High-dose UVA1 Research Articles

The Effect of UV-A / UV-B Radiation on Quality Changes of Harvested Curly Lettuce During the Storage

This study investigated the effects of UV-A and UV-B radiation on curly lettuce quality. Results focused on colour, total phenolic content, antioxidant activity, and ascorbic acid. The findings revealed that the highest phenolic content (46.1 mg GAE/100 g FL) had been observed in lettuce samples treated with high dose UV-B on the 7th day. The lowest phenolic content (13.7 mg GAE/100 g FL) was recorded in those treated with low dose UV-B on the same day of storage. Data showed an increase of 29.7% in antioxidant activity and 53.7% in total phenolic content after 7 days of storage in samples treated with high dose UV-B. High dose UV-A radiation was found to be the most effective in maintaining and enhancing the ascorbic acid content of the lettuce. UV applications did not cause yellowing in the stored lettuce leaves. Further research on different doses and optimization is recommended.

Oxygen-supplemented and topography-guided epithelium-on corneal crosslinking with pulsed irradiation for progressive keratoconus.

To investigate the effects of customized topography-guided epithelium-on crosslinking (epi-on CXL) with oxygen supplementation on procedural efficacy and corrected distance visual acuity (CDVA) in patients with progressive keratoconus (KC) at 1 year. Private eye clinic, Brisbane, Australia. Retrospective, single-center, nonrandomized case series. Topography-guided epi-on CXL using the Mosaic system was performed on patients with progressive KC. Oxygen goggles; transepithelial riboflavin; and pulsed, high UV-A irradiance (1 second on, 1 second off; 30 mW/cm2) were applied to enhance oxygen kinetics and bioavailabilities of riboflavin and UV-A. Guided by baseline topography, a higher UV-A dose (15 J/cm2) was applied to the area of steepest anterior curvature with decreasing fluence (as low as 7.2 J/cm2) toward the outer 9 mm. Postoperative CDVA and maximum keratometry (Kmax) were evaluated. 102 eyes (80 patients) were followed for 11.5 ± 4.8 months. At the latest follow-up, mean CDVA (logMAR), mean K, and Kmax (diopters [D]) improved from 0.18 ± 0.28, 46.2 ± 3.8, and 53.0 ± 5.67 at baseline to 0.07 ± 0.18, 45.8 ± 3.7, and 51.9 ± 5.56, respectively (P < .001). 3 eyes (3%) lost more than 1 CDVA line, and another 3 eyes (3%) had increased Kmax greater than 2 D. 43 eyes were followed for at least 12 months (n = 43): mean CDVA, mean K, and Kmax improved from 0.19 ± 0.33 logMAR, 46.5 ± 3.5 D, and 53.6 ± 5.67 D to 0.07 ± 0.17 logMAR, 46.0 ± 3.5 D, and 52.33 ± 5.49 D, respectively (P ≤ .002). No complications were observed. Tailoring oxygen-supplemented epi-on CXL with differential UV-A energy distributions, guided by baseline topography, in patients with KC seems to be safe and effective. At 1 year, study reports sustained improved CDVA and corneal stabilization.

Multiphoton FLIM Analyses of Native and UVA-Modified Synthetic Melanins.

To better understand the impact of solar light exposure on human skin, the chemical characterization of native melanins and their structural photo-modifications is of central interest. As the methods used today are invasive, we investigated the possibility of using multiphoton fluorescence lifetime (FLIM) imaging, along with phasor and bi-exponential fitting analyses, as a non-invasive alternative method for the chemical analysis of native and UVA-exposed melanins. We demonstrated that multiphoton FLIM allows the discrimination between native DHI, DHICA, Dopa eumelanins, pheomelanin, and mixed eu-/pheo-melanin polymers. We exposed melanin samples to high UVA doses to maximize their structural modifications. The UVA-induced oxidative, photo-degradation, and crosslinking changes were evidenced via an increase in fluorescence lifetimes along with a decrease in their relative contributions. Moreover, we introduced a new phasor parameter of a relative fraction of a UVA-modified species and provided evidence for its sensitivity in assessing the UVA effects. Globally, the fluorescence lifetime properties were modulated in a melanin-dependent and UVA dose-dependent manner, with the strongest modifications being observed for DHICA eumelanin and the weakest for pheomelanin. Multiphoton FLIM phasor and bi-exponential analyses hold promising perspectives for in vivo human skin mixed melanins characterization under UVA or other sunlight exposure conditions.

Role of Pel and Psl polysaccharides in the response of Pseudomonas aeruginosa to environmental challenges: oxidative stress agents (UVA, H2O2, sodium hypochlorite) and its competitor Staphylococcus aureus.

Pseudomonas aeruginosa is a versatile bacterium capable of adapting to a wide range of stress factors, including solar UVA radiation (400-315 nm). High UVA doses produce lethal effects due to the action of reactive oxygen species. Sublethal UVA doses also induces oxidative damage, but, in addition, it triggers a variety of adaptive responses, including the overexpression of pelA and pslA genes in P. aeruginosa. These genes encode the synthesis of Pel and Psl, which are essential polysaccharides in biofilm formation. The present study analysed the role of Pel and Psl in the adaptive responses generated by exposure to low UVA doses, and their importance in the response to lethal doses of UVA, hydrogen peroxide (H2O2), and sodium hypochlorite, in both planktonic cells and submerged and air-liquid interface (ALI) biofilms. It also studied the roles of Pel and Psl in P. aeruginosa-Staphylococcus aureus interaction. The results demonstrate that the capacity of sublethal UVA exposure to increase cell hydrophobicity and cell attachment and generate cross-protection phenomena in P. aeruginosa depends on the presence of Pel and Psl. The study also shows that Pel and Psl have a key role in the tolerance to lethal doses of UVA radiation, sodium hypochlorite and H2O2, in both biofilms and planktonic cells. Finally, co-culture assays showed total inhibition of S. aureus growth in presence of P. aeruginosa. This phenomenon depends, at least in part, on the simultaneous presence of Pel and Psl in planktonic cells and biofilms, suggesting a relevant role of these polysaccharides in the interaction between these species.

Effect of grape seed extract on skin fibroblasts exposed to UVA light and its photostability in sunscreen formulation.

Grape seed extract (GSE) is rich in polyphenolic compounds, particularly (+)-catechin (C) and (-)-epicatechin (EC). Strong antioxidant activity of these compounds makes GSE to be value-added to the cosmetics with anti-aging properties. However, a lack of stability in different environmental conditions makes GSE challenging for the development of photostable cosmetic sunscreen products. To evaluate photoprotective effects of GSE on human dermal fibroblasts irradiated with UVA light and assess photostability of catechins in cream formulations containing GSE alone or in combination with octyl methoxycinnamate (OMC). MTT assay was used to assess protective effects of GSE on fibroblasts irradiated with UVA light. A photostability of C and EC in GSE and in cream formulation containing GSE was investigated using high-performance liquid chromatography and confirmed by reflection and transmission spectrophotometry using Transpore™ tapes and polymethacrylate (PMMA) plates as substrates. High UVA doses damaged fibroblast structure and inhibited their growth. However, GSE increased cell viability and effectively protected them from UVA damage. Photostability of C and EC was achieved by combination of GSE and OMC that also improved absorption capacity of UV filter and increased overall efficacy of formulation. PMMA plates showed better applicability for in vitro photostability testing of sunscreen formulations. However, despite the instability of Transpore® tape under heat from UV exposure, it can still be economically a substrate of alternative choice for screening. GSE can be used as an effective and sustainable natural resource for prevention of UV-induced skin damage providing long-term protection against premature skin aging.

Effect of UVA1 on hypertrophic scarring in the rabbit ear model.

Hypertrophic scars (HTSs) are common and cause functional and psychological morbidity. UVA1 (340–400 nm) phototherapy has been previously shown to be effective in the treatment of localized scleroderma, systemic sclerosis, and POEMS syndrome with minimal side effects, all of which are presented as collagen fibrils hyperplasia that is common with scarring in skin histology. In the present study, we aimed to investigate the impact of UVA1 on the protein expression of TGF-β signal pathway and myofibroblasts in a rabbit model of cutaneous scarring. Full-thickness skin wounds (2 cm × 5 cm in diameter) were made in New Zealand white rabbits to establish the hypertrophic scarring model. New Zealand white rabbits were divided into two treatment groups (n=30 wounds per group with an equal number of controls): medium-dose of UVA1 phototherapy group: 60 J/cm2; high-dose of UVA1 phototherapy group: 110 J/cm2. Left ears were used for treatment and the right ones were used for control. Treatment was administered five times weekly for 6 weeks. Treated and untreated control wounds were harvested at various time points and examined by histologic examination, immunohistochemical assessment, and ultrastructural evaluation. The results showed that UVA1 phototherapy caused a significant reduction in dermal thickness by histological features, whereas the scar index was descended significantly in both medium- and high-dose UVA1 groups compared with the control group. Examination of immunohistochemistry also revealed a marked suppression of tissue growth factor-β (TGF-β) (both medium- and high-dose), α smooth muscle actin (α-SMA) (only high-dose), and tissue inhibitor of metalloproteinase 1 (TIMP-1) (only high-dose), and apparent increase in matrix metalloproteinases (MMP-1) (both medium- and high-dose) compared with the control. The ultrastructural evaluation showed the collagen fibers’ diameter had shrunk, and that fibroblastic cytoplasm was not affluent and in a quiescent stage. These findings of the present study suggested that administration of UVA1 irradiation is effective to improve the experimental HTS model and raises a possibility of the therapeutic approach of UVA1 in the scar. Although not directly examined in the present study, MMP inhibition is hypothesized to be responsible for this effect. However, early UVA1 treatment could not prevent the formation of scar model.

The study of induction of 8-methoxypsoralen (8-MOP) SOS-response in bacteria Escherichia coli

8-Methoxypsoralen (8-MOP) is used for photochemotherapy of psoriasis and vitiligo. In therapy, called PUVA therapy, the affected skin of a patient who has previously been prescribed 8-MOP is irradiated with UV-A (> 320 nm). As a result of the photochemical reaction, 8-MOP forms a covalent bond with the pyrimidine bases of DNA and forms both monofunctional and bifunctional adducts. The latter cause 8-MOP-mediated cytotoxicity, leading to the death of psoriatic cells. However, in surviving cells, these same adducts can cause 8-MOP genotoxicity. For a comparative study of the cytotoxicity and genotoxicity of 8-MOP, the E. coli MG1655 lux biosensor (pColD-lux), carrying a recombinant plasmid with a lux operon controlled by the colD gene promoter, was first used. The colD gene (cda) is part of the E. coli SOS-regulon, which provides DNA repair and cell resistance to DNA damage. The death of bacteria was taken into account as an indicator of the cytotoxicity of 8-MOP+UV-A, and the death of bacteria was taken into account by the change in the luminescence intensity of the biosensor. Induction of 8-MOP-mediated SOS-response in bacteria depends on the dose of UV-A, and on the concentration of 8-MOP. At high UV-A doses, a 25-fold decrease in the survival of bacterial cells was detected (from 2 × 108 to 8 × 106 CFU), and in viable cells, an increase in the intensity of the SOS response by 675 times in terms of 106 cells. Thus, it was shown that in the bacterial test system, the genotoxic effect of 8-MOP is several times higher than its cytotoxicity. Key words: 8-methoxypsoralen, lux biosensor, E. coli, colD gene promoter, SOS response, UV radiation, adducts.

Impact of TiO2/UVA photocatalysis on THM formation potential

In drinking water treatment plants, reduction of trihalomethane formation potential (THMFP) can be reached through precursor removal prior chlorine disinfection. In this work, the impact of TiO2/UVA photocatalytic process on THMFP has been studied using different phenolics (phenol, resorcinol, catechol, hydroquinone and gallic acid) and citric acid as NOM surrogates. A solution of each surrogate was photocatalytically treated at pH 7 applying different UVA doses and then chlorinated. Resorcinol oxidation by TiO2/UVA and THMFP reduction go hand in hand, indicating that the intermediates hardly form THMs when chlorinated. For the rest of surrogates, intermediates with medium-high specific THMFP (maximum values 40–120 μg CHCl3 (mg DOC)−1 for phenols; and ∼1000 μg CHCl3 (mg DOC)−1 for citric acid) are initially formed and disappear at higher UVA doses. TiO2/UVA treatment of water matrices with high and low specific UV absorption at 254 nm (SUVA254) (Sigma-Aldrich humic acid, pH 7; and water from Villar del Rey reservoir; Badajoz-Spain), was also investigated. For surface water UVA doses higher than 5 kWh m−3 were needed to achieve a THMFP below 100 μg THM L−1. During water treatment, an initial negative impact of AOPs in general and TiO2/UVA in particular on THMFP is expected.

HEA-PVA gel system for UVA radiation dose measurement

Acrylic monomer is known to be sensitive to ultraviolet radiation (UVR) through photoinitiator. Upon irradiation, the acrylic monomers formed stable polymer through free radical polymerization, hence its appearance will change from colorless and transparent to colored and non-transparent. Furthermore, the degree of changes was based on the UVR dose, and those optical changes could be detected by UV–vis spectrophotometer at the fixed wavelength of 550nm. In this study, we used 2-hydroxyethyl acrylate (HEA) as acrylic monomer, which mixed with polyvinyl alcohol (PVA), and finally obtained a three-dimensional hydrogel material through cross-linking by glutaraldehyde (GA). After doping with photoinitiator-Bis(2,6-difluoro-3-(1-hydropyrro-1-yl)-phenyl) titanocene (784), the gel material was sensitive to UV-A radiation (400–315nm), which forms an important part (~97%) of the natural solar UV radiation reaching the earth surface. The behavior of different formulations' dose response sensitivity, detector linearity, diffusion, stability after UVA radiation were investigated. The results showed that when the dosage range of UVA radiation was 0–560J/cm2, the gel had a great sensitivity and the linearity was found to be closed to 1. After UVA radiation, the gel also had a very good optical stability. In addition to this, when irradiated with high dose UVA, the gel could maintain a low diffusion.

Exposure to low UVA doses increases KatA and KatB catalase activities, and confers cross-protection against subsequent oxidative injuries in Pseudomonas aeruginosa.

Solar UVA radiation is one of the main environmental stress factors for Pseudomonas aeruginosa. Exposure to high UVA doses produces lethal effects by the action of the reactive oxygen species (ROS) it generates. P. aeruginosa has several enzymes, including KatA and KatB catalases, which provide detoxification of ROS. We have previously demonstrated that KatA is essential in defending P. aeruginosa against high UVA doses. In order to analyse the mechanisms involved in the adaptation of this micro-organism to UVA, we investigated the effect of exposure to low UVA doses on KatA and KatB activities, and the physiological consequences. Exposure to UVA induced total catalase activity; assays with non-denaturing polyacrylamide gels showed that both KatA and KatB activities were increased by radiation. This regulation occurred at the transcriptional level and depended, at least partly, on the increase in H2O2 levels. We demonstrated that exposure to low UVA produced a protective effect against subsequent lethal doses of UVA, sodium hypochlorite and H2O2. Protection against lethal UVA depends on katA, whilst protection against sodium hypochlorite depends on katB, demonstrating that different mechanisms are involved in the defence against these oxidative agents, although both genes can be involved in the global cellular response. Conversely, protection against lethal doses of H2O2 could depend on induction of both genes and/or (an)other defensive factor(s). A better understanding of the adaptive response of P. aeruginosa to UVA is relevant from an ecological standpoint and for improving disinfection strategies that employ UVA or solar irradiation.

Contribution of UVA irradiance to the erythema and photoaging effects in solar and sunbed exposures

Even though UVA irradiance had not been considered detrimental to human skin for years, nowadays it is recognized for its role in photoaging and other biological responses. The ratio UVA/UVB is about 17 at a solar zenith angle (SZA) of 20° and it is almost constant up to 60° when it rapidly increases since the UVB wavelengths (280–320nm) are more attenuated than the UVA waveband (320–400nm). For a constant SZA, the ratio increases with the ozone content. The UVA component of the solar erythemal irradiance ranges from 20% at 20° to 30% at 60°, whereas it varies from 50% to 80% in the two different types of measured sunbeds. Moreover, the different spectral distribution of the lamps used for artificial tanning leads frequently to high UVA doses. The biological responses related to skin photoaging (skin sagging and elastosis) could be around fourfold the equivalent solar irradiance at midday in summer midlatitudes and they can be important in unprotected UVA exposures to sunbeds. The UVA dose accumulated during the time required in reaching 1 minimum erythemal dose (MED) increases with the SZA since the exposure durations are longer. Indeed, seasonal differences in the mean UVA dose are observed due to variations in the ozone content that results in longer exposure times without erythema. Although an artificial tanning session is usually shorter than one hour, the UVA dose from sunbeds during the time for 1 MED for skin type II (250Jm−2) can be 2–4 times larger than the solar dose, depending on the lamp spectral emission.

Photo(chemo)therapy in the management of atopic dermatitis: an updated systematic review with implications for practice and research

Photo(chemo)therapy is a common treatment modality in patients with atopic dermatitis (AD), but evidence on its effectiveness has not been recently systematically reviewed. To evaluate the effect of treatment with photo(chemo)therapy in patients with AD and to make treatment recommendations on basis of the evidence. We performed an electronic literature search in MEDLINE (OVID), EMBASE (OVID), the Cochrane Central Register of Controlled Trials (CENTRAL), Global Resource of EczemA Trials (GREAT) and prospective trial registers, complemented with a search of PubMed to find recent studies not yet available in OVID MEDLINE. All randomized controlled trials (RCTs) on phototherapy for the treatment of AD were considered for data extraction. Nineteen studies were included (905 participants). The identified RCTs were generally clinically and qualitatively heterogeneous. Therefore a formal meta-analysis was not feasible. Conclusions must be drawn carefully because of small sample sizes, varying study quality and sometimes the absence of direct comparisons, but on the basis of the included evidence, ultraviolet (UV) A1 and narrowband (NB)-UVB appeared the most effective treatment modalities for the reduction of clinical signs and symptoms. No difference between high-dose UVA1 and medium-dose UVA1 was seen. UVAB was shown to be more effective than UVA and broadband-UVB for the improvement of clinical symptoms, but not compared with UVA1. Other effective treatment options include full-spectrum light, psoralen plus UVA and balneophototherapy. No serious side-effects were reported. Phototherapy can be a valid therapeutic option for patients with AD. Based on the results of this review, preference is given to UVA1 and NB-UVB. Further well-designed, adequately powered RCTs are required.

Acrylic nail curing UV lamps: High-intensity exposure warrants further research of skin cancer risk

Acrylic nail curing UV lamps: High-intensity exposure warrants further research of skin cancer risk

Ultraviolet A1 Phototherapy of Mycosis Fungoides

Ultraviolet A1 Phototherapy of Mycosis Fungoides

Epidemiological evidence that UVA radiation is involved in the genesis of cutaneous melanoma

Epidemiological data have contributed to the classification in 2009 of the full ultraviolet (UV) radiation spectrum as carcinogenic to humans. We reviewed the epidemiological evidence that UVA could be involved in the genesis of cutaneous melanoma. Use of artificial UV tanning devices (sunbeds) consists mainly of repeated exposure to high UVA doses. Epidemiological studies published over the last years confirmed the association between sunbed use and melanoma. Sunbed use is the most probable cause of an epidemic of melanoma that took place in Iceland from 1990 to 2006. The four-fold increase in melanoma incidence was not followed by an increase in melanoma mortality. Sunscreens were primarily devised for the prevention of sunburn, and UVB is the wavelength causing most sunburns. All observational studies and randomized trials show that sunscreen use may extend sun exposure intended for getting a tan, while it does not necessarily decrease sunburn occurrence. Sunscreen use for tan acquisition would thus lead to similar exposure to UVB and greater exposure to UVA, which could explain the slightly higher melanoma risk often found among sunscreen users. UVA could be involved in the occurrence of nonlife-threatening melanoma. The increasing use of sunbeds and of sunscreens may partly explain why melanoma incidence increases in most light-skinned populations without concomitant increase in mortality.

Pompholyx

Pompholyx is a vesicobullous disorder of the palms and soles. The condition is hard to treat because of the peculiarities of the affected skin, namely the thick horny layer and richness of the sweat glands. In this article, we review the available therapies, and score the treatments according to the level of evidence. The cornerstones of topical therapy are corticosteroids, although calcineurin inhibitors also seem to be effective. Topical photochemotherapy with methoxsalen (8-methoxypsoralen) is as effective as systemic photochemotherapy or high-dose UVA-1 irradiation. Systemic therapy is often necessary in bullous pompholyx. Corticosteroids are commonly used although no controlled study has been published to date. For recalcitrant cases, corticosteroids are combined with immunosuppressants. Alitretinoin has efficacy in chronic hand dermatitis including pompholyx. Another evolving treatment seems to be the intradermal injection of botulinum toxin. Radiotherapy might be an option for selected patients not responding to conventional treatment. In practice, patients benefit most from a combination of treatments.

Merkel cell carcinoma arising in immunosuppressed patients treated with high-dose ultraviolet A1 (320-400 nm) phototherapy: a report of two cases

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine tumour of the skin. Though immunodeficiency is the most relevant risk factor, ultraviolet (UV) radiation is also involved, but as of yet we do not know the action spectrum, pattern or dose which would produce a dangerous exposure. A retrospective study of two immunosuppressed patients who developed MCC during, or soon after a treatment cycle with high dose UVA1 exposures was conducted, in order to understand wether repeated exposures to suberythemogenic UVA1 radiation may have a cancerogenic activity provoking MCC in immunosuppressed patients.

The Alternative Complement Pathway Seems to be a UVA Sensor that Leads to Systemic Immunosuppression

UV wavebands in sunlight are immunomodulatory. About half the amount of UVA within a minimum erythemal dose of sunlight is systemically immunosuppressive, whereas higher doses protect from UVB immunosuppression in mice. We have earlier shown that these responses to UVA are genetically restricted, as they occur in C57BL/6 but not in Balb/c mice. We used gene set enrichment analysis of microarray data and real-time reverse transcriptase (RT)-PCR confirmation to determine the molecular mechanisms associated with UVA immunomodulation. We found upregulation of mRNA for the alternative complement pathway. The core-enriched genes complement component 3, properdin, and complement factor B were all activated by the immunosuppressive dose of UVA only in UVA-responsive C57BL/6 but not in unresponsive BALB/c mice. This therefore matched the genetic restriction and dose responsiveness of UVA immunosuppression. The immune-protective higher UVA dose prevented UVB from downregulating chemokine receptor 7 and IL-12B, and decreased IL-10, supporting the earlier identification of IL-12 and IL-10 in high-dose UVA protection from UVB immunosuppression. Our study has identified activation of the alternative complement pathway as a trigger of UVA-induced systemic immunosuppression and suggests that this pathway is likely to be an important sensor of UVA-induced damage to the skin.

Pompholyx or dyshidrosis

Pompholyx is an inflammatory vesicobullous disorder of the palms and soles. Although originally thought to be related to eccrine gland pathology, the condition is now considered to be part of the eczema spectrum. Pompholyx has a number of differential diagnoses and the etiopathology of this disease is not uniform. It can develop on the basis of atopy, contact irritation and contact sensitization, mycid reaction and as a side effect of drug treatment. Pompholyx treatment is challenging: topical therapy is based on corticosteroids and calcineurin inhibitors. Topical and systemic photochemotherapy and high-dose UVA-1 irradiation have been successfully used. Systemic therapy is often necessary in advanced cases of pompholyx. Corticosteroids are commonly used, sometimes combined with immunosuppressants. Alitretinoin has efficacy in chronic hand eczema including pompholyx. Another evolving treatment seems to be the intradermal injection of botulinum toxin. In practice, patients benefit most from a combination o...

Effect of Two Different UVA Doses on the Rabbit Cornea and Lens

The aim of the present paper was to examine the irradiation effect of two doses of UVA rays (365 nm) on the rabbit cornea and lens. Corneas of anesthetized adult albino rabbits were irradiated with UVA rays for 5 days (daily dose 1.01 J cm(-2) in one group of rabbits and daily dose 2.02 J cm(-2) in the second group of animals). The third day after the last irradiation, the rabbits were killed, and their eyes were employed for spectrophotometrical, biochemical and immunohistochemical investigations. Normal eyes served as controls. Absorption spectra of the whole corneal centers were recorded over the UV-VIS (visible) spectral range. Levels of antioxidant and prooxidant enzymes, nitric oxide synthases and nitric oxide (indirectly measured as nitrate concentration) were investigated in the cornea. Malondialdehyde, a byproduct of lipid peroxidation, was examined in the cornea and lens. The results show that the staining for endothelial nitric oxide synthase was more pronounced in corneas irradiated with the higher UVA dose. Otherwise, UVA rays at either dose did not significantly change corneal light absorption properties and did not cause statistically significant metabolic changes in the cornea or lens. In conclusion, UVA rays at the employed doses did not evoke harmful effects in the cornea or lens.