学意义(q=0.018,0.011;P=0.986,0.873);C～E组RGC数均较A组减少,差异具有统计学意义(F=85.944,P=0.012);D组RGC数多于C组,差异具有统计学意义(q=1.721,1.924;P=0.043,0.037);E组RGC数明显高于C、D组,差异具有统计学意义(q=1.128,1.482,P=0.027,0.008;q=1.453,1.855,P=0.031,0.010).F-VEP检测发现,A、B组P100波潜伏期及振幅间差异无统计学意义(q=0.008,0.019,P=0.981,0.946;q=0.072,0.052,P=0.737,0.851) ;C～E组P100波潜伏期较A组延长,振幅较A组降低,差异具有统计学意义(F=134.312,106.312;P=0.017,0.009).荧光电子显微镜下观察发现,A、B组大鼠视网膜各层结构完整,排列整齐,RGC排列紧密整齐,细胞核均匀深染,胞核大小一致.C～E组大鼠的视网膜不同程度水肿变厚,RGC有不同程度的排列紊乱,空泡化及细胞数目减少.结论 超声微泡造影剂联合美金胺能抑制视神经损伤后大鼠RGC的丢失,促进其视功能的恢复,对视神经损伤大鼠的RGC具有保护作用.     

Caspase-3抑制剂Z-DEVD—FMK对兔外伤性视神经的保护作用

目的观察caspase-3抑制剂Z—DEVD—FMK对兔外伤性视神经损伤后的神经保护作用。方法中国纯种大耳白兔104只,从中随机选取8只兔（16只眼）作为空白对照组（N组,不作任何处理）,其余96只（192只眼）作为实验组,实验组再分为玻璃体腔注射组和眼周注射组．每组48只（96只眼）。玻璃体腔注射组中每只兔的右眼为caspase-3抑制剂注射组（A组）,左眼为玻璃体腔DMSO液注射组（B组）。眼周注射组中每只兔的右眼为球周caspase-3抑制剂注射组（C组）,左眼为球周DMSO液注射组（D组）。又根据给药后不同的观察时间将每组分为1d组、4d组、7d组、10d组、14d组、21d组六个亚组,每个亚组8只眼。应用液压冲击颅脑损伤仪（fluid percussion brain ijury device,FPI）建立免视神经损伤动物模型,分别于术后第1、第4、第7、第10、第14、第21天进行闪光视觉诱发电位（flash—visual evoked potential．F—VEP）、眼眶核磁共振（nuclear magnetic resonance imaging,MRI）检查,并应用TUNEL技术检测视网膜神经节细胞（retinal ganglion cell,RGC）的凋亡。数据采用SPSS12．0统计软件,行单因素以及析因方差分析。结果①F—VEP：在术后第7、第10、第14和第21天,A组和C组的主波潜伏期逐渐缩短．振幅逐渐升高．与B组和D组相比差异均有统计学意义（P〈0．05）。A组和C组主波潜伏期在术后第4天虽然仍在延长,但与B组和D组比较差异有统计学意义（P〈0．05）,A组伤后第21天的潜伏期和振幅分别为（65．46±6．97）ms和（6．75±2．75）mV,C组分别为（72．06±6．57）ms和（6．02±1．98）mV．两组比较差异有统计学意义（P〈0．05）。空白对照组潜伏期和振幅与其他各组的相应时间点比较,差异均有统计学意义（P〈0．05）。②MRI：A组和C组的视神经MRI可见,伤后第7天粗大的视神经开始消退,至第14、第21天水肿     

Hemostatic effects of air versus fluid in diabetic vitrectomy

The potential hemostatic effect of an intravitreal air bubble after diabetic vitrectomy was studied in an animal model and in a randomized clinical trial. One day after vitrectomy with induced intraoperative hemorrhage, vitreous cavity hemorrhage was present in 60% of air-filled rabbit eyes compared with 27% of fluid-filled eyes. The prevalence and extent of hemorrhage was equal in the two groups on postoperative days 3 and 7. In a clinical trial of 51 eyes undergoing diabetic vitrectomy, 70% of eyes randomized to air-filled vitreous cavity after vitrectomy had vitreous cavity hemorrhage on postoperative day 1 compared with 50% of fluid-filled eyes. At 1 week, the incidence of hemorrhage was 78% for air and 61% for fluid. The 6-month visual and anatomic results were similar in both groups. These findings suggest that an intravitreal air bubble neither improves hemostasis nor reduces the visual outcome after diabetic vitrectomy.     

Evaluation of the blood-aqueous barrier after vitreous replacement with perfluoropropane gas and liquid silicone.

Fluorophotometric measurements of blood-aqueous barrier permeability after intravitreal injection of perfluoropropane gas in rabbit eyes revealed fluorescein leakage immediately after injection; 3 days later, recovery of barrier integrity had begun to occur and 7 days and 14 days after gas injection, when the gas bubble was still in the eye, anterior chamber fluorescein concentrations were normal. Similarly, in eyes undergoing vitrectomy and injection of silicone liquid or vitrectomy only, anterior chamber fluorescein levels were elevated 3 days and 1 week after surgery. Nevertheless, normal barrier integrity was reestablished in both the silicone-filled eyes and the vitrectomized eyes after 1 week. Since there was no difference between the group injected with silicone and the group that underwent vitrectomy only with respect to anterior chamber fluorescein concentration at any of the times studied, it is concluded that the temporary disruption of the blood-aqueous barrier is associated with the surgical procedure rather than the presence of silicone liquid in the vitreous cavity.     

Long-term effect on optic nerve of silicone oil tamponade in rabbits: histological and EDXA findings

PURPOSE: Side-effects after intravitreal use of silicone oil (SO) are not well defined and elucidated. The object of this study was to examine the influence and toxicity of SO on the optic nerve after vitrectomy with SO tamponade. METHODS: We injected medical grade SO and emulsified SO into rabbit eyes after gas-mediated vitreous compression and examined the eyes by light microscopy (LM), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDXA) (point analysis and area analysis) 6 months after injection. We compared the findings in the non-treated eyes and eyes with only gas-mediated vitreous compression with those in SO-injected eyes. RESULTS: Vacuole-like structures were seen in the optic nerve posterior to the lamina cribrosa. In the group treated with only gas-mediated vitreous compression, the myelin structures were shown by TEM to be destroyed and replaced by glial tissue, while in groups injected with medical grade or emulsified SO severe destruction of the myelin sheath (myelinolysis) was observed. Silicone was identified at the electron-dense edges of the vacuoles by EDXA point analysis, but not in the vacuoles without electron-dense deposits. Dots of Si K alpha were not seen in the control groups, and dense dots were observed in SO-injected groups, by EDXA area analysis. CONCLUSIONS: Some of the vacuoles might be artefacts caused by insufficient fixation or the operative procedure, but TEM showed almost no artefacts in the control optic nerve. Thus, most vacuoles may be SO storage sites. SO uptake into the optic nerve might play a role in the pathogenesis of optic nerve atrophy after SO injection.