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M.W. ten Hove, C. Lutchman; Modelling of Induced Retinal Hypothermia . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5315.
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Purpose: The current therapy for central retinal artery occlusion is difficult and often ineffective. Previous studies have shown that inducing hypothermia to a level of 29oC can preserve ischemic retinal tissue. The purpose of this experiment is to determine whether hypothermia is achievable in the retina when ice water is applied to the anterior 1/3 of the globe. This may prove to be an effective and practical adjunctive treatment for CRAO. Methods: With a donor human globe, an incision was made adjacent to the optic nerve insertion, revealing choroid and retina. The globe was placed into a Styrofoam container such that the anterior 1/3 was protruding from the container with the cornea faced down, to model the supporting ligaments of the globe in the orbit. This container was then lowered into a water bath initially at a temperature of 38oC. The Styrofoam container was also filled with water at a temperature of 38oC. A thermocouple was used to monitor the temperature of the water bath. The temperature of the posterior 2/3 of the globe and surrounding water was filmed using an infrared camera (a ThermaCAM S60). Once the temperature of the globe was equilibrated to 38oC, the anterior 1/3 of the globe was placed in a different bath of ice water. The cooling effect of the choroid–retina complex over time was recorded at 30–second intervals until a new equilibrium was achieved. Results: The posterior water bath was maintained between 38oC and 40oC while the anterior water bath was maintained between 5oC and 7oC. As expected, there was an exponential decrease in temperature of the choroid–retina complex adjacent to the optic nerve insertion, which dropped to a temperature of 29.6oC by 30 minutes. Conclusions: This preliminary study confirms that it is possible to cool the retina to below 30oC by applying ice water to the anterior 1/3 of the globe while the posterior 2/3 of the globe remains at body temperature. We are currently refining our model by implementing tighter temperature controls as well as by attempting to obtain a temperature gradient across the globe.
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