Assessment of the general clinical condition and functional properties of the eyes of rabbits after THz irradiation.

THz radiation is increasingly used for diagnostics in medicine. As technology utilizing THz radiation continues to develop rapidly, it is becoming increasingly important to consider its biological effects and establish safe exposure standards and parameters. The paper presents data on the clinical status and functional properties of the anterior and posterior structures of the eyes of rabbits after THz irradiation at the frequency of 2.3 THz. Terahertz radiation was generated at Novosibirsk Free Electron Laser (NovoFEL) at "Siberian Synchrotron and Terahertz Radiation Centre" (Budker Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia). The exposure durations used were 15 and 30 minutes. Intensity ranges were I1=0.012 mW/cm, I2=0.018 mW/cm, and I3=0.024 mW/cm. The study investigated the effects of various time and power irradiation protocols on the California rabbit's eyes and after a period of one month, but no significant clinical or functional alterations were observed in response to the established intensity protocols. However, the study identified statistically significant changes in corneal hydration and endothelial cell density over time, particularly under protocols with 15- and 30-minute exposures. A negative correlation was found between endothelial cell density and corneal thickness (r=-0.36, p=0.042), suggesting that a reduction in the endothelial cell pool may be associated with increased corneal thickness. These changes were subclinical and did not lead to clinically significant pathological changes in the cornea. There were no signs of ASOCT (anterior segment-optical coherence tomography) hyperreflectivity. THz radiation with parameters listed above of 2.3 THz and an intensities of 0.012-0.024 mW/cm for 30 minutes has been shown to be conditionally safe for the structures of the rabbit eye. However, the detected subclinical corneal changes require further study to determine safe exposure limits.