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S Maguluri, B Khoobehi, ME Hartnett, LG Carnahan, RL Grinstead, HA Elzembely; Iris Neovascularization Model and an Innovative Imaging Technique for Visualization of Individual Iris Vessels . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4356.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To create a reliable, reproducible uvea neovascularization model in rats using an optical set up that allows imaging of individual normal and neovascular microvessels. Methods: Iris neovascularization was created by inducing retinal ischemia and lowering intraocular pressure (IOP) in one eye each of 12 rats. Retinal ischemia was induced by closing central retinal veins using an IR laser at 810 nm (laser parameters: power 300mW, exposure time 500 ms, and spot size 500 µm). To keep IOP low, a 6-0 suture was passed through the center of the cornea after the retinal vessels were closed to allow a slow release of aqueous humor. Individual iris vessels were visualized by using an optical set up consisting of a 60-diopter lens placed in front of a scanning laser ophthalmoscope (SLO), in combination with injection of a high dose (0.3 ml at a concentration of 2.25 mg/kg) of an infrared dye such as indocyanine green (ICG). The SLO and the 60 diopter lens were positioned in a conjugate focal plane. The iris angiogram was performed with this new optical set up before, immediately after, and 8, 16, 20, 23, 26, and 30 days after the laser procedure. Sodium fluorescein angiograms of the iris were performed for comparison with the ICG images on the same schedule. The normal, non-ischemic eye of each rat served as a control. Results: Seven of the 12 (58%) of the irises became neovascular; neovascularization in these eyes peaked 23 days after the laser procedure. The injection of ICG allowed visualization of each individual microvessel. Immediately after injection, the vessels were not leaky and consequently, the structure of the iris vessels was easily seen. Ten minutes after the ICG injection, the vessels became leaky and fluoresced diffusely. The observed neovascularization seemed to begin closer to the inner ring. Iris angiograms using sodium fluorescein performed in the same animals confirmed our ICG findings; however, ICG was able to distinguish the pattern of normal and leaky vessels which is not possible with sodium fluorscein. Conclusion: This innovative technology can be used to image iris neovascularization for diagnostic and treatment purposes, such as after treatment with anti-angiogenesis agents.
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