Analysis on Optical and Heat Blocking Characteristics of Near-Infrared Absorbing Lenses

Purpose : To analyze the optical and heat blocking characteristics of NIR absorbing lenses. Methods : To analyze definition, image test charts were photographed with a camera and the images were analyzed by image quality analyzing software. Visual acuity were measured on 32 subjects. To analyze heat blocking characteristics, the pig skin and eyelid were irradiated by NIR and their temperatures were measured by a digital thermometer and a thermal imaging camera. The lens surface temperature was measured after irradiating NIR on the lens, and the heat damage on the lens was analyzed. The subjective satisfaction with definition, glare, heat sensitivity and light perception was evaluated in condition wearing NIR absorbing lenses and tinted lenses. Results : There was no significant difference in definition and visual acuity between NIR absorbing lenses and tinted lenses. The temperature changes of pig skin and human eyelids when wearing NIR absorbing lenses were lower than when wearing tinted lenses. The NIR absorbing lenses irradiated by NIR showed higher surface temperature and was damaged more quickly than the tinted lenses irradiated by NIR. In the survey, the subjective satisfaction of the sharpness (p=0.040) and glare (p=0.000) caused by the NIR absorbing lenses were both higher than that of the blue lens, but there were no significant differences between the gray, brown and green tinted lenses. The subjective satisfaction of the heat sensation (p=0.040) and light quantity (p=0.000) by NIR absorbing lenses were higher than that of the tinted lenses. Conclusion : The sharpness and visual acuity of the NIR absorbing lenses and the tinted lenses were not significantly different, and the NIR absorbing lenses showed better heat blocking effect than the tinted lenses. It is considered that this study suggested the fundamental data on the heat blocking effect of the NIR absorbing lenses.