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M. Kojima, T. Sakai, Y. Yamashiro, Y. Suzuki, Y. Sakamoto, Y. Kawakami, S. Watanabe, M. Taki, K. Sasaki, H. Sasaki; Investigation of Frequency Specificity of Millimeter Wave Exposure Through Ocular Temperature Measurement and Heat Transportation. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2777. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Response to frequency of millimeter wave: Ocular temperature, and thermal convection in the anterior chamber.
0.2% micro-capsulated thermo-chromic liquid crystal was injected into the anterior chamber of pigmented rabbits. Rabbit eyes were exposed unilaterally to a 26.5, 35 or 40 GHz beams by lens antenna for 3 minutes. The maximum power density of each frequency exposed was at the surface of the corneal center. Anterior chamber slit images were recorded during exposure. Ocular temperature changes (cornea, lens) during 800 mW/cm2 exposure were measured with a Fluoroptic thermometer. The penetration depth of each frequency from the corneal surface was calculated using an electric constant of the cornea.
The calculated penetration depths of each frequency were as follows; 0.83 mm (26.5 GHz), 0.66 mm (35 GHz) and 0.59 mm (40 GHz). Mean changes of corneal and lens temperature (max. temp. - pre-exposure temp, N=5) were +1.8°C, +0.7°C (26.5 GHz); +8.7°C, +2.9°C (35GHz) and +15.5°C, +4.3°C (40 GHz) respectively. Cornea and lens temperature increased with frequency. Normal (non-exposed) aqueous humor flow was characterized by a gradual rise on the crystalline lens side and descent on the cornea side. This convection feature was reversed under exposure to 35 or 40 GHz beam (600 mW/cm2) whereas, exposure to 26.5 GHz did not show any clear convection change. The 1500 mW/cm2 exposure condition showed convection that rose on the lens side and descended on the cornea side.
It was clear that ocular temperature and heat generation was affected by millimeter wave frequency.
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