Ocular Effects of Exposure to 40, 75, and 95 GHz Millimeter Waves

Abstract

The objective of this study was to develop a model of ocular damage induced by 40, 75, and 95 GHz continuous millimeter waves (MMW), thereby allowing assessment of the clinical course of ocular damage resulting from exposure to thermal damage-inducing MMW. This study also examined the dependence of ocular damage on incident power density. Pigmented rabbit eyes were exposed to 40, 75, and 95 GHz MMW from a spot-focus-type lens antenna. Slight ocular damage was observed 10 min after MMW exposure, including reduced cornea thickness and reduced transparency. Diffuse fluorescein staining around the pupillary area indicated corneal epithelial injury. Slit-lamp examination 1 day after MMW exposure revealed a round area of opacity, accompanied by fluorescence staining, in the central pupillary zone. Corneal edema, indicative of corneal stromal damage, peaked 1 day after MMW exposure, with thickness gradually subsiding to normal. Three days after exposure, ocular conditions had almost normalized, though corneal thickness was slightly greater than that before exposure. The 50% probability of ocular damage (DD 50 ) was in the order 40 > 95 ≈ 75 GHz at the same incident power densities. J Infrared Milli Terahz Waves (2018) 39:912-925 https://doi

Ocular Response to Millimeter Wave Exposure Under Different Levels of Humidity

“…A standardized exposure system for in vivo rabbit eye was established at 40, 75, and 95 GHz [12]. Note that the frequency (40 GHz) was selected considering penetration depth into the eye.…”

“…Briefly, the power source for 40-GHz continuous MMW comprised an 83650B signal generator (Agilent Technologies, Inc., Santa Clara, CA, USA) and a 40-W TWT amplifier (Ka Band, ETM Electromatic Inc., Newark, CA, USA). The MMW were transmitted through a conical horn antenna which had a 15-cm diameter lens to spot-focus the power localizing it to the eye [12]. Power sensors monitored incident power to the antenna and reflected power from the antenna via a directional coupler to ensure the desired incident power density (Fig.…”

“…Before exposure, eyes were examined by slit lamp microscopy (SL-130, Zeiss, Tokyo, Japan) to rule out presence of preexisting irregularities in the corneal surface and anterior segment. The pre-exposure examination included slit lamp images of the cornea, lens, and iris and fluorescent staining of corneal epithelium as described previously [10,12,16]. We exposed millimeter wave to one eye (right eye) and the other eye (left eye) was used as a non-exposed control.…”

“…We previously reported that aqueous humor convection is an important factor in heat transfer from the cornea to the lens or vitreous humor [16]. Moreover, our previous study suggested that not only heat transfer within the cornea but heat exchange between the cornea surface and ambient air plays an important role in corneal damage from MMW exposure [12]. Therefore, the effect of ambient humidity, which may affect the rate of tear film evaporation, warrants investigation.…”

“…Safety issues regarding tissue surface heating from MMW exposure have also been reviewed [8]. In addition, other recent studies have also reported acute effects from MMW exposure to the eye [9][10][11][12]. Nowadays, the number of people working under MMW exposure has been increasing, yet there is a paucity of data on the potential biological effects of such exposure.…”