Evaluation of potential retinal toxicity of adalimumab (Humira)

Purpose  The purpose of this study is to evaluate the retinal toxicity of two doses of adalimumab (Humira), a recombinant human IgG1 monoclonal antibody specific for human tumor necrosis factor (TNF), when injected intravitreally in rabbits. Methods  Sixteen male pigmented rabbits (divided into two groups, eight animals per group) were used for this study. Two concentrations of adalimumab were tested: 0.5 mg/0.1 ml and 5 mg/0.1 ml. Each concentration was injected intravitreally randomly in one eye (study group) of each rabbit (group I received 0.5 mg/0.1 ml and group II received 5.0 mg/0.1 ml), while in the other eye (control group) 0.1 ml of sterile balanced saline solution (BSS) was injected. Slit-lamp and funduscopic examinations were performed every second day for 2 weeks for signs of infection, inflammation and toxicity. A baseline electroretinogram (ERG) was performed before the experiment and at the last follow-up day (day 14). ERG examination followed ISCEV standards. At the last follow-up day, the animals were sacrificed and the enucleated eyes were prepared for histological evaluation of retinal toxicity. Results  No differences in ERG responses at photopic and scotopic conditions were observed in eyes injected with either concentration of adalimumab or BSS. Furthermore, histologic examination of the retina in the enucleated eyes (in all groups) did not demonstrate any evidence of drug toxicity. Conclusions  Intravitreal adalimumab did not appear toxic to the retina in this experimental model at concentrations of 0.5 and 5 mg. If found safe in additional studies, intravitreally injected adalimumab could be evaluated for efficacy in the treatment of inflammatory eye conditions.     

Testing intravitreal toxicity of bevacizumab (Avastin)

PURPOSE: To evaluate the retinal toxicity of varying doses of bevacizumab when injected intravitreally in rabbits. Bevacizumab has been approved by the US Food and Drug Administration for the treatment of metastatic colorectal cancer. MATERIALS AND METHODS: Twelve New Zealand albino rabbits were used for this study and divided into four groups. Four concentrations of bevacizumab were prepared: 500 microg/0.1 mL, 1.0 mg/0.1 mL, 2.5 mg/0.1 mL, and 5.0 mg/0.2 mL. Each concentration was injected intravitreally in one eye of each of three rabbits; 0.1 mL volume of sterile balanced saline solution was injected into the contralateral eyes. Slit-lamp and funduscopic examinations were performed and the animals were observed for 2 weeks for signs of infection, inflammation, or toxicity. A baseline electroretinogram (ERG) was performed before the drug treatment and at day 14 before the animals were killed. The enucleated eyes were prepared for histologic evaluation of retinal toxicity. RESULTS: Histologic and ERG results in all groups showed no retinal toxicity. However, some inflammatory cells were found in the vitreous at the 5-mg dose. CONCLUSIONS: Intravitreal bevacizumab did not appear toxic to the retina in albino rabbits at a concentration of 2.5 mg. Intravitreally injected bevacizumab should be evaluated for efficacy in choroidal neovascularization and macular edema.     

纤溶酶和透明质酸酶诱导猪玻璃体后脱离的实验研究

目的研究纤溶酶和透明质酸酶诱导猪玻璃体后脱离(PVD)的有效性和安全性,比较两种酶单独应用和联合应用的效果。方法15只小型猪随机分为A、B、C三组,每组5只,随机选取一只眼为实验眼,对侧眼为对照眼,A组实验眼玻璃体腔注射50U/0.1ml透明质酸酶,B组实验眼注射0.5U/0.1ml纤溶酶,C组实验眼注射0.5U/0.05ml纤溶酶和50U/0.05ml透明质酸酶,对照眼均注射平衡盐溶液(BSS)0.1ml。注药后进行裂隙灯、直、间接检眼镜、眼B超、视网膜电图(ERG)等检查,7d后摘除眼球进行光镜、透射电镜、扫描电镜检查。结果B超检查显示A组有一只实验眼、B组有两只实验眼于注药后1d观察到部分性PVD,C组有一只实验眼于注药后1h观察到部分性PVD。B超、光镜和扫描电镜检查显示注药后7dA组和B组实验眼均见部分性PVD,C组实验眼均见完全性PVD,对照眼未见PVD。实验及对照眼注药前、后ERGa波、b波波幅均无显著性差异,光镜及透射电镜检查未见视网膜损害。结论0.5U纤溶酶和50U透明质酸酶单独及联合应用均可快速、安全、有效地诱导猪眼玻璃体后脱离,且联合用药较单独用药诱导PVD更快速、更有效。     

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.     

Safety of in vivo pharmacologic vitreolysis with recombinant microplasmin in rabbit eyes

PURPOSE: To investigate the safety of intravitreal microplasmin in rabbits and to confirm previous findings of posterior vitreous detachment (PVD). METHODS: Different doses of microplasmin, from 12.5 microg to 250 microg, in 0.1 mL balanced salt solution (BSS) were injected into the vitreous cavity of rabbit eyes to induce PVD. Fellow eyes were injected with the same volume of BSS. Slit-lamp biomicroscopy, ophthalmoscopic fundus examinations, A- and B-mode ultrasonography, and electroretinography were performed to assess the retina. Electroretinograms (ERGs) were recorded up to 90 days after injection. Morphologic alterations were assessed by light microscopy, scanning electron microscopy (SEM), and transmission (TEM) electron microscopy. RESULTS: A slight aqueous flare and cells were observed in the anterior chamber after microplasmin and BSS injection. A slight inflammatory reaction was also observed transiently in the vitreous cavity. In control eyes, B-mode ultrasonography and SEM examination demonstrated that PVD did not develop after BSS injection. Intravitreal injections of 125 microg or greater of microplasmin induced complete PVD with an internal limiting membrane (ILM) devoid of vitreous collagen fibrils. Eyes injected with 12.5 microg microplasmin had partial PVD, and SEM showed residual fibrils covering the ILM. In all eyes, there was a transient reduction in the a- and b-waves of the ERG on days 2 through 7. The ERGs showed less effect with < 250 microg microplasmin. CONCLUSIONS: Intravitreal injection of recombinant microplasmin in the rabbit induces no ERG or retinal ultrastructural abnormalities. Pharmacologic vitreolysis with this agent may be a useful adjunct to vitreous surgery and could be used to induce PVD without vitreous surgery.     

Investigation of the retinal biocompatibility of acid violet for chromovitrectomy

Purpose

The primary objective was to investigate the retinal biocompatibility of acid violet (AV) as a vital dye for chromovitrectomy. The secondary objective was to evaluate the capacity of AV to stain the anterior capsule of the lens.

Methods

An amount of 0.05 ml of 0.25 g/l and 0.5 g/l AV was injected intravitreally in the OD, while balanced salt solution (BSS) was applied in the OS for control. Clinical examination and histology with light microscopy (LM) were performed after 7 days. Retinal cell layers were evaluated for morphologic alterations and number of cells. The electroretinographic (ERG) changes were assessed at baseline and 7 days. In another part of the study, 0.1 ml of 0.25 g/l AV was injected into the anterior chamber of ex-vivo porcine eyes, and its capacity to stain the anterior capsule was determined. Cadaveric eyes were used to test the capacity of AV to stain the internal limitant membrane (ILM) during vitrectomy.

Results

The gross histopathologic appearance of the retina, choroids, sclera, and optic nerve was within normal limits, without any signs of severe retinal necrosis or cystic degeneration. AV caused no substantial retinal alterations in retinal layers by LM at either the lower or higher dose when compared with the control eye. The injection of AV did not induce considerable ERG alterations. The violet dye stained the anterior capsule after anterior chamber injection and the ILM, allowing a safer capsulorrhexis and vitrectomy.

Conclusion

Acid violet may be safe for the retina at concentrations of 0.25 and 0.50 g/l after intravitreous injection, and may be used as a vital dye for staining the anterior capsule and the ILM.     

粉防己碱抑制激光诱导鼠脉络膜新生血管

目的 观察玻璃体腔注射粉防己碱对实验性鼠脉络膜新生血管的抑制作用及其对视网膜结构和功能的影响。 方法 应用半导体激光（波长810 nm，曝光时间0.1 s，光斑直径100 μm，能量120 mW）光凝诱导20只Brown Norway (BN) 大鼠20只眼的脉络膜新生血管(CNV)模型。将大鼠随机分为实验组和对照组，每组各10只大鼠20只眼，实验组大鼠激光光凝后0、3 d玻璃体注射0.05 ml浓度为3.21 μmol/L的粉防己碱药液，对照组玻璃体内注射同体积的生理盐水；两组均在激光光凝14 d后行荧光素眼底血管造影，观察其新生血管的发生率。另有5只健康BN大鼠，每只鼠右眼玻璃体内注射入0.05 ml浓度为3.21 μmol/L的粉防己碱药液，左眼注射同体积生理盐水，第一次注药前及注药后1 h、1 d和第二次注药后1 h、1、7、14 d行视网膜电图（ERG）检查，第二次注药后14 d行光学、电子显微镜检查。 结果 实验组大鼠CNV发生率为23.26%，明显低于对照组63.33%（P<0.01）。3.21 μmol/L的粉防己碱玻璃体内注射b波波幅比率与注药前相比差异无统计学意义(P>0.05)。光学、电子显微镜检查未见明显细胞异常。 结论 粉防己碱能抑制鼠CNV形成；3.21 μmol/L浓度的粉防己碱玻璃体内注射对视网膜无毒性作用。 (中华眼底病杂志, 2006, 22, 242-244)     

Safety of intravitreal ketorolac and diclofenac: an electroretinographic and histopathologic study

OBJECTIVE: To determine the clinical, histologic, and electroretinographic effects in the rabbit retina of escalating doses of two intravitreally delivered nonsteroidal anti-inflammatory drugs (NSAIDs): ketorolac and diclofenac. METHODS: Right eyes received a single 0.1 mL injection of either ketorolac (500-6000 microg/0.1 mL) or diclofenac (300-1500 microg/0.1 mL) prepared in balanced salt solution (BSS). Left eyes served as controls and received BSS. Dark- and light-adapted electroretinograms (ERG) were obtained at baseline and 4 and 8 weeks postinjection. Enucleated eyes were examined histologically. RESULTS: Ophthalmic examinations demonstrated no signs of intraocular inflammation or retinal toxicity. Intraocular pressure measurements remained similar between NSAID injected and control eyes. Histologic and ERG studies of eyes injected with 6000 microg ketorolac and >or=500 microg diclofenac demonstrated toxicity. In contrast, doses up to 3000 microg ketorolac demonstrated enhanced b-wave amplitude responses. Delayed drug toxicity was observed for the highest doses of both NSAIDs. CONCLUSIONS: Intravitreal 3000 microg ketorolac and 300 microg diclofenac were nontoxic in this animal study, and may offer an effective and safer alternative to intravitreal corticosteroids.     

Safety and efficacy of dispase and plasmin in pharmacologic vitreolysis

PURPOSE: To evaluate the safety and efficacy of dispase and plasmin when inducing posterior vitreous detachment (PVD) by intravitreous injection in rabbit eyes. METHODS: Forty-eight young pigmented rabbits were randomized into six groups. Groups 1 and 5 received 0.025 U dispase in test eyes; group 2, 0.1 U dispase; groups 3 and 6, 1 U plasmin; and group 4, 4 U plasmin. All groups received PBS in control eyes. Groups 5 and 6 were euthanatized 15 minutes after surgery for ocular histologic examination. The remaining groups (groups 1-4) received indirect ophthalmoscope and biomicroscopy 15 and 30 minutes; 1, 2, and 8 hours; and 1, 3, and 7 days after surgery. Ultrasonography and electroretinogram were performed 1 hour and 1 and 7 days after surgery. The eyes then were examined by scanning and transmission electron microscopy. RESULTS: Partial or complete PVDs were observed in the eyes that received dispase and plasmin, confirmed by the results of scanning electron microscopy. Light microscopy showed inflammation in both dispase- and plasmin-treated eyes of groups 5 and 6. However, whereas in plasmin-treated eyes the ERG and cell ultrastructure showed no significant changes, in dispase-treated eyes, the amplitudes of ERG showed a significant reduction from baseline and ultrastructural damage to the retina was detected by transmission electron microscopy. Cell damage, preretinal hemorrhage, and cataract were also observed in these eyes. No changes were observed in the control eyes. CONCLUSIONS: Intravitreal injection of dispase at 0.025 U or more can induce PVD, but it is not safe. Plasmin (1-4 U) is safer, except for the potential risk of inducing intraocular inflammation.     

Safety of repeated intravitreous injections of antibiotics and dexamethasone

PURPOSE: To determine the retinotoxicity of repeated intravitreous injections of vancomycin, ceftazidime, and dexamethasone in rabbit eyes. METHODS: Twenty pigmented New Zealand rabbits were divided into two groups. In Group 1, the right eyes received repeated intravitreous injections with vancomycin 0.3 mg, ceftazidime 0.7 mg, and dexamethasone sodium phosphate 0.13 mg at three consecutive 48-hour intervals. Group 2 right eyes received three times higher dose of the same intravitreous drugs as used in Group 1, repeated at the same frequency. All left eyes served as control eyes. Retinotoxicity was monitored by slit-lamp biomicroscopy, indirect ophthalmoscopy, electroretinography, and light and electron microscopy. RESULTS: No evidence of retinotoxicity was found in Group 1 eyes. Photopic A-waves were significantly elevated, and 30- and 50-Hz flicker fusion amplitudes were significantly depressed in Group 2 eyes. No changes were found by clinical or histopathologic examination in the retinas of either group. CONCLUSIONS: Three repeated intravitreous injections at 48-hour intervals of a combination of vancomycin, ceftazidime, and dexamethasone in rabbit eyes at dosages that approximate drug concentrations recommended for human endophthalmitis were nontoxic. Similar injections at three times higher doses resulted in mild electroretinogram changes.