Mechanism Of Oxidative Damage In The Rat Lens After In Vivo Exposure To Infrared Radiation

Clinical significanceAs infrared ray becomes more in-depth and wide range of applications in the military, satellite, industry, health and scientific research, the infrared pollution problem has been gradually arises. Infrared radiation is invisible light and an integral part of the electromagnetic radiation. All the substance above absolute zero (-273.15℃) can produce infrared. A commonly used sub-division scheme is Near-infrared (NIR), Mid-infrared (MIR), and Far infrared (FIR). NIR is sometimes called a short-wave infrared. It is electromagnetic waves between the visible and mid-infrared. According to the definition of ASTM (American Society for Testing and Materials Testing Association), near-infrared is the electromagnetic waves and the wavelength range is 780～2526 nm. Temperature is higher, the wavelength is shorter, and the near infrared radiation is increasing. The strong infrared radiation can cause skin and eye damaged. If our eye exposure infrared radiation long time, it can cause cataract.In this project we aimed to investigate the evolution of cataract development in the rat lens and the temperature evolution in the eye after in vivo exposure to IR. Moreover, we aimed to elucidate the photochemical mechanisms in the lens from near infrared radiation.Experiment 1:Experimental evidence for photochemical mechanisms in infrared radiation induced cataractPurpose:To elucidate the photochemical mechanisms in the lens from infrared radiation.Methods:Altogether 16 six-weeks-old albino Sprague-Dawley rats were randomly divided into four measurement groups of 4. The rat was anesthetized with Ketamine (95mg/kg) and xylazine (14mg/kg) before exposure. The pupil is dilated on both eyes with tropicamide,5mg/ml, ten minutes before exposure. Then, the rats were exposed unilaterally in vivo to 1090 nm,8s exposure time with a 2 mm spot on the anterior lens surface. Four post-exposure time groups of 6,18,55,168 hours respectively were exposed unilaterally in vivo to 8s of 1090 nm,0.7kJ/cm2 (power6.2 W), quasi-top hat spatial distribution with a 2 mm spot on the anterior lens surface within the dilated pupil. After, the intended post-exposure time, the difference of light scattering between the lenses from the same animal was measured.Results:After 8s of 0.7kJ/cm2 within a 2 mm spot on the lens surface, the light scattering increase in the lens was delayed at least 18 hours after exposure.Conclusion:Infrared radiation induced cataract was at least 18 hours delayed after exposure, The current data proves that Infrared cataract contains a potential photochemical reaction.Experiment 2:Ocular Temperature Elevation and Lens Light Scattering Induced by In Vivo Exposure to 1090 nm Infrared RadiationPurpose:The aim of this study was to determine the temperature evolution in the eye during an in vivo exposure to 1090nm for 8 seconds at just above threshold intensity.Methods:Altogether 20 six-weeks-old albino Sprague-Dawley rats were randomly divided into two measurement groups of 10. The animals were anesthetized and the pupils were bilaterally dilated prior to exposure. All animals were unilaterally exposed to 6.2 W coherent infrared radiation at 1090 nm with a spot size of 3 mm within the dilated pupil for 8 seconds (0.7 kJ/cm2). In one group, temperature was recorded with thermocouples placed externally at the limbus, in the vitreous just behind lens and on the outer sclera next to the optic nerve, respectively on both eyes. In the other group, one thermocouple was placed externally at the limbus and another thermocouple externally next to the optic nerve, in both eyes. Temperature was recorded during the exposure. The rats were sacrificed immediately after exposure and the difference of light scattering between the lenses from the same animal was measured.Results:In the three-thermocouple measurement group, average temperature rise in the exposed eye was 11 degrees at the limbus,16 degrees in the vitreous behind lens and 15 degrees on the sclera next to the optic nerve. In two-thermocouple measurement group, the temperature elevation in the exposed eye was 9 degrees at the limbus and 26 degrees on the sclera next to the optic nerve, respectively. In both groups, no temperature change was measured in the contralateral eye. In two-thermocouple measurement group, the difference of forward light scattering between exposed and non-exposed contralateral eye was 0.01+0.06. Conclusion:Close to threshold intensity for cataract development at 1090 nm with 8 s exposure time induces a heat elevation behind the lens and externally close to the optic nerve. The cataract development with these exposure parameters is most probably of thermal origin.