Investigation of the Ocular Response and Corneal Damage Threshold of Exposure to 28 GHz Quasi-millimeter Wave Exposure.

Electromagnetic radiation energy at millimeter wave frequencies, typically 30 GHz to 300 GHz, is ubiquitously used in society in devices for telecommunications; radar and imaging systems for vehicle collision avoidance, security screening, and medical equipment; scientific research tools for spectroscopy; industrial applications for non-destructive testing and precise measurement; and military and defense applications. Understanding the biological effects of this technology is essential. We have been investigating ocular responses and damage thresholds comparing various frequencies using rabbit eyes and dedicated experimental apparatus. In this study we investigated the 28 GHz quasi-millimeter wave band (wavelength: 10.7 mm), a candidate for 5G communication. Similar to millimeter wave frequencies, ocular damage from exposure to 28 GHz for 6 min (400 mW cm-2) included corneal epithelial damage, corneal edema, and opacity. The incident power density threshold, indicating a 50% probability of ocular damage from exposure for 6 min, was found to be 359 mW cm-2 for 28 GHz. Comparing the ocular exposure area for various millimeter wave frequencies (40, 75, 95 GHz) and 28 GHz quasi-millimeter waves using a thermosensitive liquid crystal capsule, we found that for millimeter waves, even at identical incident power densities, the ocular exposure area decreases as the frequency increases (lens effect). However, this lens effect was not observed at 28 GHz, where the entire anterior segment area was exposed to radio waves.