MILLIMETER WAVE ABSORPTION IN THE NONHUMAN PRIMATE EYE AT 35 GHz AND 94 GHz

Abstract

The purpose of this study was to evaluate anterior segment bioeffects of pulsed 35 GHz and 94 GHz microwave exposure in the nonhuman primate eye. Five juvenile rhesus monkeys (Macaca mulatta) underwent baseline anterior segment ocular assessment consisting of slit lamp examination, corneal topography, specular microscopy, and pachymetry. These studies were repeated after exposure of one eye to pulsed 35 GHz or 94 GHz microwaves at varied fluences, with the other eye serving as a control. The mean fluence required to produce a threshold corneal lesion (faint epithelial edema and fluorescein staining) was 7.5 J cm(-2) at 35 GHz and 5 J cm(-2) at 94 GHz. Transient changes in corneal topography and pachymetry were noted at these fluences. Endothelial cell counts remained unchanged. Threshold corneal injury from 35 GHz and 94 GHz microwave exposure is produced at fluences below those previously reported for CO2 laser radiation. These data may help elucidate the mechanism of thermal injury to the cornea, and resolve discrepancies between IEEE C95.1 (1999), NCRP (1986), and ICNIRP (1998) safety standards for exposure to non-ionizing radiation at millimeter wavelengths.

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

“…Under pulse wave conditions, the thresholds for corneal injury, corneal edema, and corneal epithelial defect were found to be 7.5 J/cm 2 for 35 GHz and 5.0 J/cm 2 for 94 GHz [5], suggesting that different frequencies have different ocular effects. These earlier studies employed a circular horn antenna [4,6] or an open-ended waveguide [5]. Because their exposure methodology and experimental animals differed, the results of these studies cannot be directly compared.…”

“…Several in vivo studies in experimental animals have evaluated the specific effects of MMW [4][5][6]. Frequency-specific thresholds for ocular damage were observed at 35 and 107 GHz.…”

“…Exposure to 35 GHz MMW was associated with corneal damage, including high levels of corneal epithelial injury, persisting for almost 2 days, whereas exposure to 107 GHz was associated with transient injury to the corneal stroma, albeit more powerful in inducing immediate corneal stromal damage [4]. Under pulse wave conditions, the thresholds for corneal injury, corneal edema, and corneal epithelial defect were found to be 7.5 J/cm 2 for 35 GHz and 5.0 J/cm 2 for 94 GHz [5], suggesting that different frequencies have different ocular effects. These earlier studies employed a circular horn antenna [4,6] or an open-ended waveguide [5].…”

Characteristics of ocular temperature elevations after exposure to quasi- and millimeter waves (18-40 GHz)

“…Although both induced similar corneal damage immediately after exposure, the effects of exposure to 35 GHz continued longer than those of exposure to 107 GHz, a difference that may be due to wavelength specificity or relative biological effectiveness. In contrast, a comparison of the threshold of tissue damage between 35 and 94 GHz found that the higher frequency had a lower tissue damage threshold [4]. Depth of penetration of electromagnetic fields into an irradiated object decreases as the frequency of the incident field elevations [7].…”

“…Although many studies have assessed the effects of microwave exposure on the eye, few studies have evaluated the specific effects of MMWs [2][3][4][5][6]. Frequency specific thresholds (MMW pulse wave) for ocular damage between 35 and 94 GHz were observed in rhesus monkey eyes, with the mean influence to develop corneal damage being 7.5 J/cm 2 at 35 GHz and 5 J/cm 2 at 94 GHz [4]. In rabbit eyes, 107 GHz effectively produced immediate stromal damage, which was generally gone by the next day, whereas the effects of 35 GHz were persistent and were almost always present the next day [2].…”