Intravitreal acetylsalicylic acid in silicone oil: pharmacokinetics and evaluation of its safety by ERG and histology

BACKGROUND: A new method of intravitreal drug delivery of acetylsalicyclic acid (AS) in silicone oil was investigated for safety and for its pharmacokinetics in the posterior pole of the eye. METHODS: The AS was mixed in silicone oil to a concentration of 1.67 mg/ml. After vitrectomy, 15 NZW rabbits received an intravitreal injection of AS/silicone oil suspension. Clinical examination, pre- and postoperative electroretinography (ERG) and histology were performed. The pharmacokinetics of the distribution of salicylic acid was determined by HPLC analysis at 6 h, 24 h and 5 days in optic nerve, retina, choroid, vitreous, and blood. RESULTS: Clinical examination and histology revealed no adverse effects or signs of toxicity. The ERGs showed no significant difference between the pre- and postoperative results. The salicylic acid concentrations demonstrated peak values in the residual vitreous (640.0 micrograms/ml), choroid (446.0 ng/mg) and retina (281.3 ng/mg) at 6 h. At 24 h, the salicylic acid concentration decreased to 20.9 micrograms/ml in the residual vitreous and to 38.5 ng/mg in the retina. At 5 days the retinal level was still 48.1 ng/mg. CONCLUSIONS: AS delivery by intravitreal administration of loaded silicone oil is a safe method and results in high concentrations of salicylic acid in the posterior segment of the eye while maintaining low blood levels.     

Intraocular properties of urokinase-derived antiangiogenic A6 peptide in rabbits.

To investigate the intraocular properties of an antiangiogenic peptide, A6, a total of 70 New Zealand rabbit eyes were used. For the toxicity study, 0.05 mL of 0.459 M or 0.148 M A6 was injected intravitreally; right eyes received A6, and left eyes received a vehicle. Serial intraocular pressure measurement, slit lamp, and indirect ophthalmoscopy were performed. The rabbit eyes were evaluated by fluorescein angiography, electroretinography, and histology after the scheduled sacrifice. The pharmacokinetics of an intravitreal A6 (0.05 mL of 0.488 M) and a subtenon A6 (0.5 mL of 0.305 M) injection was studied. There was no toxicity observed following the 0.148 M A6 intravitreal injections. In 2 eyes with a 0.459 M A6 intravitreal injection, focal retinal pigmentary change was observed at the injection site, which was contacted by the hyperosmolar drug bolus. Choroidal A6, following the intravitreal injection, remained therapeutic (>or=10 microM) for 72 hours. The vitreous half-life was 19.4 hours. Choroidal concentrations following the subtenon injection were minimal. The low choroidal concentrations observed may relate to the polar nature of A6. More hydrophobic analogs of A6 are likely to cross the retina more efficiently. However, in diseased eyes, in the area of choroidal neovascularization (CNV), the fluid-filled, damaged, edematous retina may permit the drug to enter the choroid in higher concentrations.     

Pharmacokinetics of intraocular drug delivery by periocular injections using ocular fluorophotometry

PURPOSE: To evaluate the pharmacokinetics of the periocular injections: posterior subtenon (PST), retrobulbar (RB), and subconjunctival (SC) injection. METHODS: Two sodium fluorescein (NaF) concentrations, 2.5 mg in 0.1 mL (NaF1) and 2.5 mg in 0.5 mL (NaF2) were injected into live rabbits by the PST (NaF1 n = 4, NaF2 n = 3), RB (NaF1 n = 10), SC (NaF1 n = 6), and intravenous (IV, NaF1 n = 6) routes and into euthanatized rabbits by the RB (NaF1 n = 8) route. NaF concentrations in the choroid/retina, vitreous, and anterior segment were measured by ocular fluorophotometry. The NaF level in the contralateral choroid/retina was used as a measure of the systemic drug levels. RESULTS: The maximum NaF concentrations (nanograms per milliliter) in the choroid/retina after PST, RB, SC, and IV were 757 +/- 549 at 2 hours, 906 +/- 1014 at 1 hour, 320 +/- 462 at 2 hours, and 865 +/- 363 at 5 to 10 minutes, respectively. The PST had the highest and most prolonged vitreous NaF1 concentration (maximum: 270 +/- 226 ng/mL at 3.5 hours). The contralateral peak choroid/retina NaF levels after the RB, SC, and IV injections were 7, 4, and 21 times greater than after the PST injection. The SC injection had the highest anterior segment NaF concentration (5364 +/- 2840 ng/mL at 2 hours). PST with NaF2 resulted in intraocular NaF levels higher than with NaF1. CONCLUSIONS: NaF reaches the choroid/retina by transscleral diffusion from the periocular depot. The orbital and conjunctival vasculature and lymphatics have a larger role in NaF clearance than does the choroid. NaF diffuses into the vitreous from the choroid and the anterior segment; the periocular depot location determines the predominant diffusion pathway. The duration of high NaF levels in the choroid/retina or the anterior segment determines vitreous NaF levels. PST is the best periocular route for vitreous NaF delivery with minimal systemic levels. Increasing the volume of NaF PST depot enhances transscleral drug delivery.     

Evaluation of intraocular pharmacokinetics and toxicity of prinomastat (AG3340) in the rabbit.

To determine the ocular pharmacokinetics, physiological and histological effects of prinomastat (a matrix metalloprotease inhibitor), a total of seventy-seven eyes of New Zealand White rabbits received intravitreous and subtenon injections of prinomastat or of acidified water vehicle as control, Doses of 0.5 mg in 0.05 mL of prinomastat or acidified water were used for intravitreal injection. For the subtenon injections, doses of 5 mg prinomastat in 0.5 mL of acidified water were administered in the superotemporal quadrant. Intraocular pharmacokinetics were determined by analyzing vitreous samples at different postinjection time points using Liquid Chromatography-Mass Spectroscopy/Mass Spectroscopy (LC-MS/MS). The toxicity was evaluated by biomicroscopy, electroretinography (ERG), pneumatonometry, and histology. No toxicity was found with either administration method. At day 14 after intravitreal injection, levels of prinomastat in the vitreous and choroid were 1.4 ng/mg and 7.8 ng/mg, respectively. The retinal levels of prinomastat were 22 ng/mg at 24 hr and dropped below 1 ng/mg at 48 hr. Prinomastat remained well above minimum effective concentration in the choroid for at least four weeks after a single intravitreal injection, suggesting that local intravitreal injection may have potential in treating choroidal neovascularization.     

Penetration of bevacizumab through the retina after intravitreal injection in the monkey

PURPOSE: The penetration of intravitreally injected bevacizumab in its commercial formulation (Avastin; Roche, Grenzach, Germany) through the retina was studied, to determine whether a full-length antibody would be able to penetrate the retina as easily as an antibody fragment. METHODS: Six cynomolgus monkeys (Macaca fascicularis) were used in this study. Two compositions of intravitreal injection into the right eyes were performed: one with commercial Avastin (group 1, four animals) and the other one with commercial Avastin labeled with 125I (group 2, one animal). The animals in group 1 were killed 1, 4, 7, or 14 days after the injection for subsequent histologic analysis of the eyes by immunohistochemistry, and the animal in group 2 was killed 7 days after injection for autoradiography and electron microscopy. Funduscopy was performed before the injection and at several time points thereafter. Moreover, blood samples were collected at different time points from the group-2 animal. The sixth animal remained untreated and served as the control. RESULTS: No pathologic changes were obvious in the funduscopic images within the time of the experiment. Bevacizumab immunoreactivity was found in the choroid and the inner layers of the retina as early as 1 day after the injection and spread to the outer layers and the choroid within the following days, in particular to photoreceptors and blood vessels. Avastin labeled with 125I showed radioactivity in blood serum 1 day after the intravitreal injection and remained relatively stable until day 7. CONCLUSIONS: The results clearly show that the bevacizumab molecule can penetrate the retina and is also transported into the retinal pigment epithelium, the choroid and, in particular, into photoreceptor outer segments after intravitreal injection of Avastin. Active transport mechanisms seem to be involved.     

Pharmacokinetics of a long-lasting anti-VEGF fusion protein in rabbit

Conbercept(KH902), a recombinant fusion protein in clinical trial II/III, shows good potential to treat the neovascular age-related macular degeneration (AMD). This investigation evaluated its ocular pharmacokinetics and pharmacodynamic profile in rabbits following intravitreal administration (IVT). Rabbits (n = 120) received single bilateral conbercept IVT administration or single IV administration. Conbercept concentrations in ocular tissues and serum were measured after dosing. VEGF concentration was also measured simultaneously. The results showed that conbercept rapidly distributed from vitreous into targeted tissues and lasted over 81 days. Clearance in ocular tissues was parallel and exhibited a terminal half of 2.5-4.2 days. The drug exposure in the retina was 1/4 to 1/5 of that in vitreous. Serum conbercept concentrations after IVT dosing were low and bioavailability was approximately 44%. And single intravitreal injection induced that ocular VEGF concentration declined over 60 days and serum VEGF concentration decreased for a short time but rebounded to higher level than baseline later. All these indicated conbercept good pharmacokinetic profile in rabbits, with good ocular tropism and systemic tolerance. Combined with the efficacy data from our earlier in vitro and in vivo studies, it should have a promising clinical application for AMD treatment.     

琥珀酸甲泼尼龙兔眼球周注射的药代动力学研究

目的：检测琥珀酸甲泼尼龙(methylprednisolone sodium succinate,MPS)兔眼球周注射后,MPS和其在眼内的代谢产物甲泼尼龙(methylprednisolone,MP)的分布及药代动力学情况。

方法：兔眼球周注射琥珀酸甲泼尼龙钠10mg,采用质谱-液相色谱方法检测MPS和MP在巩膜、脉络膜和视网膜、玻璃体、虹膜、房水、晶状体、视神经和血浆中的浓度。

结果：球周注射琥珀酸甲泼尼龙钠后, MPS浓度在眼内组织中的达峰时间为注药后0.25～1h,在血浆中的达峰时间为注药后0.25h; MP浓度在眼内组织中的达峰时间为0.5～6h,在血浆中的达峰时间为注药后0.5h。MPS和MP在眼内各组织的达峰浓度由高到低依次为巩膜、视神经、脉络膜和视网膜、虹膜、晶状体,二者在晶状体内的浓度均为所有眼部组织中最低,且远远低于眼内其它组织的含量,但平均驻留时间最长。

结论：球周注射MPS是一种有效的向眼组织传递药物的方式,且该药在眼内的分布有利于向巩膜、视神经和脉络膜视网膜给药,而不易被晶状体吸收。     

Intravitreal toxicity of high-dose etanercept.

PURPOSE: The aim of this study was to evaluate the retinal toxicity of high-dose intravitreal etanercept, a U.S. Food and Drug Administration-approved anti-inflammatory drug, in the rabbit model. METHODS: Twenty (20) New Zealand albino rabbits were divided into 5 groups (n=4); eyes in each group were intravitreally injected with one of the following doses of etanercept: 125 microg, 250 microg, 500 microg, 1 mg, or 2.5 mg. One (1) eye in each animal was used for the study dose; the fellow eye was injected with buffered sterile saline as a control. All animals were examined using indirect ophthalmoscopy and slit-lamp biomicroscopy before and after intravitreal injection and at days 1, 7, and 14. Electroretinography (ERG) was performed on all animals before intravitreal injection and 14 days after injection. The animals were euthanized on day 14. Histological preparations of the enucleated eyes were examined with light microscopy for retinal toxicity. RESULTS: Clinical examination, histological evaluation, and ERG results of all 5 groups demonstrated no signs of retinal toxicity. CONCLUSIONS: Intravitreal doses as high as 2.5 mg of etanercept did not cause retinal toxicity. Intravitreal doses of up to 2.5 mg of etanercept may provide a more potent, prolonged effect than the lower doses previously recommended.     

Modeling of corneal and retinal pharmacokinetics after periocular drug administration

PURPOSE: To develop pharmacokinetics models to describe the disposition of small lipophilic molecules in the cornea and retina after periocular (subconjunctival or posterior subconjunctival) administration. METHODS: Compartmental pharmacokinetics analysis was performed on the corneal and retinal data obtained after periocular administration of 3 mg of celecoxib (a selective COX-2 inhibitor) to Brown Norway (BN) rats. Berkeley Madonna, a differential and difference equation-based modeling software, was used for the pharmacokinetics modeling. The data were fit to different compartment models with first-order input and disposition, and the best fit was selected on the basis of coefficient of regression and Akaike information criteria (AIC). The models were validated by using the celecoxib data from a prior study in Sprague-Dawley (SD) rats. The corneal model was also fit to the corneal data for prednisolone at a dose of 2.61 mg in albino rabbits, and the model was validated at two other doses of prednisolone (0.261 and 26.1 mg) in these rabbits. Model simulations were performed with the finalized model to understand the effect of formulation on corneal and retinal pharmacokinetics after periocular administration. RESULTS: Celecoxib kinetics in the BN rat cornea can be described by a two-compartment (periocular space and cornea, with a dissolution step for periocular formulation) model, with parallel elimination from the cornea and the periocular space. The inclusion of a distribution compartment or a dissolution step for celecoxib suspension did not lead to an overall improvement in the corneal data fit compared with the two-compartment model. The more important parameter for enhanced fit and explaining the apparent lack of an increase phase in the corneal levels is the inclusion of the initial leak-back of the dose from the periocular space into the precorneal area. The predicted celecoxib concentrations from this model also showed very good correlation (r = 0.99) with the observed values in the SD rat corneas. Similar pharmacokinetics models explain drug delivery to the cornea in rat and rabbit animal models. Retinal pharmacokinetics after periocular drug administration can be explained with a four-compartment (periocular space, choroid-containing transfer compartment, retina, and distribution compartment) model with elimination from the periocular space, retina, and choroid compartment. Inclusion of a dissolution-release step before the drug is available for absorption or elimination better explains retinal t(max). Good fits were obtained in both the BN (r = 0.99) and SD (r = 0.99) rats for retinal celecoxib using the same model; however, the parameter estimates differed. CONCLUSIONS: Corneal and retinal pharmacokinetics of small lipophilic molecules after periocular administration can be described by compartment models. The modeling analysis shows that (1) leak-back from the site of administration most likely contributes to the apparent lack of an increase phase in corneal concentrations; (2) elimination via the conjunctival or periocular blood and lymphatic systems contributes significantly to drug clearance after periocular injection; (3) corneal pharmacokinetics of small lipophilic molecules can be explained by using similar models in rats and rabbits; and (4) although there are differences in some retinal pharmacokinetics parameters between the pigmented and nonpigmented rats, the physiological basis of these differences has yet to be ascertained.     

Tolerability and pharmacokinetics of intravitreal sirolimus

Abstract Purpose: To evaluate the pharmacokinetics (PK) and tolerability of a proprietary sirolimus depot-forming ocular formulation in rabbits and humans after a single intravitreal (IVT) injection. Methods: New Zealand White (NZW) rabbits were intravitreally injected in both eyes with an injectable formulation in 5 (3 PK and 2 tolerability) studies. The rabbits received up to approximately 220?μg sirolimus per eye. At the desired timing post-injection, the animals were euthanized; both eyes were enucleated, frozen, and dissected to separate sclera, retina/choroid, and vitreous humor (VH). Whole blood (WB) samples were obtained at each time point before euthanasia. In clinical trials, patients received an IVT injection of approximately 352?μg sirolimus. Sirolimus concentrations in ocular tissues and WB samples were measured using liquid chromatography/tandem mass spectrometry (LC/MS/MS). In both single- and repeat-dose tolerability studies, systemic and ocular adverse effects were evaluated. Results: After IVT administration, sirolimus formed a depot in the VH. During dissolution, concentrations in VH were dose related and exhibited continuous release from the depot. This was characterized by a gradient of sirolimus concentration in the order of VH > retina/choroid > sclera > WB, and the concentrations were maintained for approximately 2 months after the IVT injection. After repeat dosing (132?μg), no drug accumulation was seen in the ocular tissue or systemically. In clinical studies, the highest blood levels were <2?ng/mL at day 2, and half-time (t(1/2)) was 8-9 days. There was no accumulation at day 30 after the IVT injection (up to 352?μg). Safety studies conducted on rabbits indicated good local tolerability. Sirolimus-related effects were limited to minor incipient cataract findings and mild lenticular changes. In the clinical studies where sirolimus was intravitreally administered up to 352?μg, injections were well tolerated. Conclusions: Sustained IVT delivery was achieved in a dose-dependent fashion after the IVT injection of a proprietary sirolimus depot-forming ocular formulation. Across the tolerability and safety studies, no significant findings were observed for systemic and ocular tolerability. The human WB levels were well below the daily trough systemic blood level range required for systemic immunosuppression. An IVT injection of sirolimus has a PK and safety profile that is favorable for treating inflammatory conditions of the eye, such as non-infectious uveitis, and warrants further investigation in humans.     

Intravitreal pharmacokinetics of plain and liposome-entrapped fluconazole in rabbit eyes.

The objective of our experiment was to study the pharmacokinetics of plain and liposome-encapsulated fluconazole after an intravitreal injection (100 microg/0.1 ml) in rabbit eyes. Equal concentrations of plain and liposome-entrapped fluconazole were injected intravitreally into albino rabbits through the pars plana after intravenous pentobarbitone anesthesia. The rabbits were sacrificed at various time intervals, and the concentration of fluconazole in vitreous, retina-choroid, aqueous humor and cornea was estimated using High Performance Liquid Chromatography (HPLC). Plain fluconazole showed a rapid vitreal clearance and a short half-life (3.08 hr), whereas liposome-entrapped fluconazole showed a longer half-life (23.40 hr). The terminal elimination constant (Ke) of the liposome-loaded drug from the vitreous was seven times less than the plain drug. In the plain fluconazole group, at 1 hr, a high concentration of the drug was found in the retina. To conclude, the elimination of fluconazole was primarily transretinal and was very rapid. Liposome encapsulation significantly increased the half-life of fluconazole in the vitreous cavity.     

神经营养因子促进视神经夹伤后视网膜生长相关蛋白-43表达

目的：观察大鼠视神经夹伤后视网膜的神经生长相关蛋白－43（growth associated protein-43,GAP-43)的表达变化及胰状神经营养因子（ciliary neurotrophic factor CNTF)和腺病毒介导脑源性神经营养因子（adenovirally delivered brain-derived neurotrophic factor,Ad-BDNF)对视神经夹伤的保护作用。方法：在眼球后2mm处作视神经夹伤，制作SD大鼠视神经夹伤模型，通过巩膜进行玻璃体微量注射神经营养因子（neurotraphic factors,NFs)，应用免疫印迹法观察视网膜的GAP－43表达量的变化。结果：正常SD大鼠视网膜上GAP－43呈现低表达，分子量约为46．7ku；玻璃体注射CNTF，大鼠视神经夹伤后2周，GAP－43的表达增强（P＜0．05），玻璃体注射Ad-BDNF，在视神经夹伤后4周内GAP－43的表达增强（P＜0．05），但这种作用以视神经损伤后1周时最为明显。结论：玻璃体注射NFs能够在一定时间范围内促进神经夹伤的SD大鼠视网膜上GAP－43表达，其中Ad-BDNF的促进作用能够维持相对较长的时间。     

豚鼠形觉剥夺超高度近视模型的形态学研究

目的建立豚鼠形觉剥夺超高度近视模型并观察其后极部各层组织的病理组织学变化。方法 2周龄三色豚鼠分为形觉剥夺组（12只）和非形觉剥夺对照组（8只）,于形觉剥夺前,形觉剥夺后4、6、10、14周分别对各组进行检影和眼轴性参数测量。通过病理组织学光镜检查分析形觉剥夺14周后各组视网膜、脉络膜和巩膜厚度及其形态学的变化。结果豚鼠形觉剥夺后随时间延长近视度数逐渐增高,10周后可达-10.00 D以上的超高度近视,14周后近视度数更高、个别个体可达-20.00 D。眼轴性参数相应延长。形觉剥夺超高度近视眼视网膜、脉络膜和巩膜较对照组均明显变薄并有病理性改变。结论应用遮盖法对豚鼠施行长期单眼形觉剥夺会形成超高度近视,10周后可达-10.00 D以上,超高度近视眼巩膜、脉络膜和视网膜明显变薄,脉络膜和巩膜结构发生紊乱。视网膜结构中感光细胞层变薄最为明显,推测其对超高度近视的发生起重要作用。     

Antiviral activity and ocular kinetics of antisense oligonucleotides designed to inhibit CMV replication

PURPOSE: To compare the antiviral activity and ocular distribution of first- and second-generation antisense oligonucleotides intended for the treatment of cytomegalovirus (CMV) retinitis. METHODS: The antiviral activity of ISIS 13312 and ISIS 2922 (Isis Pharmaceuticals, Inc., Carlsbad, CA) against 10 clinical CMV isolates was compared with a plaque-reduction assay. The ocular pharmacokinetics were compared after intravitreal injection in rabbits (36-90 microg) and monkeys (125-500 microg). Vitreous and/or retina were collected after single and multiple injections to characterize ocular distribution, clearance, and accumulation. Oligonucleotide concentrations were measured by capillary gel electrophoresis and immunohistochemical techniques. RESULTS: ISIS 13312 and ISIS 2922 demonstrated comparable antiviral activity that was consistent among the 10 clinical isolates examined (50% inhibitory concentration [IC(50)], <1 microM). Activity was independent of the resistance of CMV isolates to DNA polymerase inhibitors. After intravitreal injection, the kinetics of ISIS 2922 and ISIS 13312 were characterized by clearance from vitreous and distribution to the retina; however, ISIS 2922 was cleared more quickly from the retina than ISIS 13312. The half-life of ISIS 13312 in the monkey retina was approximately 2 months. Retinal concentrations of ISIS 13312 were dose dependent, with approximately a twofold increase in concentration after once-monthly doses compared with single-dose concentrations. Immunohistochemical analysis indicated that both oligonucleotides were efficiently distributed to numerous ocular tissues, including retina, ciliary body, and optic nerve. CONCLUSIONS: ISIS 13312 possesses antiviral activity and pharmacokinetic properties that favor its use as a therapeutic agent in treatment of CMV retinitis. The half-life of ISIS 13312 in retina is longer than that of ISIS 2922, potentially allowing for less frequent administration.     

Effects of photodynamic therapy using verteporfin on experimental choroidal neovascularization and normal retina and choroid up to 7 weeks after treatment.

PURPOSE: To study the long-term effects of photodynamic therapy (PDT), using liposomal benzoporphyrin derivative (BPD) or Verteporfin, on experimental choroidal neovascularization (CNV) and on normal retina and choroid (with no CNV) in the cynomolgus monkey eye. METHODS: Photodynamic therapy was performed in 8 cynomolgus monkey eyes with experimental CNV induced by laser injury. The effect of PDT on normal retina and choroid (with no CNV) was studied in 9 monkey eyes. Liposomal BPD was administered intravenously (0.375 mg/kg) either as a bolus, as a slow infusion over 32 minutes, or as a fast infusion over 10 minutes. Photodynamic therapy was performed using light at a wavelength of 689 or 692 nm, with an irradiance of 600 mW/cm2 and fluence of 150 J/cm2. Follow-up studies, including fundus photography and FA, were performed at 24 hours after PDT and then weekly. Indocyanine green and BPD angiography were performed in selected cases. Tissues were examined with light and electron microscopy at the end of follow-up. RESULTS: Twenty-three of the 32 areas of CNV treated with PDT showed absence of angiographic leakage at 24 hours. Twenty-eight areas of CNV were followed for 4 weeks; 22 of 28 showed absence of angiographic leakage at 2 weeks; and 20 of 28 at 4 weeks of follow-up. Forty spots on the normal retina and choroid were treated with PDT and were followed for 4 to 7 weeks. These spots showed pigment-laden cells in the outer retina, variably pigmented retinal pigment epithelium (RPE) in the treated area, intact neurosensory retina, and reperfusion of the choriocapillaris. CONCLUSIONS: Photodynamic therapy leads to absence of angiographic leakage for at least 4 weeks in experimental CNV in the monkey model. In the normal monkey eye the RPE and choriocapillaris show generalized recovery with preservation of the neurosensory retina 7 weeks after PDT.     

Histology of wound, vitreous, and retina in experimental posterior penetrating eye injury in the rhesus monkey.

We performed a histologic study to support our clinical observations on the mechanisms responsible for traction retinal detachment after a penetrating injury in the rhesus monkey eye. The monkey eyes (40 eyes; 40 monkeys) were characterized by intraocular fibrosis with the formation of a cyclitic membrane and epiretinal and subretinal membranes. The progression to a fibrous ingrowth from the wound occurred only in eyes with blood in the vitreous. The intravitreal fibroblastic proliferation had its origin mainly from the stroma of the ciliary body and choroid at the wound but probably also from the nonpigmented ciliary epithelium. A fibroblastic response was present within the vitreous as early as four days after injury, and had progressed to form a cyclitic membrane by six weeks. Epiretinal membranes were identified as early as four weeks after injury. They were most prominent over the peripheral retina anterior to the equator. It is likely that they are derived from multiple cellular sources including the fibrous ingrowth from the wound but they were also connected to the surface of the retina by bridges of tissue indicating a glial origin. The subretinal membranes appeared to be derived from both retinal pigment epithelium cells and glial cells.     

Safety and pharmokinetics of triamcinolone hexacetonide in rabbit eyes.

PURPOSE: The aim of this study was to evaluate whether intravitreal triamcinolone hexacetonide (TH) is a safe, longer lasting alternative to intravitreal triamcinolone acetonide (TA) in the rabbit eye. METHODS: Three groups, each comprising of 15 Dutch-belted rabbits, received a unilateral injection of 0.1 mL of drug and 0.1 mL of physiologic salt solution in the fellow eye. Group I received TA, group II received commercially available TH, and group III received reformulated iso-osmolar triamcinolone hexacetonide (rTH). Simultaneous bilateral dark-adapted electroretinography was performed following the injection. Retinal morphology was assessed by using histopathology in each group enucleated 12 weeks after injection. High-performance liquid chromatography of vitreous isolated from the enucleated eyes was used to determine drug concentrations. RESULTS: A significant reduction in saturated a-wave and maximal scotopic b-wave was observed in the group II eyes relative to the fellow control eyes at both 2 and 12 weeks postinjection (P < 0.001 for each comparison) but not in the other groups. Histopathology showed no differences between drug-injected eyes and fellow control eyes in groups I and III, but in group II there was severe degeneration of all retina layers. In group I, the drug half-life was 17.7 +/- 1.7 days, group II 44 +/- 13 days, and group III 12.8 +/- 2.3 days. CONCLUSIONS: The half-life of commercially available TH in the vitreous is double that of TA, but the former is toxic to the retina in this rabbit model. Reformulated iso-osmolar TH showed no evidence of deleterious effects to retina function or structure but had a similar half-life to TA.     

Determination of nontoxic concentrations of piperacillin/tazobactam for intravitreal application. An electroretinographic, histopathologic and morphometric analysis

BACKGROUND: To investigate the highest nontoxic intravitreal dose of piperacillin/tazobactam in rabbits. MATERIAL AND METHODS: Forty New Zealand white albino rabbits were used in this study. The rabbits were divided into four equal groups (10 rabbits in each) and the right eyes were treated with 0.1 ml intravitreal injections of 1,000 microg piperacillin/tazobactam in group 1, 500 microg in group 2, 250 microg in group 3, and 100 microg in group 4. The left eyes served as controls and were injected with 0.1 ml of saline solution. Ganzfeld electroretinogram (ERG) was performed on all eyes before and after 4 weeks of intravitreal injections. Then, the rabbits were killed and the eyes were enucleated for histopathological evaluation of the retina. Retinal sections were evaluated by morphometric analyses on cell counts of ganglion cell layer and thickness of the various retinal layers. RESULTS: Baseline ERGs were similar among the groups (p > 0.05). After 4 weeks of injection, there were a reduction of the b-wave amplitude and extension of the b-wave implicit time in photopic and scotopic ERGs in group 1 and group 2 when compared with controls (for each, p < 0.001). Intravitreal injection of 100 and 250 microg piperacillin/tazobactam did not cause any deterioration of the b-wave of ERGs throughout the follow-up period of 4 weeks (for each, p > 0.05). After morphometric analysis of retinal sections in all groups, there were no statistically significant differences in the mean number of surviving ganglion cells, thickness of the whole retina and the inner plexiform layer compared with controls (p > 0.05). CONCLUSION: 250 microg/0.1 ml piperacillin/tazobactam is the highest nontoxic dose to the normal retinas of adult albino rabbits as intravitreal injection. Piperacillin/tazobactam may be a new, potentially important drug in the treatment of endophthalmitis as it has a broad antimicrobial spectrum.     

Lokalisation von Bevacizumab in der Netzhaut von Affen nach einer intravitrealen Bevacizumab-Injektion

Background

The aim was to investigate to what extent the vascular endothelial growth factor (VEGF) antibody bevacizumab is able to penetrate the retina in primates after an intravitreal injection of Avastin.

Material and Methods

Monkeys (Macaca fascicularis) were injected intravitreally with radioactively labelled and free Avastin. The animals were sacrificed 1, 4, 7, or 14 days after the injection, and the eyes were examined histologically and immunohistochemically. Blood samples were also taken on several days.

Results

In the fundoscopic images, no pathologic changes could be found during the experiment. Using immunohistochemistry, bevacizumab was found in the choroid and the inner layers of the retina 1 day after the injection. Bevacizumab penetrated more quickly in the fovea than in the rest of the retina. It was also encountered in the photoreceptors and blood vessels. When ¹²⁵I-labelled Avastin was used, radioactivity could be determined in the blood serum 1 day after the injection.

Conclusion

The results show that the bevacizumab molecule can penetrate the retina after intravitreal injection of Avastin. However, there is an active uptake in the retinal cells.     

纤溶酶K区缺失突变体玻璃体腔注射对光化学诱导大鼠视网膜分支静脉阻塞的溶栓作用

背景 视网膜静脉阻塞是常见的视网膜血管性疾病,目前溶栓和抗凝疗法是重要的治疗手段.然而,系统溶栓疗法效率较低,且易增加出血风险. 目的 观察玻璃体腔注射纤溶酶K区缺失突变体(PLM-ΔK)对光化学诱导的大鼠视网膜分支静脉阻塞(BRVO)的治疗作用. 方法 用SD大鼠尾静脉注射孟加拉玫瑰红溶液40 mg/kg,然后用氩激光照射视网膜静脉法建立SD大鼠BRVO模型,采用随机数字表法将造模成功的40只大鼠随机分为平衡盐溶液(BSS)组、0.01U(商品单位)PLM-ΔK组、0.02 U PLM-ΔK组和0.03 UPLM-ΔK组,每组10只.造模并避光饲养大鼠12h后于大鼠玻璃体腔内分别注射BSS和0.01、0.02或0.03 UPLM-ΔK 10μl,各组大鼠于注射后3d行间接检眼镜、荧光素眼底血管造影(FFA)检查.用过量麻醉法处死SD大鼠并制备视网膜铺片和眼球壁切片,采用苏木精-伊红染色法观察大鼠球壁的形态学变化;采用免疫荧光法检测大鼠球壁组织中人纤连蛋白(FN)和层黏连蛋白(LN)的表达;透射电子显微镜下观察大鼠视网膜的超微结构改变.结果 玻璃体腔内药物注射后3d,FFA显示BSS组及0.01、0.02或0.03 U PLM-ΔK组视网膜分支静脉再通达2支以上的大鼠数量分别为0、3、6和8只,组间总体比较差异有统计学意义(x2=9.635,P=0.022),其中0.01 U PLM-ΔK组再通血管的大鼠数量与BSS组比较,差异无统计学意义(Z=-1.558,P=0.119),而0.03 U PLM-ΔK组再通血管的大鼠数量明显多于0.01 U PLM-ΔK组,差异有统计学意义(Z=-2.762,P=0.006).玻璃体腔药物注射后3d,BSS组大鼠视网膜静脉内可见血栓形成,视网膜铺片可见新生血管;而0.03 U PLM-ΔK组可见大鼠玻璃体后脱离,视网膜铺片未见新生血管形成.BSS组可见FN主要表达于内界膜(ILM)层、感光细胞层(PCL)、外界膜(OLM)层、脉络膜和巩膜,LN主要表达于大鼠ILM层、OLM层和巩膜,且均呈强表达.0.03 U PLM-ΔK组大鼠球壁各层组织中FN荧光强度较BSS组明显减弱,脉络膜层FN表达接近消失,LN在ILM层表达增强,而OLM层和巩膜表达减弱.结论 玻璃体腔注射PLM-ΔK促进阻塞的视网膜分支静脉再通,是潜在的BRVO治疗药物.PLM-ΔK玻璃体腔注射后可以扩散至脉络膜并降解FN和LN.