Ocular Response to Millimeter Wave Exposure Under Different Levels of Humidity

Abstract

It is known that millimeter waves (MMW) are absorbed by surface tissue such as skin and the cornea. We previously demonstrated that MMW damages the eye by heat accumulation and transfer. To examine the influence of humidity on such damage, we investigated the difference in MMW-induced ocular tissue temperature increase under high (70%) and low (30%) relative humidity. Eyes of pigmented rabbits (Dutch, 11-15week old) were exposed unilaterally to 40-GHz 200 mW/cm 2 MMW for 5 or 30 min at the center of the pupillary area with a spot-focus type lens antenna. Infrared thermography was used to measure corneal surface temperature during exposure. Temperature of corneal stroma and lens nucleus were measured using a fluoroptic thermometer during 0-30-min exposure. To visualize the dynamic change of temperature and its distribution in the anterior chamber, saline containing 0.2% microencapsulated thermochromic liquid crystal (MTLC) was injected into the eye anterior chamber. All three temperature measurements were much higher under high than low humidity at 24°C room temperature and MTLC results showed the same trend during MMW exposure. These findings indicate that humidity affects MMW-induced ocular temperature elevation. We showed that low humidity during MMW exposure decreased heat accumulation and transfer, whereas high humidity increased the thermal effect. The present data demonstrated that controlling the environmental humidity might have an impact on ocular damage in eyes exposed to MMW.

Clinical Course of High-Frequency Millimeter-Wave (162 GHz) Induced Ocular Injuries and Investigation of Damage Thresholds

“…It was reported several decades ago that energy in the frequency range 10-300 GHz was absorbed by the skin surface and the surface tissue of eyeballs [1]. Studies have examined the effects to eyes of MMW exposure [2][3][4][5][6][7][8], but because their exposure methodology (especially, shape of antenna (radiation pattern of antenna) for MMW delivery) and experimental animals differed, the results of these studies cannot be directly compared. We have previously reported data on the threshold of eye injury in Dutch rabbits exposed to 40, 75, and 95 GHz MMW using uniform experimental procedures [7].…”

Design and Implementation of a Specialised Millimetre-Wave Exposure System for Investigating the Radiation Effects of 5G and Future Technologies

“…All the mentioned studies have addressed the ocular damage induced by RF radiation. However, as Kojima [ 26 ] pointed out, direct comparisons of the study results are not feasible due to variations in their exposure methods, such as the antenna’s shape (i.e., radiation pattern) for mmWave delivery and the use of different experimental animals. Consequently, more research is necessary, and exposure systems must be developed to replicate various studies involving different biological tissues to ensure the accuracy of the results.…”

“…This comprehensive guide, outlining both advantages and limitations, serves as a valuable resource for scientists seeking to replicate exposure systems operating at higher frequencies. We aimed to facilitate further bioelectromagnetics research by conducting experiments, enabling direct comparisons with international studies in the field [ 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. Additionally, our aim was to introduce a novel feature: a small radiation spot size specifically designed to study localised exposure.…”