1/11/2024 0 Comments Caprine eyesAfter sub-methyl-blue solution was injected into the retinal vessel, the distal branch vein stained blue and the main vein remained light red. Occlusion of a retinal main vein was established by vascular endodiathermy at a site just in the vessel’s first branching. Then, the retinal vessel appeared red after injection of acid red G. Complete displacement of blood by Krebs solution made the retinal vessel appear transparent. To further demonstrate the feasibility of retinal vein bypass surgery in this study, we performed micro-vascular maneuvers in a closed, arterially perfused caprine eyeball using temporary keratoprosthesis (TKP) vitrectomy approach. 10 However, it did not represent the feasibility of retinal bypass surgery in the living eye as open-sky approach used in the above study was far from the real condition. 7, 8, 9 Bypassing the occluded retinal vessel segment with artificial graft, similar to clinical cure for myocardial ischemia using coronary artery bypass grafting, has been demonstrated feasible in an animal eyecup model. Recent research of this subject has mostly focused on the re-establishment of retinal venous outflow, including intravascular injection of vasoactive substances, 2 arteriovenous crossing sheathotomy, 3, 4, 5, 6 and chorioretinal anastomosis. This early work indicated that the more advanced retinal vascular bypass surgery in in vivo eye may be feasible in the future.Īs a very common retinal vascular disorder, probably second only to diabetic retinopathy, 1 branch retinal vein occlusion (BRVO) is short of effective therapies at present. This study demonstrated that bypassing the occluded segment of retinal main vein can be successfully performed in a closed-sky eyeball model of isolated, arterially perfused caprine eye. Good results were obtained in 23 of 38 (60%) caprine eyes. Bypassing of the occluded retinal main vein segment was accomplished with the combination of these maneuvers. Puncturing, catheterization, and endodiathermy were viable by closed-sky approach using keratoprosthesis. Bypass of the occluded retinal vein segment was thus achieved, and the patency of this vascular bypass was confirmed by intravascular staining. A sealed connection between the vessel and the tube was obtained by endodiathermy. Catheterization was achieved using a flexible polyimide tube, with each end inserted into the vessel wall opening. Two openings, several millimeters apart, were created by vascular punctures in both the main vein and its branch vein wall straddling the induced occluded segment. The main retinal vein was blocked by endodiathermy at the site of the vessel’s first branching. All retinal micro-vascular maneuvers were performed in a closed-sky eyeball. For each eye, the retinal vessel was perfused by Krebs solution via ophthalmic artery, and pars plana vitrectomy was performed using temporary keratoprosthesis. Isolated caprine eyes were used in this study. Humans and predatory animals that don’t mainly rely on ambush hunting have round pupils that are suited for chase hunting during daylight hours.Ĭircular pupils are also found in birds, wolves, and some big cats like lions that have different hunting styles than other felines.To investigate the feasibility of bypassing occluded segments of retinal venous main vessels in isolated, arterially perfused caprine eyes via the closed-sky vitrectomy approach using keratoprosthesis. Some animals, and us humans, have pupils that are round all the time. This type of pupil shape helps predators determine the distance between themselves and their prey.Īs we see with domestic cats, their pupils can become round and large in the dark to help them see better to hunt in low light. Predators, especially ambush predators like cats and snakes, have vertical slit pupils. Horses have them, and so do sheep, deer, and antelope. Other grass-eating prey animals have similar eyes, you just may not see them as well because their irises are darker. ![]() We often notice a goat’s strange pupils, but they are not unique. Goats and other grazing prey animals have horizontal pupils that help them scan for stalking predators all around them while they have their heads down eating grass. Most are related to an animal’s place in the food chain. Scientists have identified several pupil shapes. Why Do Some Animals Have Horizontal Pupils?
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