Paper ACUTE OCULAR INJURIES CAUSED BY 60-GHZ MILLIMETER-WAVE EXPOSURE Masami Kojima,* †‡ Masahiro Hanazawa, § Yoko Yamashiro,* Hiroshi Sasaki,* † Soichi Watanabe, § Masao Taki,** Yukihisa Suzuki,** Akimasa Hirata, †† Yoshitsugu Kamimura, ‡‡ and Kazuyuki Sasaki* §§ Abstract—The goal of this study was to examine the clinical course of 60-GHz millimeter-wave induced damages to the rabbit eye and to report experimental conditions that allow reproducible induction of these injuries. The eyes of pigmented rabbits (total number was 40) were irradiated with 60-GHz millimeter-waves using either a horn antenna or one of two lens antennas (6 and 9 mm diameter; 6, 9) Morphological changes were assessed by slit-lamp microscopy. Additional assessments included corneal fluorescein staining, iris fluores- cein angiography, and lens epithelium light microscopy. Under the standardized eye-antenna positioning, the three antennas caused varying damages to the eyelids or eyeglobes. The most reproducible injuries without concurrent eyelid edema and corneal desiccation were achieved using the 6 lens antenna: irradiation for 6 min led to an elevation of the corneal surface temperature (reaching 54.2  0.9°C) plus corneal edema and epithelial cell loss. Furthermore, mitotic cells appeared in the pupillary area of the lens epithelium. Anterior uveitis also occurred resulting in acute miosis (from 6.6  1.4 to 2.2  1.4 mm), an increase in flares (from 6.7  0.9 to 334.3  130.8 photons per second), and iris vasodilation or vessel leakage. These findings indicate that the three types of millimeter-wave antennas can cause thermal injuries of varying types and levels. The thermal effects induced by millimeter-waves can apparently penetrate below the surface of the eye. Health Phys. 97(3):212–218; 2009 Key words: exposure, occupational; laboratory animals; mi- crowaves; radiation, nonionizing INTRODUCTION WITH RECENT advances in electromagnetic field (EMF) technology, EMFs with super and extremely high frequen- cies, including millimeter-waves (MMWs), are likely come into wide-spread use in daily life, with applications ranging from wireless transmission of voice and data to intelligent transport systems such as automobile collision radar. The rapid development of these new technologies is likely to increase public concerns about possible health effects of exposures to very high frequency EMFs, including MMWs. Safety guidelines on EMF exposures published by various organizations, including the International Com- mission on Non Ionizing Radiation Protection (ICNIRP 1998) and the International Committee on Electromag- netic Safety (ICES) of the Institute of Electrical and Electronics Engineers (IEEE 2005), cover the frequency range of MMWs, or up to 300 GHz. These guidelines are based on established scientific evidence and are mainly concerned with thermal effects. Few studies, however, address the rationale for the exposure limits at MMW frequencies. The limit values for MMW exposures were derived primarily from extrapolations of experimental data for frequencies up to several GHz, or from the effects of infrared radiation. To confirm the scientific basis for the exposure limits in the MMW region, it is necessary to obtain data derived directly from experi- ments using MMWs. Of the human tissues, the eye is considered most vulnerable to MMW-induced injuries as it is located on the surface of body where most energy of MMWs is dissipated. While previous studies have investigated the ocular effects of EMF exposures, there is little specific information on the effects of MMWs. For example, exposure to MMWs can have varying effects on the cornea (Rosenthal et al. 1976; Kues et al. 1999; Chalfin et al. 2002). However, since damage to the corneal epithe- lium can also be caused by simple desiccation (due to mechanical prevention of blinking; Fujihara et al. 1995), * Division of Vision Research for Environmental Health, Medical Research Institute, Kanazawa Medical University, 1-1, Daigaku, Uchinada-machi, Ishikawa, 920-0293, Japan; † Department of Oph- thalmology, Kanazawa Medical University, 1-1, Daigaku, Uchinada- machi, Ishikawa, 920-0293, Japan; ‡ School of Nursing, Kanazawa Medical University, 1-1, Daigaku, Uchinada-machi, Ishikawa, 920- 0293, Japan; § National Institute of Information and Communica- tions Technology; ** Department of Electrical Engineering, Tokyo Metropolitan University; †† Department of Computer Science and Engineering, Nagoya Institute of Technology; ‡‡ Department of Infor- mation Science, Faculty of Engineering, Utsunomiya University; §§ Visual Science Course, Department of Rehabilitation, Faculty of Medical Science and Welfare, Tohoku Bunka Gakuen University. For correspondence contact: Masami Kojima, Department of Oph- thalmology, Kanazawa Medical University, 1-1, Daigaku, Uchinada, Kahoku-gun, Ishikawa, 920-0293, Japan, or email at m-kojima@ kanazawa-med.ac.jp. (Manuscript accepted 24 April 2009) 0017-9078/09/0 Copyright © 2009 Health Physics Society 212