Radiation cataract

Comparison of pediatric lens scattered dose measurements between axial 40-mm and helical 160-mm detector width computed tomography scan modes

BACKGROUND

Reports comparing field lens doses between helical scans with a 40-mm detector width and axial scans with a 160-mm detector width using different computed tomography (CT) scanners are currently scarce.

OBJECTIVE

To compare scatter doses for lenses between a helical scan with a 40-mm detector width and an axial scan with a 160-mm detector width when using different CT scanners in the context of pediatric chest examinations.

MATERIALS AND METHODS

Two different CT machines were used: Revolution CT (GE Healthcare, Waukesha, WI) with a 256-row, 0.625-mm multidetector; and Aquilion ONE GENESIS Edition (Canon Medical Systems, Otawara, Japan) with a 320-row, 0.5-mm multidetector. Three pediatric anthropomorphic phantoms were used, with optically stimulated luminescence dosimeters (OSLDs) placed on the left and right lenses. The scatter dose values measured by the OSLDs were compared between a helical scan with a 40-mm detector width and an axial scan with a 160-mm detector width during pediatric chest CT examinations.

RESULTS

Median equivalent doses for the helical and axial scans were 0.12 and 0.12 mSv/mGy for the newborn, 0.17 and 0.16 mSv/mGy for the 1-year-old, and 0.18 and 0.15 mSv/mGy for the 5-year-old, respectively, when using the Revolution CT. With the Revolution CT, no significant differences were observed in the scatter doses between helical and axial scans in the newborn and 1-year-old phantoms. However, the lens scatter dose for the helical scan was approximately 20-35% higher than that for the axial scan in the 5-year-old phantom (P<0.01). The median equivalent doses of eye lenses for the helical and axial scans were 0.12 and 0.07 mSv/mGy for the newborn, 0.07 and 0.05 mSv/mGy for the 1-year-old, and 0.14 and 0.12 mSv/mGy for the 5-year-old, respectively, when using the Aquilion ONE. With the Aquilion ONE, lens scatter doses for the helical scan were approximately 70%, 40%, and 30% higher in the newborn, 1-year-old, and 5-year-old phantoms, respectively, than those for the axial scan (P<0.01).

CONCLUSIONS

When using the Aquilion ONE, lens scatter doses for the helical scan were significantly higher in all three phantoms than those for the axial scan. In contrast, when using the Revolution CT, the lens scatter dose for the helical scan was significantly higher in the 5-year-old phantom than that for the axial scan. These results suggest that although scattered doses may vary with respect to the CT scanner and body size, they are generally lower in the case of axial scans.

Assessing the Efficacy of RADPAD Protection Drape in Reducing Radiation Exposure to Operators in the Cardiac Catheterization Laboratory: A Systematic Review and Meta-Analysis

One of the leading environmental hazards, ionizing radiation, is linked to several detrimental health consequences in the body. RADPAD (Worldwide Innovations & Technologies, Inc., Kansas City, Kansas) is a sterile, lead-free, lightweight, disposable radiation protection shield. We conducted a systematic review and meta-analysis to determine the effectiveness of RADPAD protection drapes in the cardiac catheterization lab and how they can aid interventional cardiologists in becoming subjected to less scatter radiation. PubMed, Embase, and Google Scholar were searched for studies discussing the efficacy of RADPAD protection drapes in reducing radiation exposure to operators in the cardiac catheterization laboratory. A random-effects model was used to pool odds ratios (ORs) and 95% confidence intervals (CIs) for endpoints: primary operator exposure dose, dose area product (DAP), relative exposure, and screening time. Our analysis included 892 patients from six studies. Compared to the No-RADPAD group, primary operator exposure dose (E) was significantly lower in the RADPAD group (OR: -0.9, 95% CI: -1.36 to -0.43, I2 = 80.5%, p = 0.0001). DAP was comparable between both groups (OR: 0.008, 95% CI: -0.12 to -0.14, I2 = 0%, p = 0.9066). There was no difference in the relative exposure (E/DAP) (OR: -0.47, 95% CI: -0.96 to 0.02, I2 = 0%, p = 0.90) and screening time (OR: 0.13, 95% CI: 0.08 to 0.35, I2 = 0%, p = 0.22) between the two groups. The interventional cardiology laboratory is exposed to significantly less scatter radiation during procedures owing to the RADPAD protective drape. Consequently, all catheterization laboratories could be advised to employ RADPAD protective drapes.

Radiation cataract in Heterogeneous Stock mice after γ-ray or HZE ion exposure

Health effects of space radiation are a serious concern for astronauts on long-duration missions. The lens of the eye is one of the most radiosensitive tissues in the body and, therefore, ocular health risks for astronauts is a significant concern. Studies in humans and animals indicate that ionizing radiation exposure to the eye produces characteristic lens changes, termed "radiation cataract," that can affect visual function. Animal models of radiation cataractogenesis have previously utilized inbred mouse or rat strains. These studies were essential for determining morphological changes and dose-response relationships between radiation exposure and cataract. However, the relevance of these studies to human radiosensitivity is limited by the narrow phenotypic range of genetically homogeneous animal models. To model radiation cataract in genetically diverse populations, longitudinal cataract phenotyping was nested within a lifetime carcinogenesis study in male and female heterogeneous stock (HS/Npt) mice exposed to 0.4 Gy HZE ions (n = 609) or 3.0 Gy γ-rays (n = 602) and in unirradiated controls (n = 603). Cataractous change was quantified in each eye for up to 2 years using Merriam-Focht grading criteria by dilated slit lamp examination. Virtual Optomotry™ measurement of visual acuity and contrast sensitivity was utilized to assess visual function in a subgroup of mice. Prevalence and severity of posterior lens opacifications were 2.6-fold higher in HZE ion and 2.3-fold higher in γ-ray irradiated mice compared to unirradiated controls. Male mice were at greater risk for spontaneous and radiation associated cataracts. Risk for cataractogenesis was associated with family structure, demonstrating that HS/Npt mice are well-suited to evaluate genetic determinants of ocular radiosensitivity. Last, mice were extensively evaluated for cataract and tumor formation, which revealed an overlap between individual susceptibility to both cancer and cataract.

The Impact of Robotic Fractionated Radiotherapy for Benign Tumors of Parasellar Region on the Eye Structure and Function

PURPOSE

To evaluate the radiation effect of fractionated robotic radiotherapy of benign tumors located in the parasellar region on the anterior and posterior segments of the eye.

METHODS

A prospective observational study based on the expanded ophthalmological examination. The pre-treatment baseline was used as a control for the post-radiotherapy follow-up examinations. The study group consists of 34 patients (68 eyes) irradiated using the CyberKnife system. There were ten patients with cavernous sinus meningioma, nine with pituitary adenoma, five with meningioma of the anterior and middle cranial fossa, five with meningioma in the region close to optic chiasm, three with craniopharyngioma, and two with meningioma of the orbit. All patients were treated using three fractions of 600-800 cGy. We assessed the impact of radiation on the eye based on changes in anatomical and functional features. The condition of the eye surface, central corneal thickness (CCT), endothelial cell density (ECD), lens densitometry, central macular thickness (CMT), and retinal nerve fiber layer (RNFL) were the anatomical features assessed. The functional tests were best-corrected visual acuity (BCVA), intraocular pressure (IOP), visual field (VF) and visual-evoked potentials (VEP). An ophthalmologic examination was performed before and 6, 12, 18, and 24 months after radiotherapy.

RESULTS

We did not observe any significant changes in BCVA, IOP, CCT, CMT, VF, and VEP, nor in the slit-lamp examination during the two-years observation. We found a significant decrease in ECD at all follow-up measurements. The drop in ECD exceeded approximated age-related physiological loss. The reduction in ECD was not large enough to disrupt corneal function and thus affect vision. We also observed a statistically significant reduction of RNFL in all observation time points. However, there was no correlation between the dose delivered to the optic pathway and the decrease in RNFL thickness. The thinning of the RNFL was not significant enough to impair visual function.

CONCLUSION

Fractionated robotic radiotherapy of the tumors located close to the optical pathway is safe and does not impair patient's vision. Minor changes found in optic nerve anatomy (RNFL thinning) might be related to radiation effect or tumor compression. The causal relation between low doses of radiation delivered to the cornea and the observed significant but slight decrease in ECD is uncertain. The observed changes did not cause visual disturbances perceivable by the patients.

Insights into the biochemical and biophysical mechanisms mediating the longevity of the transparent optics of the eye lens

In the human eye, a transparent cornea and lens combine to form the "refracton" to focus images on the retina. This requires the refracton to have a high refractive index "n," mediated largely by extracellular collagen fibrils in the corneal stroma and the highly concentrated crystallin proteins in the cytoplasm of the lens fiber cells. Transparency is a result of short-range order in the spatial arrangement of corneal collagen fibrils and lens crystallins, generated in part by post-translational modifications (PTMs). However, while corneal collagen is remodeled continuously and replaced, lens crystallins are very long-lived and are not replaced and so accumulate PTMs over a lifetime. Eventually, a tipping point is reached when protein aggregation results in increased light scatter, inevitably leading to the iconic protein condensation-based disease, age-related cataract (ARC). Cataracts account for 50% of vision impairment worldwide, affecting far more people than other well-known protein aggregation-based diseases. However, because accumulation of crystallin PTMs begins before birth and long before ARC presents, we postulate that the lens protein PTMs contribute to a "cataractogenic load" that not only increases with age but also has protective effects on optical function by stabilizing lens crystallins until a tipping point is reached. In this review, we highlight decades of experimental findings that support the potential for PTMs to be protective during normal development. We hypothesize that ARC is preventable by protecting the biochemical and biophysical properties of lens proteins needed to maintain transparency, refraction, and optical function.

Radiation induced cataracts in interventionalists occupationally exposed to ionising radiation

BACKGROUND

Occupational exposure to ionising radiation may have detrimental health effects. Longer and more complex fluoroscopic procedures have placed interventionalists at increased occupational health risks especially for developing cataracts in the radiosensitive lenses of the eyes.

OBJECTIVES

This study aimed to determine the prevalence of occupational related cataracts and describe the risk factors for cataracts in occupationally exposed interventionalists compared with unexposed doctors.

METHOD

A cross-sectional study using multiple methods. A survey was conducted. The radiation workload was determined based on a self-administered questionnaire and dose area product values determined in previous studies. Both groups had slit lamp examinations. The data were analysed analytically using R software version 9.3.

RESULTS

The study included 98 interventionalists. The combined prevalence of posterior sub-capsular (PSC) and cortical cataracts was 18.8% in the exposed and 13.9% in the unexposed group. The prevalence of PSC cataracts in the exposed group was 5.9% and 2.8% in the unexposed group, with an odds ratio (OR) of 2.2 (95% confidence interval [CI]: 0.58; 8.61). Posterior sub-capsular cataracts were more common in the left eye. The increase in cataracts was not statistically significant in the exposed group but is of clinical significance.

CONCLUSION

The findings are important as they highlight the need for greater vigilance for protecting the radiation healthcare workforce in a developing country setting.

CONTRIBUTION

The research is the first of its kind in South Africa and Africa and contributes to determining the prevalence in this highly skilled and occupationally vulnerable group.

Prospective Study of 4 Gy Radiotherapy for Orbital Mucosa-Associated Lymphoid Tissue Lymphoma (FORMAL)

Simple Summary

Marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALToma) is a slow-growing lymphoma with a good prognosis. This study was designed to evaluate the effectiveness of radiotherapy at a very low dose of 4 Gy (2 Gy × 2 fractions) in stage I orbital MALToma. Patients with complete remission after a very low dose of 4 Gy (2 Gy × 2 fractions) radiotherapy were closely monitored, and those who did not achieve remission received an additional 24 Gy radiotherapy. Using 4 Gy radiotherapy for orbital MALToma, 11 out of 17 lesions achieved complete remission. There was no transformation of diffuse large B-cell lymphoma, and there was only one local failure. Radiation therapy at a low dose of 4 Gy could be performed effectively and safely with a planned second-line treatment.

Abstract

External beam radiotherapy is effective for stage I orbital mucosa-associated lymphoid tissue lymphoma (MALToma). Hence, very-low-dose radiotherapy is increasingly being investigated. We conducted a single-center prospective phase II trial to evaluate the effectiveness of very-low-dose radiotherapy of 4 Gy (2 Gy × 2 fractions) in pathologically confirmed stage I orbital MALToma. In this first prospective trial, patients with complete response were observed after 3–6 months of follow-up. For patients without complete remission, a radiation dose of 24 Gy/12 fractions was additionally delivered. The primary endpoint was complete response rate; secondary endpoints were overall survival, local control, and progression-free survival. Seventeen patients were screened and three patients refused enrollment during October 2018–October 2021. Thus, 14 patients (17 eyes) were analyzed (median follow-up, 28.2 months). The overall response rate was 100% (complete remission: 11 lesions; partial remission: six lesions). In all lesions with residual disease, additional radiation therapy (dose: 24 Gy) was performed. One local failure was observed. Therefore, 4 Gy ultralow-dose radiation therapy for orbital MALToma was safely performed with a planned second-line treatment in patients without complete remission. This is the first prospective study to report the effectiveness of ultralow-dose radiotherapy of 4 Gy for stage I orbital MALToma treatment.

Impact of the incorrect use of lead drapes on staff and patient doses in interventional radiology

To evaluate the usefulness of commercially available scatter reduction drapes in mitigating staff exposure in interventional radiology and the potential harmful effects of drape malpositioning in terms of exposure levels to both patients and staff. An anthropomorphic phantom was irradiated on an angiography device under three scenarios: no drape and correct and incorrect drape positioning. Different levels of incorrect drape positioning relative to the field-of-view (FOV) were evaluated: slight, mild and severe. Real-time dosimeter systems (positioned on the operator's eye, chest and thyroid) were used to evaluate accumulative doses and dose rates. Different obstruction levels were evaluated and compared to the observer's perception. Additionally, patient exposure was evaluated for all scenarios using a dose area product (DAP). Up to a mild obstruction, by using the drape a dose reduction of up to 86% was obtained while a severe obstruction produced a 1000% increase in exposure, respectively for all dosimeter positions compared to the use of no drape. A similar order of magnitude was observed for patient exposure. Good agreement was obtained for the observer perception of the FOV obstruction up to 25% of the FOV; for larger obstructions, an overestimate of the obstruction was observed. Patient lead drapes can reduce staff doses in interventional radiology procedures even when mildly malpositioned and obscuring the FOV. Special attention to protective drape positioning is necessary, since the severe obstruction of the FOV results in a large increase in both operator and patient exposure.

Fluoroless endourological surgery for high burden renal and proximal ureteric stones: A safe technique for experienced surgeons

Objective: To describe the feasibility of treating proximal ureteric and renal stones using flexible ureteroscopy (fURS) or a double approach (mini-percutaneous nephrolithotomy [PCNL] + fURS) without any use of radiation.

Patients and methods: We retrospectively reviewed the data of all patients operated by one surgeon for retrograde endoscopic removal of renal and ureteric lithiasis performed between June 2015 and January 2019 in our institution. Patients with anatomical complexities, high-burden stone disease (diameter >20 mm), and medical comorbidities (anti-platelet drug administration) were included in our study. Outcomes analysed included complication rate, stone-free rate (SFR, defined as no residual stone >1 mm), and repeat procedure rate.

Results: In all, 183 consecutive URS for proximal ureteric and renal lithiasis were conducted. C-arm fluoroscope guidance was not required, not even in the complex cases. Simultaneous ultrasonography and fURS guidance was used in patients where the mini-PCNL approach was indicated. Lead aprons were not needed by the operating room staff in any of the operations. The SFR was 91.8% after the first procedure, with no Clavien–Dindo Grade III or IV complications.

Conclusion: Our present series shows clearly that the fURS and mini-PCNL approach under fURS control is a feasible and safe technique for experienced surgeons. Patients had a high SFR and no technique-related complications, with no additional risk of X-ray exposure. However, a prospective study is required to test the reproducibility of this technique.

Abbreviations: GMSV: Galdakao-modified supine Valdivia; ICRP: International Commission on Radiological Protection; KUB: plain abdominal radiograph of the kidneys, ureters and bladder; OR: operating room; PCNL: percutaneous nephrolithotomy; SFR: stone-free rate; UAS: ureteric access sheath; (f)URS: (flexible) ureteroscopy; US: ultrasonography

High Incidence of Cataracts in the Follow-Up of Patients Undergoing Percutaneous Coronary Intervention for Chronic Coronary Total Occlusion

Development of cataracts is a well-known adverse effect of ionizing radiation, but little information is available on their incidence in patients after other medical procedures, such as cardiac catheterizations. The study objective was to determine the incidence of cataracts in a cohort of patients undergoing percutaneous coronary intervention (PCI) for chronic coronary total occlusion (CTO) and its association with radiation dose. The study analyzed the incidence of cataracts during the follow-up of 126 patients who underwent chronic total coronary PCI, using Cox regression to identify predictive factors of cataract development. The study included 126 patients, 86.9% male, with a mean age of 60.5 years (range, 55.0-68.0 years). Twenty-three (18.2% n = 23) developed cataracts during a mean follow-up of 49.5 months (range 37.3-64.5 months). A higher incidence was observed in patients who received more than 5 Gy (29.0% vs. 14.7%, Hazard ratio (HR = 2.84 [1.19-6.77]). Multivariate analysis revealed a relationship between cataract development during the follow-up and a receipt of radiation dose >5 Gy (HR = 2.60, 95% confidence interval [CI 1.03-6.61]; p = 0.03), presence or history of predisposing eye disease (HR = 4.42, CI:1.57-12.40), diabetes (HR = 3.33 [1.22-9.24]), and older age, as in >57 (HR, 6.40 [1.81-22.61]). An elevated incidence of cataracts was observed in patients after PCI for CTO. The onset of cataracts is related to the radiation dose during catheterization, which is a potentially avoidable effect of which operators should be aware.

Influence of eye movement on lens dose and optic nerve target coverage during craniospinal irradiation

Purpose

Optic nerves are part of the craniospinal irradiation (CSI) target volume. Modern radiotherapy techniques achieve highly conformal target doses while avoiding organs-at-risk such as the lens. The magnitude of eye movement and its influence on CSI target- and avoidance volumes are unclear. We aimed to evaluate the movement-range of lenses and optic nerves and its influence on dose distribution of several planning techniques.

Methods

Ten volunteers underwent MRI scans in various gaze directions (neutral, left, right, cranial, caudal). Lenses, orbital optic nerves, optic discs and CSI target volumes were delineated. 36-Gy cranial irradiation plans were constructed on synthetic CT images in neutral gaze, with Volumetric Modulated Arc Therapy, pencil-beam scanning proton therapy, and 3D-conventional photons. Movement-amplitudes of lenses and optic discs were analyzed, and influence of gaze direction on lens and orbital optic nerve dose distribution.

Results

Mean eye structures' shift from neutral position was greatest in caudal gaze; -5.8±1.2 mm (±SD) for lenses and 7.0±2.0 mm for optic discs. In 3D-conventional plans, caudal gaze decreased Mean Lens Dose (MLD). In VMAT and proton plans, eye movements mainly increased MLD and diminished D98 orbital optic nerve (D98_OON) coverage; mean MLD increased up to 5.5 Gy [total ΔMLD range -8.1 to 10.0 Gy], and mean D98_OON decreased up to 3.3 Gy [total ΔD98_OON range -13.6 to 1.2 Gy]. VMAT plans optimized for optic disc Internal Target Volume and lens Planning organ-at-Risk Volume resulted in higher MLD over gaze directions. D98_OON became ≥95% of prescribed dose over 95/100 evaluated gaze directions, while all-gaze bilateral D98_OON significantly changed in 1 of 10 volunteers.

Conclusion

With modern CSI techniques, eye movements result in higher lens doses and a mean detriment for orbital optic nerve dose coverage of <10% of prescribed dose.

Are X-ray Safety Glasses Alone Enough for Adequate Ocular Protection in Complex Radiological Interventions?

ABSTRACT

The maximum annual radiation ocular dose limit for medical staff has been reduced to 20 mSv in the current European directive 2013/59/Euratom. This multi-centric study aims at reporting the protected and unprotected eye lens doses in different fluoroscopically guided interventions and to evaluate any other factors that could influence the ocular dose. From July 2018 to July 2019, ocular radiation doses of six interventionists of four departments during complex interventions were recorded with a thermoluminescent dosimeter in front of and behind radiation protection glasses to measure the protected and unprotected doses. The position of personnel, intervention type, fluoroscopy time, total body dose and use of pre-installed protection devices like lead acrylic shields were also systematically recorded. Linear regression analysis was used to estimate the doses at 2 y and 5 y. The annual unprotected/protected ocular doses of six interventionists were 67/21, 32.7/3.3, 27.4/5.1, 7/0, 21.8/2.2, and 0/0 mSv, respectively. The unprotected dose crossed the 20-mSv annual limits for four interventionists and protected dose for one less experienced interventionist. The estimated 5-y protected ocular dose of this interventionist was 101.318 mSv (95%CI 96.066-106.57), also crossing the 5-y limit. The use of a lead acrylic shield was observed to have a significant effect in reducing ocular doses. The annual unprotected and protected ocular doses for interventionists dealing with complex interventions could cross the present permitted yearly limit. The measurement of significant protected ocular dose behind the radiation protection glasses emphasizes the additional indispensable role of pre-installed radiation protection devices and training in reducing radiation doses for complex procedures.

Outcome of cataract surgery in children affected by malignancies other than retinoblastoma with eye-lens radiation exposure

PURPOSE

To describe, retrospectively, the visual outcome, feasibility, and safety of cataract surgery in a pediatric population affected by iatrogenic cataract, secondary to systemic oncological treatment for malignancies other than retinoblastoma.

METHODS

Young patients, affected by radiation-induced cataract, who were referred to the San Paolo Ophthalmic Center in Padova between 2010 and 2017, were included in the study. All patients had previously received radiotherapy and/or chemotherapy treatment for malignancies, between 2004 and 2013. All medical records of infants who underwent cataract surgery were accurately reviewed.

RESULTS

Eighteen eyes out of 11 patients included in the study underwent cataract surgery. The mean age at surgery was 9.7 ± 3.6 years. The interval between tumor diagnosis and cataract development was around 3 years. Mean follow-up after surgery was 15.4 ± 6.3 months. All eyes underwent posterior chamber intraocular lens implantation, posterior capsulotomy, and anterior vitrectomy in one time surgery. No intraoperative complications were shown. Post-operatively, only one eye received laser capsulotomy due to posterior capsule opacification. At the end of follow up, best-corrected visual acuity was 20/20 (LogMAR 0) in all eyes and significantly improved (p < 0.01) compared to baseline.

CONCLUSIONS

Iatrogenic-cataract surgery in pediatric oncological patients is a safe and effective way to improve visual acuity. Posterior capsulotomy and anterior vitrectomy at the time of surgery reduce the rate of posterior lens opacification and guarantee an excellent visual acuity in these patients.

Posterior subcapsular cataracts are a late effect after acute exposure to 0.5 Gy ionizing radiation in mice

PURPOSE

The long-term effect of low and moderate doses of ionizing radiation on the lens is still a matter of debate and needs to be evaluated in more detail.

MATERIAL AND METHODS

We conducted a detailed histological analysis of eyes from B6C3F1 mice cohorts after acute gamma irradiation (60Co source; 0.063 Gy/min) at young adult age of 10 weeks with doses of 0.063, 0.125, and 0.5 Gy. Sham irradiated (0 Gy) mice were used as controls. To test for genetic susceptibility heterozygous Ercc2 mutant mice were used and compared to wild-type mice of the same strain background. Mice of both sexes were included in all cohorts. Eyes were collected 4 h, 12, 18 and 24 months after irradiation. For a better understanding of the underlying mechanisms, metabolomics analyses were performed in lenses and plasma samples of the same mouse cohorts at 4 and 12 h as well as 12, 18 and 24 months after irradiation. For this purpose, a targeted analysis was chosen.

RESULTS

This analysis revealed histological changes particularly in the posterior part of the lens that rarely can be observed by using Scheimpflug imaging, as we reported previously. We detected a significant increase of posterior subcapsular cataracts (PSCs) 18 and 24 months after irradiation with 0.5 Gy (odds ratio 9.3; 95% confidence interval 2.1-41.3) independent of sex and genotype. Doses below 0.5 Gy (i.e. 0.063 and 0.125 Gy) did not significantly increase the frequency of PSCs at any time point. In lenses, we observed a clear effect of sex and aging but not of irradiation or genotype. While metabolomics analyses of plasma from the same mice showed only a sex effect.

CONCLUSIONS

This article demonstrates a significant radiation-induced increase in the incidence of PSCs, which could not be identified using Scheimpflug imaging as the only diagnostic tool.

Safety profiles of terahertz scanning in ophthalmology

Terahertz (THz) technology has emerged recently as a potential novel imaging modality in biomedical fields, including ophthalmology. However, the ocular biological responses after THz electromagnetic exposure have not been investigated. We conducted a rabbit study to evaluate the safety profiles of THz scanning on eyes, at a tissue, cellular, structural and functional level. Eight animals (16 eyes) were analysed after excessive THz exposure (control, 1 h, 4 h, and 1 week after continuous 4-h exposure; THz frequency = 0.3 THz with continuous pulse generated at 40 µW). We found that at all the time points, the corneas and lens remained clear with no corneal haze or lens opacity formation clinically and histopathologically. No thermal effect, assessed by thermographer, was observed. The rod and cone cell-mediated electroretinography responses were not significantly altered, and the corneal keratocytes activity as well as endothelial viability, assessed by in-vivo confocal microscopy, was not affected. Post-exposed corneas, lens and retinas exhibited no significant changes in the mRNA expression of heat shock protein (HSP)90AB1), DNA damage inducible transcript 3 (DDIT3), and early growth response (EGR)1. These tissues were also negative for the inflammatory (CD11b), fibrotic (fibronectin and α-smooth muscle actin), stress (HSP-47) and apoptotic (TUNEL assay) responses on the immunohistochemical analyses. The optical transmittance of corneas did not change significantly, and the inter-fibrillar distances of the corneal stroma evaluated with transmission electron microscopy were not significantly altered after THz exposure. These results provide the basis for future research work on the development of THz imaging system for its application in ophthalmology.

Radiation-induced lens opacities: Epidemiological, clinical and experimental evidence, methodological issues, research gaps and strategy

In 2011, the International Commission on Radiological Protection (ICRP) recommended reducing the occupational equivalent dose limit for the lens of the eye from 150 mSv/year to 20 mSv/year, averaged over five years, with no single year exceeding 50 mSv. With this recommendation, several important assumptions were made, such as lack of dose rate effect, classification of cataracts as a tissue reaction with a dose threshold at 0.5 Gy, and progression of minor opacities into vision-impairing cataracts. However, although new dose thresholds and occupational dose limits have been set for radiation-induced cataract, ICRP clearly states that the recommendations are chiefly based on epidemiological evidence because there are a very small number of studies that provide explicit biological and mechanistic evidence at doses under 2 Gy. Since the release of the 2011 ICRP statement, the Multidisciplinary European Low Dose Initiative (MELODI) supported in April 2019 a scientific workshop that aimed to review epidemiological, clinical and biological evidence for radiation-induced cataracts. The purpose of this article is to present and discuss recent related epidemiological and clinical studies, ophthalmic examination techniques, biological and mechanistic knowledge, and to identify research gaps, towards the implementation of a research strategy for future studies on radiation-induced lens opacities. The authors recommend particularly to study the effect of ionizing radiation on the lens in the context of the wider, systemic effects, including in the retina, brain and other organs, and as such cataract is recommended to be studied as part of larger scale programs focused on multiple radiation health effects.

Radiation-Induced Cerebro-Ophthalmic Effects in Humans

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.

The Promise of Proton Therapy for Central Nervous System Malignancies

Radiation therapy plays a significant role in management of benign and malignant diseases of the central nervous system. Patients may be at risk of acute and late toxicity from radiation therapy due to dose deposition in critical normal structures. In contrast to conventional photon delivery techniques, proton therapy is characterized by Bragg peak dose deposition which results in decreased exit dose beyond the target and greater sparing of normal structure which may reduce the rate of late toxicities from treatment. Dosimetric studies have demonstrated reduced dose to normal structures using proton therapy as compared to photon therapy. In addition, clinical studies are being reported demonstrating safety, feasibility, and low rates of acute toxicity. Technical challenges in proton therapy remain, including full understanding of depth of proton penetration and the biological activity in the distal Bragg peak. In addition, longer clinical follow-up is required to demonstrate reduction in late toxicities as compared to conventional photon-based radiation techniques. In this review, we summarize the current clinical literature and areas of active investigation in proton therapy for adult central nervous system malignancies.

BRAIN AND EYE AS POTENTIAL TARGETS FOR IONIZING RADIATION IMPACT. Part І. THE CONSEQUENCES OF IRRADIATION OF THE PARTICIPANTS OF THE LIQUIDATION OF THE CHORNOBYL ACCIDENT

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, includinginterventional 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 - theleading 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 neurodegenerativediseases. Specific attention is paid to the likely stochastic nature of many of those effects. Those prenatally and inchildhood 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 visualsystem and central nervous system (CNS) radiosensitivity is given. The necessity for further international studieswith adequate dosimetric support and the follow-up medical and biophysical monitoring of high radiation riskcohorts is justified. The first part of the study currently being published presents the results of the study of theeffects of irradiation in the participants of emergency works at the Chornobyl Nuclear Power Plant (ChNPP).

Ophthalmic manifestations of ionising radiation among interventionalists

Background: Ionising radiation (IR) is an occupational hazard for interventionalists. Dry eye syndrome may develop. There may be damage to the corneal epithelium, causing irritation and ulceration. Radiation-induced cataracts commonly develop in the posterior sub-capsular (PSC) region of the lens and are more common in the left eye.Aim: The aim of this study was to describe the ophthalmological findings in South African interventionalists occupationally exposed to IR.Setting: This study was conducted in South Africa.Methods: A prospective cross-sectional study was conducted. Interventional radiologists (25), adult cardiologists (42) and paediatric cardiologists (31) were recruited at conferences and included in the study. Convenience sampling was used. Participants completed a survey that collected data on their demographics, their cataract risk factors and co-morbid diseases, their occupational history, their radiation safety practices and their training in occupational history. Participants’ eyes were examined using a slit lamp after dilation of the eyes. Ethics clearance was obtained and each participant gave informed consent. A descriptive analysis was done.Results: The median age of the 98 interventionalists screened was 43.5 years. They worked with radiation for a median of 7.5 years. Cataracts occurred in the left eye of 17 (17.3%) participants and in the right eye of nine (9.2%). There were five (5.1%) PSC cataracts in the left eye and one (1%) in the right eye. The vitreous was abnormal in 19.4% of participants. The tear break-up time was abnormal in 48% of participants.Conclusion: Ionising radiation is an occupational hazard posing a risk to interventionalists’ eyes. They are at increased risk of cataracts and dry eye syndrome, which can affect their occupational performance and quality of life. Education can positively influence the radiation safety practices of interventionalists that could reduce the detrimental effects of IR on their eyes.

Cataract risk in US radiologic technologists assisting with fluoroscopically guided interventional procedures: a retrospective cohort study

OBJECTIVES

To assess radiation exposure-related work history and risk of cataract and cataract surgery among radiologic technologists assisting with fluoroscopically guided interventional procedures (FGIP).

METHODS

This retrospective study included 35 751 radiologic technologists who reported being cataract-free at baseline (1994-1998) and completed a follow-up questionnaire (2013-2014). Frequencies of assisting with 21 types of FGIP and use of radiation protection equipment during five time periods (before 1970, 1970-1979, 1980-1989, 1990-1999, 2000-2009) were derived from an additional self-administered questionnaire in 2013-2014. Multivariable-adjusted relative risks (RRs) for self-reported cataract diagnosis and cataract surgery were estimated according to FGIP work history.

RESULTS

During follow-up, 9372 technologists reported incident physician-diagnosed cataract; 4278 of incident cases reported undergoing cataract surgery. Technologists who ever assisted with FGIP had increased risk for cataract compared with those who never assisted with FGIP (RR: 1.18, 95% CI 1.11 to 1.25). Risk increased with increasing cumulative number of FGIP; the RR for technologists who assisted with >5000 FGIP compared with those who never assisted was 1.38 (95% CI 1.24 to 1.53; p trend <0.001). These associations were more pronounced for FGIP when technologists were located ≤3 feet (≤0.9 m) from the patient compared with >3 feet (>0.9 m) (RRs for >5000 at ≤3 feet vs never FGIP were 1.48, 95% CI 1.27 to 1.74 and 1.15, 95% CI 0.98 to 1.35, respectively; pdifference=0.04). Similar risks, although not statistically significant, were observed for cataract surgery.

CONCLUSION

Technologists who reported assisting with FGIP, particularly high-volume FGIP within 3 feet of the patient, had increased risk of incident cataract. Additional investigation should evaluate estimated dose response and medically validated cataract type.

Are orthopedic surgeons exposed to excessive eye irradiation? A prospective study of lens irradiation in orthopedics and traumatology

INTRODUCTION

Numerous studies in recent years highlighted an increased risk of pathologies related to ionizing radiation in caregivers. A new French decree was adopted on June 4, 2018, dividing by 7.5 the radiation dose authorized in the lens for exposed workers.

HYPOTHESIS

The hypothesis of the present study was that ocular irradiation in orthopedic surgeons was below the new legal threshold.

METHOD

The equivalent dose (mSv) received by the lens was prospectively assessed in 10 orthopedic surgeons (5 senior, 5 residents), using 3 passive dosimeters placed at the forehead and either temple. Each intervention of each operator was recorded, with dose per area in the operating room at each use of the fluoroscope.

RESULTS

All equivalent doses to the lens at the end of the 4 month study period were well below threshold. Doses were not significantly different between forehead and either temple (p=0.7, p=0.6 for the 2 temples). There was no difference according to side of the head (p=0.3). The dose received in the lens correlated with the dose delivered in the room (p=0.004). There were no significant differences in irradiation according to the surgeon's experience (p=0.2) or trauma activity rate (p=0.4).

DISCUSSION

No studies have reported equivalent doses to the lens exceeding the authorized limit. But none previously measured equivalent dose to the lens according to the axis of irradiation in the eyes. The present study showed that orthopedic surgeons received as much eye radiation laterally as frontally. Ocular radiation protection needs therefore to be as effective laterally as frontally. The surgeon's experience did not emerge as a protective factor against ocular irradiation.

Compliance With Radiation Protection Practices Among Radiologists

BACKGROUND

Radiologists are at higher risk of adverse health effects due to their occupational radiation exposure; therefore, applying protection techniques is imperative. Studies on radiologists' compliance in this regard are scarce. We aimed to assess compliance with radiation safety practices among radiologists.

METHODS

Questionnaires were distributed to radiologists in tertiary hospitals. The questionnaire was designed to assess compliance in three domains: using personal protective devices, using exposure-reduction techniques during fluoroscopic exposures, and using personal dose-monitoring devices. Descriptive analysis of the compliance was performed.

RESULTS

Sixty-two radiologists were included in the analysis. Use of leaded aprons and thyroid shields was commonplace, whereas only 3.2% ever use leaded eyeglasses. About half of the radiologists always considered reducing the time of exposure and avoided exposure by the primary beam, and the other half did that sometimes. Most of the radiologists (66.1%) always complied with reducing the number of unnecessary exposures, and the rest only complied sometimes. Most of the radiologists (93.5%) always used single personal dose-monitoring devices, most commonly at the neck level over the collar. There was no difference in compliance between different sexes, position descriptions, hospital types, hospital sizes, or years of experience.

CONCLUSION

Future compliance improvement strategies for radiologists should focus on use of thyroid shields and leaded eyeglasses and use of exposure-reduction techniques during fluoroscopic operations.

Radiation dose constraints for organs at risk in neuro-oncology; the European Particle Therapy Network consensus

PURPOSE

For unbiased comparison of different radiation modalities and techniques, consensus on delineation of radiation sensitive organs at risk (OARs) and on their dose constraints is warranted. Following the publication of a digital, online atlas for OAR delineation in neuro-oncology by the same group, we assessed the brain OAR-dose constraints in a follow-up study.

METHODS

We performed a comprehensive search to identify the current papers on OAR dose constraints for normofractionated photon and particle therapy in PubMed, Ovid Medline, Cochrane Library, Embase and Web of Science. Moreover, the included articles' reference lists were cross-checked for potential studies that met the inclusion criteria. Consensus was reached among 20 radiation oncology experts in the field of neuro-oncology.

RESULTS

For the OARs published in the neuro-oncology literature, we summarized the available literature and recommended dose constraints associated with certain levels of normal tissue complication probability (NTCP) according to the recent ICRU recommendations. For those OARs with lacking or insufficient NTCP data, a proposal for effective and efficient data collection is given.

CONCLUSION

The use of the European Particle Therapy Network-consensus OAR dose constraints summarized in this article is recommended for the model-based approach comparing photon and proton beam irradiation as well as for prospective clinical trials including novel radiation techniques and/or modalities.

The clinical features of radiation cataract in patients with ocular adnexal mucosa-associated lymphoid tissue lymphoma

BACKGROUND

To examine the clinical features of radiation cataract in patients with ocular adnexal mucosa-associated lymphoid tissue (MALT) lymphoma.

METHODS

Twenty-one patients with 26 eyes diagnosed with ocular adnexal MALT lymphoma (26 eyes), who were treated in Hokkaido University Hospital, were retrospectively reviewed based on medical records.

RESULTS

Out of the 21 patients, 16 patients (21 eyes) received radiation therapy (RT) with a total dose of 30 Gy. All cases eventually achieved complete remission. Eight of these patients (11 eyes: 52.3%) required cataract surgery after RT. The mean age at surgery was 56.8 (40-70) years. The mean latency between RT and the indication for surgery was 43.3 months. The percentage of females was significantly higher in patients who required surgery (P < 0.01), compared with those without surgery. The eyes of patients who received bolus technique on radiation treatment developed cataract more frequently (P < 0.05). In contrast, none of the patients without RT required cataract surgery.

CONCLUSIONS

Patients with ocular adnexal MALT lymphoma who underwent surgery for radiation cataract were seen more often in relatively young, female patients, and surgery was required about 3 years after RT. A long-term observation may be needed for patients after RT for a tumor. A female sex and the bolus technique may be risk factors for radiation cataract.

Modifiers of radiation effects in the eye

World events, including the threat of radiological terrorism and the fear of nuclear accidents, have highlighted an urgent need to develop medical countermeasures to prevent or reduce radiation injury. Similarly, plans for manned spaceflight to a near-Earth asteroid or journey to Mars raise serious concerns about long-term effects of space radiation on human health and the availability of suitable therapeutic interventions. At the same time, the need to protect normal tissue from the deleterious effects of radiotherapy has driven considerable research into the design of effective radioprotectors. For more than 70 years, animal models of radiation cataract have been utilized to test the short and long-term efficacy of various radiation countermeasures. While some compounds, most notably the Walter Reed (WR) class of radioprotectors, have reported limited effectiveness when given before exposure to low-LET radiation, the human toxicity of these molecules at effective doses limits their usefulness. Furthermore, while there has been considerable testing of eye responses to X- and gamma irradiation, there is limited information about using such models to limit the injurious effects of heavy ions and neutrons on eye tissue. A new class of radioprotector molecules, including the sulfhydryl compound PrC-210, are reported to be effective at much lower doses and with far less side effects. Their ability to modify ocular radiation damage has not yet been examined. The ability to non-invasively measure sensitive, radiation-induced ocular changes over long periods of time makes eye models an attractive option to test the radioprotective and radiation mitigating abilities of new novel compounds.

A multiple methods approach: radiation associated cataracts and occupational radiation safety practices in interventionalists in South Africa

Ionising radiation is a modality used in diagnostic and therapeutic medicine. The technology has improved and resulted in lower dose exposure but there has been an escalation in the quantity of procedures, their duration and complexity. These factors have meant increased occupational radiation exposure for interventionalists. Ionising radiation exposure can have detrimental health effects and includes radiation skin burns, various carcinomas, genetic and chromosomal aberrations and cataractogenesis of the lenses of the eye. The lenses of the eye are of the most radiosensitive organs and the risk of cataracts is high despite low radiation dose exposures. The use of personal protective equipment (PPE) is a method that can be used to mitigate the risk for developing lens opacifications. The consistent and effective utilisation of PPE is marred by availability, proper fit and ease of use when performing procedures. Radiation safety training is imperative to enforce a culture of radiation safety among interventionalists. The aim of this study was to quantify and describe cataracts among South African interventionalists and to understand their radiation safety practices. For this purpose, a cross sectional study was designed using multiple methods. A survey was conducted to determine the demographics and the risk factors of doctors exposed to radiation to doctors not exposed. The radiation workload and radiation safety practices of interventionalists were explored. Both groups had slit lamp examinations. The data were analysed analytically and a regression model developed looking at the outcomes and the risk factors. Qualitative in-depth interviews and group interviews were conducted to explore the perceptions of interventionalists regarding radiation safety. Deductive and inductive thematic analysis was done. Interdisciplinary research is challenging but offers tremendous opportunity for exploring and tackling complex issues related to securing a safe radiation work environment.

Comprehensive assessment of patient image quality and radiation dose in latest generation cardiac x-ray equipment for percutaneous coronary interventions

This study aimed to determine whether a reduction in radiation dose was found for percutaneous coronary interventional (PCI) patients using a cardiac interventional x-ray system with state-of-the-art image enhancement and x-ray optimization, compared to the current generation x-ray system, and to determine the corresponding impact on clinical image quality. Patient procedure dose area product (DAP) and fluoroscopy duration of 131 PCI patient cases from each x-ray system were compared using a Wilcoxon test on median values. Significant reductions in patient dose ([Formula: see text]) were found for the new system with no significant change in fluoroscopy duration ([Formula: see text]); procedure DAP reduced by 64%, fluoroscopy DAP by 51%, and "cine" acquisition DAP by 76%. The image quality of 15 patient angiograms from each x-ray system (30 total) was scored by 75 clinical professionals on a continuous scale for the ability to determine the presence and severity of stenotic lesions; image quality scores were analyzed using a two-sample [Formula: see text]-test. Image quality was reduced by 9% ([Formula: see text]) for the new x-ray system. This demonstrates a substantial reduction in patient dose, from acquisition more than fluoroscopy imaging, with slightly reduced image quality, for the new x-ray system compared to the current generation system.

RADIATION PROTECTION IN AN INTERVENTIONAL LABORATORY: A COMPARATIVE STUDY OF AUSTRALIAN AND SAUDI ARABIAN HOSPITALS

This study aimed to investigate whether the use of protection devices and attitudes of interventional professionals (including radiologists, cardiologists, vascular surgeons, medical imaging technicians and nurses) towards radiation protection will differ between Saudi Arabian and Australian hospitals. Hard copies of an anonymous survey were distributed to 10 and 6 clinical departments in the Eastern province of Saudi Arabia and metropolitan hospitals in Western Australia, respectively. The overall response rate was 43 % comprising 110 Australian participants and 63 % comprising 147 Saudi participants. Analysis showed that Australian respondents differed significantly from Saudi respondents with respect to their usages of leaded glasses (p < 0.001), ceiling-suspended lead screen (p < 0.001) and lead drape suspended from the table (p < 0.001). This study indicates that the trained interventional professionals in Australia tend to adhere to benefit from having an array of tools for personal radiation protection than the corresponding group in Saudi Arabia.

AN ASSESSMENT OF THE DOSE REDUCTION OF COMMERCIALLY AVAILABLE LEAD PROTECTIVE GLASSES FOR INTERVENTIONAL RADIOLOGY STAFF

In light of the proposal from the International Commission on Radiological Protection for a lowered eye dose limit, now adopted by a European Union Council Directive, lead glasses may be required for some staff in interventional radiology to ensure that occupational exposure is as low as reasonably practicable. To investigate the lens protection offered from various models of lead glasses exposed to X-rays coming from a source to the left and below, calibrated radiochromic film was positioned in the lens area of a head phantom. When the source-to-eye angles were large, the dose reduction factors (the ratio of eye dose without protection to dose with protection) to the right lens area were much lower than to the left lens area, particularly with smaller-lensed glasses, due to gaps in protection between the face and the glasses. The results of this study reiterate the importance of employers providing eyewear based on the morphology of, and fit to, individual workers' faces.

Impact of latest generation cardiac interventional X-ray equipment on patient image quality and radiation dose for trans-catheter aortic valve implantations

OBJECTIVES

This study aimed to determine the impact on radiation dose and image quality of a new cardiac interventional X-ray system for trans-catheter aortic valve implantation (TAVI) patients compared to the previously-used cardiac X-ray system.

METHODS

Patient dose and image data were retrospectively collected from a Philips AlluraClarity (new) and Siemens Axion Artis (reference) X-ray system. Patient dose area product (DAP) and fluoroscopy duration of 41 patient cases from each X-ray system were compared using a Wilcoxon test. Ten patient aortograms from each X-ray system were scored by 32 observers on a continuous scale to assess the clinical image quality at the given phase of the TAVI procedure. Scores were dichotomised by acceptability and analysed using a Chi-squared test.

RESULTS

Significant reductions in patient dose (p << 0.001) were found for the new system with no significant change in fluoroscopy duration (p = 0.052); procedure DAP reduced by 55%, fluoroscopy DAP by 48% and "cine" acquisition DAP by 61%. There was no significant difference between image quality scores of the two X-ray systems (p = 0.06).

CONCLUSIONS

The new cardiac X-ray system demonstrated a very significant reduction in patient dose with no loss of clinical image quality. Advances in Knowledge: The huge growth of TAVI may impact on the radiation exposure of cardiac patients and particularly on operators including anaesthetists; cumulative exposure of interventional cardiologists performing high volume TAVI over 30-40 years may be harmful. The Phillips Clarity upgrade including improved image enhancement and optimised X-ray settings significantly reduced radiation without reducing clinically acceptable image quality.

[Effects on health of the Chernobyl accident: 30 years on]

This paper reflects the current state of research into the short- and long-term effects on health in the former Soviet Union and Europe of the nuclear accident in Chernobyl. It discusses the latest results of epidemiological studies and presents future research perspectives.

The Risk of Cataract among Survivors of Childhood and Adolescent Cancer: A Report from the Childhood Cancer Survivor Study

With therapeutic successes and improved survival after a cancer diagnosis in childhood, increasing numbers of cancer survivors are at risk of subsequent treatment-related morbidities, including cataracts. While it is well known that the lens of the eye is one of the most radiosensitive tissues in the human body, the risks associated with radiation doses less than 2 Gy are less understood, as are the long- and short-term cataract risks from exposure to ionizing radiation at a young age. In this study, we followed 13,902 five-year survivors of childhood cancer in the Childhood Cancer Survivor Study cohort an average of 21.4 years from the date of first cancer diagnosis. For patients receiving radiotherapy, lens dose (mean: 2.2 Gy; range: 0-66 Gy) was estimated based on radiotherapy records. We used unconditional multivariable logistic regression models to evaluate prevalence of self-reported cataract in relationship to cumulative radiation dose both at five years after the initial cancer diagnosis and at the end of follow-up. We modeled the radiation effect in terms of the excess odds ratio (EOR) per Gy. We also analyzed cataract incidence starting from five years after initial cancer diagnosis to the end of follow-up using Cox regression. A total of 483 (3.5%) cataract cases were identified, including 200 (1.4%) diagnosed during the first five years of follow-up. In a multivariable logistic regression model, cataract prevalence at the end of follow-up was positively associated with lens dose in a manner consistent with a linear dose-response relationship (EOR per Gy = 0.92; 95% CI: 0.65-1.20). The odds ratio for doses between 0.5 and 1.5 Gy was elevated significantly relative to doses <0.5 Gy (OR = 2.2; 95% CI: 1.3-3.7). The results from this study indicate a strong association between ocular exposure to ionizing radiation and long-term risk of pre-senile cataract. The risk of cataract increased with increasing exposure, beginning at lens doses as low as 0.5 Gy. Our findings are in agreement with a growing body of evidence of an elevated risk for lens opacities in populations exposed to doses of ionizing radiation below the previously suggested threshold level of 2 Gy.

Fitness costs of increased cataract frequency and cumulative radiation dose in natural mammalian populations from Chernobyl

A cataract is a clouding of the lens that reduces light transmission to the retina, and it decreases the visual acuity of the bearer. The prevalence of cataracts in natural populations of mammals, and their potential ecological significance, is poorly known. Cataracts have been reported to arise from high levels of oxidative stress and a major cause of oxidative stress is ionizing radiation. We investigated whether elevated frequencies of cataracts are found in eyes of bank voles Myodes glareolus collected from natural populations in areas with varying levels of background radiation in Chernobyl. We found high frequencies of cataracts in voles collected from different areas in Chernobyl. The frequency of cataracts was positively correlated with age, and in females also with the accumulated radiation dose. Furthermore, the number of offspring in female voles was negatively correlated with cataract severity. The results suggest that cataracts primarily develop as a function of ionizing background radiation, most likely as a plastic response to high levels of oxidative stress. It is therefore possible that the elevated levels of background radiation in Chernobyl affect the ecology and fitness of local mammals both directly through, for instance, reduced fertility and indirectly, through increased cataractogenesis.