| Purpose. To investigate the safety, feasibility and efficacy of injection of tissue plasminogen activator into optic disc for the treatment of retinal vein occlusion in rabbits, and to evaluate the efficacy of Edaravone, a new synthesized free radical scavenger on an experimental model of retina vein occlusion in rat.Methods. Electrodes for recording VEPs were implanted into the skull of rabbits. In part one, to investigate the safety and feasibility of injection of tPA into the optic disc. Each eye in group one (6 eyes) received injection of tPA 25 ug in 0.1 ml BSS. Each eye in group two (6 eyes) received injection of tPA 12.5 μg in 0.1 ml BSS. Each eye in group three (6 eyes) received injection of 0.1 ml BSS. Eyes (6 eyes) in group four as a normal control received no injection. One day, 3 days, 1 week, 2 weeks and 4 weeks after injection, the eyes were examined by slit lamp biomicroscopy, indirect ophthalmoscopy, visual evoked potentials and electroretinography, and then harvested for histopathological examination. In part two, Rose Bengal-mediated argon laser retinal vein photothrombosis was produced. Vein occlusion was confirmed by fluorescein angiography. Rabbits in treatment group (12 eyes, 24 veins) were treated with optic disc injection of tPA (12.5 ug in 0.05 ml BSS). Control animals (12 eyes, 24 veins) received optic disc injection of 0.05 ml BSS. Fluorescein angiography was repeated to determine the recanalization of the vessel at third and seventh day after treatment. At the same time, slit lamp biomicroscopy, indirect ophthalmoscopy and fundus photography were performed. Eyes wereharvested at 7 days after treatment for histopathological examination. Rose Bengal-mediated argon laser retinal vein photothrombosis was produced. Vein occlusion was confirmed by fluorescein angiography. Rats in treatment group (18 eyes) were treated with subconjunctival injection of Edaravone300μg/0.2ml. Control animals (18 eyes) received subconjunctival injection of 0.2ml BSS. Slit lamp biomicroscopy, indirect ophthalmoscopy and fundus photography were performed. Eyes were harvested at3 and 7 days after treatment for histopathological examination and the evaluation the levels of the formation of malondialdehyde, one marker for lipid peroxidation and the levels of Interleukin-6, one of the inflammatory cytokines.Results. No obvious evidence of optic nerve or retinal toxicity or damage from ophthalmoscopy, VEPs, ERGs, and histology was seen with the injection of tPA into optic nerve. The means of the cell counts in the optic nerve section of equal size of 1 mm~2 were 2481.3 ± 268.2, 2363. 5 ± 301.9, 2455.5 ± 272.1, and 2417.8 ± 302.9, respectively in group 1, 2, 3 and 4 (P = 0.0741). The means of the latency of the first peak of the VEPs were 24.60 ± 1.54, 24.09±1.92, 24.01 ± 1.96 and 24.57 ± 1.25 respectively ( P = 0.4112). The means of the amplitude of the first peak of the VEPs were 123.91 ± 41.77, 145.16 ± 41.22, 132.36 ± 48.22 and 116.78 ± 29.44 respectively (P = 0.0649). The means of the latency of A-waves were 5.95 ± 0.42, 5.86 ± 0.41, 5.87 ± 0.46 and 5.81±0.33 respectively (P = 0.6279). The means of the amplitude of A-waves were 110.28 ± 13.91, 111.97± 15.28, 109.73 ± 15.90 and 107.74±10.87 respectively (P = 0.7248). The means of the amplitude of B-waves were 150.80±11.86, 147.59±13.60, 144.52±16.54 and 141.00±20.46 respectively (P = 0.0957). The incidence of the patency of the vessels in treatment animals was 70.0% (14/20), while in the control animals was 16.7% (4/24)(P = 0.001). Focal vein occlusion was successfully produced by Rose Bengal-mediatedargon laser retinal vein photothrombosis. The numbers of laser application needed to produce complete RVO were not significantly different in the treatment and control animals (Control group: 22.3; Treatment group: 21.2; P — 0.4044). Immediately after occlusion, there was a marked dilation and tortuosity of the vein peripheral to the site of occlusion and narrowing of arteries. Retinal hemorrhages, retinal edema and exudative retinal detachment... |
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