Exposure to ionizing radiation (IR) could affect the human brain and eyes leading to both cognitive and visual impairments. The aim of this paper was to review and analyze the current literature, and to comment on the ensuing findings in the light of our personal contributions in this field. The review was carried out according to the PRISMA guidelines by searching PubMed, Scopus, Embase, PsycINFO and Google Scholar English papers published from January 2000 to January 2020. The results showed that prenatally or childhood-exposed individuals are a particular target group with a higher risk for possible radiation effects and neurodegenerative diseases. In adulthood and medical/interventional radiologists, the most frequent IR-induced ophthalmic effects include cataracts, glaucoma, optic neuropathy, retinopathy and angiopathy, sometimes associated with specific neurocognitive deficits. According to available information that eye alterations may induce or may be associated with brain dysfunctions and vice versa, we propose to label this relationship “eye-brain axis”, as well as to deepen the diagnosis of eye pathologies as early and easily obtainable markers of possible low dose IR-induced brain damage.

Background.Exposure to ionizing radiation could affect the brain and eyes leading to cognitive and vision impairment, behavior disorders and performance decrement during professional irradiation at medical radiology, including interventional radiological procedures, long-term space flights, and radiation accidents. Objective. The objective was to analyze the current experimental, epidemiological, and clinical data on the radiation cerebro-ophthalmic effects. Materials and methods. In our analytical review peer-reviewed publications via the bibliographic and scientometric bases PubMed / MEDLINE, Scopus, Web of Science, and selected papers from the library catalog of NRCRM – the leading institution in the field of studying the medical effects of ionizing radiation – were used. Results. The probable radiation-induced cerebro-ophthalmic effects in human adults comprise radiation cataracts, radiation glaucoma, radiation-induced optic neuropathy, retinopathies, angiopathies as well as specific neurocognitive deficit in the various neuropsychiatric pathology including cerebrovascular pathology and neurodegenerative diseases. Specific attention is paid to the likely stochastic nature of many of those effects. Those prenatally and in childhood exposed are a particular target group with a higher risk for possible radiation effects and neurodegenerative diseases. Conclusions. The experimental, clinical, epidemiological, anatomical and pathophysiological rationale for visual system and central nervous system (CNS) radiosensitivity is given. The necessity for further international studies with adequate dosimetric support and the follow-up medical and biophysical monitoring of high radiation risk cohorts is justified. The first part of the study currently being published presents the results of the study of the effects of irradiation in the participants of emergency works at the Chornobyl Nuclear Power Plant (ChNPP). Key words: ionizing radiation, cerebroophthalmic effects, neurocognitive deficit, radiation accident, radiation cataracts, macular degeneration.

Background. Ionizing radiation (IR) can affect the brain and the visual organ even at low doses, while provoking cognitive, emotional, behavioral, and visual disorders. We proposed to consider the brain and the visual organ as potential targets for the influence of IR with the definition of cerebro-ophthalmic relationships as the «eye-brain axis». Objective. The present work is a narrative review of current experimental, epidemiological and clinical data on radiation cerebro-ophthalmic effects in children, individuals exposed in utero, astronauts and interventional radiologists. Materials and methods. The review was performed according to PRISMA guidelines by searching the abstract and scientometric databases PubMed/MEDLINE, Scopus, Web of Science, Embase, PsycINFO, Google Scholar, published from 1998 to 2021, as well as the results of manual search of peer-reviewed publications. Results. Epidemiological data on the effects of low doses of IR on neurodevelopment are quite contradictory, while data on clinical, neuropsychological and neurophysiological on cognitive and cerebral disorders, especially in the left, dominant hemisphere of the brain, are nore consistent. Cataracts (congenital – after in utero irradiation) and retinal angiopathy are more common in prenatally-exposed people and children. Astronauts, who carry out longterm space missions outside the protection of the Earth’s magnetosphere, will be exposed to galactic cosmic radiation (heavy ions, protons), which leads to cerebro-ophthalmic disorders, primarily cognitive and behavioral disorders and cataracts. Interventional radiologists are a special risk group for cerebro-ophthalmic pathology – cognitive deficits, mainly due to dysfunction of the dominant and more radiosensitive left hemisphere of the brain, and cataracts, as well as early atherosclerosis and accelerated aging. Conclusions. Results of current studies indicate the high radiosensitivity of the brain and eye in different contingents of irradiated persons. Further research is needed to clarify the nature of cerebro-ophthalmic disorders in different exposure scenarios, to determine the molecular biological mechanisms of these disorders, reliable dosimetric support and taking into account the influence of non-radiation risk factors. Key words: ionizing radiation, brain, eye, cerebro-ophthalmic effects, radiation emergencies, prenatal irradiation, space flights, interventional radiology.

One of the current problems of modern radiobiology is determine the characteristics of the manifestation of radiation-induced effects not only at different dose loads, but also at different stages of development of the organism. In previous reports, we have summarized available evidence that at certain ages there is a comparative acceleration of radiation-induced pathological changes in the eye and brain, and the study and assessment of the risk of possible ophthalmic and neurological pathology in remote periods after contamination of radioactive areas. Data of irradiated in utero individuals are possible on the basis of observation of the state of the visual analyzer in persons who underwent intrauterine irradiation in 1986. Therefore, a parallel study of retinal morphometric parameters, amplitude and latency of components of evoked visual potentials in irradiated in utero individuals was performed. Objective: to evaluate the retinal morphometric parameters, amplitude and latency components of the evoked visual potentials in intrauterine irradiated persons. Materials and methods. The results of surveys of 16 people irradiated in utero in the aftermath of the Chornobyl disaster were used; the comparison group were residents of Kyiv of the corresponding age (25 people). Optical coherence tomography was performed on a Cirrus HD-OCT, Macular Cube 512x128 study technique was used. At the same time, the study of visual evoked potentials on the inverted pattern was performed, and occipital leads were analyzed. Visual evoked potentials were recorded on a reversible chess pattern (VEP) – an electrophysiological test, which is a visual response to a sharp change in image contrast when presenting a reversible image of a chessboard. Results. In those irradiated in utero at the age of 22–25 years, there was a probable increase in retinal thickness in the fovea, there was a tendency to increase the thickness of the retina in the areas around the fovea. When recording visual evoked potentials on a reversible chess pattern in this group, there was a tendency to decrease the amplitudes of components (N75, P100, N145, P200) in the right and left parieto-occipital areas and asymmetric changes in latency of these components. Conclusions. Early changes of fovea recorded in OCT and decreasing amplitudes of components of visual evoked potentials on the reversible chess pattern at the age of 22–25 years may indicate a risk of development in patients irradiated in utero, early age-related macular degeneration, as well as increased risk and increased risk structures of the visual analyzer. Key words: induced visual potentials, optical coherence tomography, retina, agerelated macular degeneration, ion izing radiation, dose.