Safety threshold of intravitreal activated protein-C.

PURPOSE: Although activated protein C (APC) is effective in preventing the death of retinal neurons in ischemic retinopathy, it is not known at what concentrations it becomes retinotoxic. The purpose of this study was to determine the concentrations of intravitreal APC that are safe and those that are toxic for the retina, using rabbit eyes. METHODS: The left eyes of 12 rabbits received an intravitreal injection of 1.5 to 150 µg of APC in 0.1 ml of saline. The fellow eyes were treated with an intravitreal injection of the same amount of saline. Slit-lamp examination, fundus examination, fluorescein angiography (FA), and electroretinograms (ERGs) were performed before and at different times after the injection. The eyes were enucleated at 6 months after the injection and examined histologically. RESULTS: The clinical and histological differences between the control eyes and the eyes that had APC injections up to 15 µg were not significant. Localized retinal edema was observed in two of three eyes with 150 µg of APC immediately after the injection. In these two eyes, chorioretinal atrophy was observed in the area of the retinal edema at 6 months, which corresponded with a hyperfluorescent area in the FA images and focal retinal degeneration histologically. No significant changes were detected in the full-field ERGs in the eyes treated even with 150 µg of APC throughout the observation period. CONCLUSION: Our results show that an intravitreal injection of APC at a dose ≤15 µg is safe, but 150 µg of APC can be toxic to the retina.

Comparison of spectral-domain versus time-domain optical coherence tomography in management of age-related macular degeneration with ranibizumab.

PURPOSE: To compare the ability to delineate and detect patterns of choroidal neovascularization (CNV) activity in patients with exudative age-related macular degeneration (AMD) after ranibizumab treatment between time-domain optical coherence tomography (TD-OCT) and 4 different spectral-domain optical coherence tomography (SD-OCT) devices. DESIGN: Prospective, consecutive case series. PARTICIPANTS: Sixty-one eyes of 58 patients with exudative AMD after ranibizumab treatment were included in this study. METHODS: All patients were imaged with TD-OCT and at least 1 of 4 different SD-OCT devices at the same visit after ranibizumab treatment. The OCT images were analyzed in a masked fashion by 2 independent graders (KS, TY) to delineate and detect the presence of CNV activity defined as the presence of subretinal fluid, intraretinal cysts, intraretinal fluid, sub-retinal pigment epithelium (sub-RPE) fluid, or a combination thereof. The automated evaluation of retinal thickness also was analyzed between devices. MAIN OUTCOME MEASURES: Evidence of CNV activity on linear B-scans and 3-dimensional so-called cube scans on SD-OCT and linear B-scan on TD-OCT. RESULTS: In linear B-scan mode, all 4 SD-OCT devices were superior in their ability to delineate sub-RPE fluid compared with TD-OCT (P<0.05). Three of 4 SD-OCT devices were superior in delineating intraretinal fluid, and 2 of 4 SD-OCT devices were superior in delineating subretinal fluid and intraretinal cysts (P<0.05). In the 3-dimensional so-called cube mode, all 4 SD-OCT devices were superior in detecting subretinal fluid and 2 of 4 SD-OCT devices were superior in detecting sub-RPE and intraretinal fluid (P<0.05). There were significant correlations in center point thickness between all SD-OCT devices and TD-OCT (P<0.01), and 3 of 4 and 1 of 3 SD-OCT devices showed significant differences from TD-OCT in center point thickness (P<0.01) and center subfield thickness (P<0.001), respectively. CONCLUSIONS: SD-OCT is superior to TD-OCT in evaluating for CNV activity in patients with wet AMD after ranibizumab injection. Retinal thickness measurements between SD-OCT and TD-OCT also were significantly different. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Comparison of surgical treatments for central retinal vein occlusion; RON vs. cannulation of tissue plasminogen activator into the retinal vein.

PURPOSE: To compare the surgical outcomes and evaluate the effectiveness of two treatments for central retinal vein occlusion: radial optic neurotomy (RON) and cannulation of tissue plasminogen activator (tPA) into the retinal vein (tPA). METHODS: This study consisted of 22 eyes. The inclusion criterion was a best-corrected visual acuity of < or =20/60 due to central retinal vein occlusion. The exclusion criteria were previous treatment and the presence of ocular neovascularization. Patients were randomized into RON or tPA groups (n = 11 each). Best-corrected visual acuity, macular thickness, and complications were recorded. RESULTS: The mean best-corrected visual acuity changed from 16/200 at baseline to 20/167 at 12 months in RON (P = 0.217) and from 10/200 to 20/200 in tPA (P = 0.051). The preoperative macular thicknesses decreased from 1,059 microm to 406 microm 12 months postoperatively in RON (P < 0.001) and from 1,121 microm to 271 microm (P < 0.001) in tPA. Neovascular glaucoma developed in 2 eyes (18%) in RON and in 4 eyes (40%) in tPA. Visual field defects associated with surgery were seen in 2 eyes (18%) in RON. CONCLUSION: There was no significant difference in surgical outcomes between the two procedures. Although best-corrected visual acuity and macular edema improved, the incidence of neovascular glaucoma was high. It is, therefore, still uncertain whether these treatments are effective.

Activated protein C rescues the retina from ischemia-induced cell death.

PURPOSE: Ischemia causes severe and persistent visual loss in many eye diseases, including central retinal vein occlusion (CRVO) and diabetic retinopathy. Activated protein C (APC) has been demonstrated to reduce the cell death associated with ischemia in the brain and kidney. This study was performed to examine the ability of APC to rescue hypoxia-induced retinal cell death in vitro and in vivo. METHODS: Retinal pigment epithelium (RPE) and photoreceptor cells were placed in either a normoxic or a hypoxic chamber. Immediately before they were subjected to ischemia, the cultures were treated with APC (3-240 µg/mL). Incubation was followed by an MTT assay to determine the number of viable cells. The activity of caspase-3, -8, and -9 in RPE cells was also analyzed. Various concentrations of APC were intravitreally injected in a rat CRVO model, followed by TUNEL staining to detect the in vivo effects of APC. RESULTS: Lower concentrations of APC (0.3-30 µg/mL) showed a cell-protective effect against hypoxia in vitro, whereas higher concentrations (≥120 µg/mL) demonstrated cytotoxicity in both RPE and photoreceptor cells. Caspase-3, -8, and -9 were activated when the cells were exposed to hypoxia, but this activation was significantly inhibited by APC. Experimental CRVO-induced retinal cell apoptosis was reduced dramatically by intravitreal injection of APC. CONCLUSIONS: APC can reduce ischemia-induced cytotoxicity both in vitro and in vivo via blocking the activation of caspase-3, -8, and -9. APC may be a promising candidate for protecting the retina from ischemia.

Simultaneous intravitreal injection of triamcinolone acetonide and tissue plasminogen activator for central retinal vein occlusion: a pilot study.

PURPOSE: To evaluate the efficacy and safety of simultaneous intravitreal injection of triamcinolone acetonide (TA) and tissue plasminogen activator (tPA) for macular oedema associated with central retinal vein occlusion (CRVO). METHODS: Twenty eyes of 20 patients with CRVO were enrolled. A mixture of TA (4 mg) and tPA (25 µg) was injected into the vitreous of 20 eyes with CRVO. Best corrected visual acuity (BCVA) and macular thickness before and 1, 3, 6 and 12 months after the procedure were measured. RESULTS: The BCVA improved three lines or more in 65%, 55%, 55% and 53% of eyes and the mean macular thickness decreased from 1072 µm to 455, 450, 480 and 409 µm (p<0.001) at 1, 3, 6 and 12 months, respectively. Fifteen (75%) of the 20 eyes required at least one additional injection to prevent a recurrence of macular oedema. The intraocular pressure increased in four eyes. CONCLUSION: Overall, intravitreal injection of the TA/tPA mixture improved the BCVA by three lines or more in at least 50% of eyes and decreased the mean macular thickness at four time points without serious side effects. A randomised clinical trial is necessary to evaluate the efficacy of this treatment.

Increased retinal toxicity of intravitreal tissue plasminogen activator in a central retinal vein occlusion model.

BACKGROUND: Intravitreal injection of tissue plasminogen activator (tPA) is used to treat several ocular conditions, although excessive doses of intravitreal tPA cause retinal toxicity. Toxicity may increase in the ischemic retina, such as in central retinal vein occlusion (CRVO), because tPA toxicity to neural tissues increases under ischemic conditions. We investigated tPA toxicity to the retina in a CRVO rat model. METHODS: CRVO was induced in pigmented rats with rose Bengal-assisted laser photothrombosis. One hour after CRVO induction, 3 microl of tPA (0.075, 0.75, 3, or 7.5 microg) was injected intravitreally. Eyes that did not receive laser treatment, which served as non-CRVO controls, received tPA (0.75, 3, or 7.5 microg). The same amount of balanced salt solution (BSS) was injected as a nondrug control. Eyes were enucleated at 12 hours after injection, and terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) staining was performed to evaluate retinal cell apoptosis. RESULTS: The number of TUNEL-positive cells increased in a dose-dependent manner in both non-CRVO and CRVO group and significantly (P = 0.002) increased when 0.75, 3, or 7.5 microg of tPA was injected into the CRVO eyes. When comparing the number of TUNEL-positive cells between the eyes with and without CRVO that received the same treatment, apoptosis significantly increased in CRVO eyes. CONCLUSIONS: Retinal toxicity associated with intravitreally injected tPA can increase in a dose-dependent manner and be exacerbated in CRVO eyes, suggesting that the dose of tPA should be reduced when tPA is used to treat eyes with CRVO.