| Purpose: The theory of blood circulation defect is one of the pathogenesis of glaucomatous optic neuropathy. Model of chronic optic disk ischemia has been induced in cat with endothelin-1 (ET-1) in order to investigate the effect of chronic ischemia on optic nerve. Methods:The experimental study of chronic optic disk ischemia induced by injecting ET-1 into the posterior vitreous13 healthy grown cats were randomly divided into 2 groups, 7 in group A (4 females, 3 males) and 6 in group B (3 females, 3 males). The right eyes were defined as experimental eyes and the left as positive contrast eyes. Before operation, all the cats received eye examination, intraocular pressure (IOP) measurement, analysis of optic disk configuration (C/D area ratio, mean cup depth, maximum cup depth, mean RNFL thickness) using heidelberg retina tomography (HRT),analysis of the microcirculation in optic disk lamina cribrosa (blood flow volume (Vol), blood flow velocity (Flw), erythrocyte flow velocity (Vel)) using heidelberg retina flowmeter (HRF). All the experimental eyes were injected 10μl ET-1 (group A 10-6 M,group B 10-5 M) into the posterior vitreous with 30-G minim syringe general anesthetically twice a week for 4 weeks and the contrast eyes received 10μl corresponding excipient. Before and after every injection all the cats received eye examination, IOP measurement.2 months after the injection finished all the cats received the same examination as preoperationally, then the eyes were enucleated. The optic nerve specimens were cut immediately in the condition of low temperature and made into slices to count optic nerve axon. The experimental study of controlled-delivering ET-1 by surgically implanted osmotic minipumps7 healthy grown cats were included, 4 females, 3 males. The right eyes were defined as experimental eyes and the left as positive contrast eyes.Before operation, all the cats received eye examination, IOP measurement, analysis of optic disk configuration using HRT,analysis of the microcirculation in optic disk lamina cribrosa and analysis of the retinal blood flow parameters using HRF. The osmotic minipump was surgically implanted under the skin around the lateral canthus general anesthetically, the linked catheter (about 20mm long) was placed around the root of retrobulbar optic nerve. The experimental eyes used 2.2×10-5 M ET-1 and the contrast eyes used corresponding excipient. 2 months later all the cats received the same examination as preoperationally, then the eyes were enucleated. The optic nerve specimens were cut immediately in the condition of low temperature and made into slices to count optic nerve axon.Results:The experimental study of chronic optic disk ischemia induced by injecting ET-1 into the posterior vitreousGroup A (10-6 M ET-1)The difference of IOP, optic disk configuration parameters, microcirculation parameters of lamina cribrosa , axon counts between the experimental and contrast eyes pre- and post- operationally is statistically insignificant. Group B (10-5 M ET-1)Compared with the baseline, some of the IOP pre- and postinjection of the experimental eyes are statistically lower (p<0.05),but the difference between IOP of the contrast eyes is statistically insignificant. The difference of optic disk configuration parameters between the experimental and contrast eyes is statistically insignificant. The microcirculation parameters of lamina cribrosa postoperationally in experimental eyes are reduced compared with the baseline (p<0.05), Vol reduced by 33.80%,Flw reduced by 57.73%,Vel reduced by 57.70%,and the difference in contrast eyes is statistically insignificant. The axons of the experimental eyes postoperationally are reduced by 10.70% compared with the baseline (p<0.05). The experimental study of controlled-delivering ET-1 by surgically implanted osmotic minipumpsThere is statistical significance in comparison between baseline and postoperation IOP of experimental eyes (p<0.05). However, it's not such case when turned to contrast...
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