Tsutomu Okuno

Evaluation of Blue-Light Hazards from Various Light Sources

Visible light of short wavelength (blue light) may cause a photochemical injury to the retina, called photoretinitis or blue-light hazard. In this study, various light sources were evaluated for blue-light hazard. These sources include the sun, the arc associated with arc welding and plasma cutting, molten steel, iron and glass, the interior of furnaces, the arc or envelope of discharge lamps, the filament or envelope of incandescent lamps, the envelope of fluorescent lamps and light-emitting diodes. The spectral radiance of each light source was measured, and blue-light effective radiance and the corresponding permissible exposure time per day were calculated in accordance with the ACGIH (American Conference of Governmental Industrial Hygienists) standard. The sun, arc welding, plasma cutting and the arc of discharge lamps were found to have extremely high effective radiances with corresponding permissible exposure times of only 0.6-40 s, suggesting that viewing these light sources is very hazardous to the retina. Other light sources were found to have low effective radiances under the study conditions and would pose no hazard, at least for short exposure times.

Transmission spectrums and retinal blue-light irradiance values of untinted and yellow-tinted intraocular lenses

PURPOSE: To record and compare the spectral transmission characteristics of foldable untinted and yellow‐tinted intraocular lenses (IOLs) and evaluate the protective effects against retinal damage by sunlight. SETTING: Shimane University Faculty of Medicine, Izumo, Japan. METHODS: The study evaluated 3 untinted IOLs (SA60AT, VA‐60BBR, AU6 K) and 3 yellow‐tinted IOLs (SN60AT, YA‐60BBR, AU6 N) of 3 lens powers (+10.0 diopters [D], +20.0 D, and +30.0 D). Spectral transmittance in the wavelength range of 300 to 800 nm was measured using a spectrophotometer through 2.5 mm and 4.5 mm diameter apertures. Retinal hazard indices, including blue‐light irradiance and maximum permissible exposure duration per day (tmax) for viewing sunlight, were calculated. RESULTS: The untinted IOLs completely absorbed ultraviolet (UV) light and nearly completely absorbed transmitted visible light at wavelengths longer than 440 nm. Yellow‐tinted IOLs absorbed more in the blue‐light range (400 to 500 nm) than untinted IOLs. The blue‐light irradiance was 34.2% to 56.0% lower with the SN60AT IOL than with the SA60AT IOL, 35.2% to 48.4% lower with the YA‐60BBR IOL than with the VA‐60BBR IOL, and 16.8% to 22.9% lower with the AU6 N IOL than with the AU6 K IOL. Blue‐light irradiance values of SN60AT and YA‐60BBR IOLs decreased as the lens power increased. CONCLUSIONS: Compared with aphakic eyes, UV‐blocking untinted IOLs reduced the blue‐light irradiance value by 60%; yellow‐tinted IOLs conferred an additional 17% to 56% reduction. The difference in lens power was significantly related to the blue‐light irradiance value of some yellow‐tinted IOLs. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Occupational exposure levels of static magnetic field during routine MRI examination in 3 T MR system

Occupational exposure to the high static magnetic fields (SMFs) during magnetic resonance imaging (MRI) examinations raises concerns of adverse health effects. In this study, personal exposure monitoring of the magnetic fields during routine examinations in two 3 T MRI systems was carried out. A three-axis Hall magnetometer was attached to a subjects chest during monitoring. Data acquisition started every time the subject entered the scanner room and ended when the subject exited the room. Four radiologic technologists from two different institutes participated in this study. The maximum exposed field ranged from 0 to 1250 mT and the average peak magnetic field (B) was 428 ± 231 mT (mean ± standard deviation (SD): number of samples (N) = 103). Then, the relationship between exposure levels and work duties was analyzed. The MRI examination of the head or neck showed the highest average peak B among four work categories. These results provide information of real exposure levels for 3 T MRI system operators and can also improve the current practical training advice for preventing extra occupational field exposure.

Environmental temperature and cataract progression in experimental rat cataract models.

PURPOSE To clarify whether or not ambient temperature relates to cataract development or the progression of cataract formation. MATERIALS AND METHODS 36 Brown Norway rats were divided into two groups, a high-temperature (35 +/- 2 degrees C, H = high) breeding group and a regular-temperature (24 +/- 2 degrees C, L = low) group. Each group was further divided into an experimentally induced diabetic cataract subgroup (50 mg/kg streptozotocin, DM), an ultraviolet B exposure-induced cataract subgroup (200 mJ/cm2, UV), and a normal control subgroup (C = control). Slit-lamp microscopy and an anterior image analysis system (EAS-1000) were used to evaluate lens changes. RESULTS Both the HC and HUV groups in the 35 degrees C conditions showed higher light scattering than that of the 24 degrees C conditions (LC and LUV) 3 weeks after the start of the experiment. Nine weeks after the start of the experiment, all the rats of the UV subgroups (HUV and LUV) developed anterior subcapsular cataract. The temperature did not have much influence on the progression of the UV-B-induced cataract. From 18 days after the start of the experiment, the HC subgroup showed a wider light scattering area than the LC. An increase in abnormal nuclear scattering light in the crystalline lens of group HC was found in 9 weeks after the start of the experiment, and at the end of the experiment (78 weeks later), dense abnormal nuclear light scattering was found including the prenuclear area. In contrast, the HDM group in the 35 degrees C conditions showed slower cataract progression than that of the LDM group at 24 degrees C room temperature. CONCLUSIONS Although further experiments are necessary before we can draw any conclusions about temperature and nuclear changes, paying attention to the effects of temperature on the lens is worthwhile.

Blue-Light Hazard from CO2 Arc Welding of Mild Steel

OBJECTIVES The objective was to quantify the blue-light hazard from CO(2) arc welding of mild steel. METHODS The spectral radiance of arcs in CO(2) arc welding of mild steel was measured for solid and flux-cored wires at welding currents of 120-480 A. Effective blue-light radiance and the maximum acceptable exposure duration were calculated from the spectral radiance using their definitions in American Conference of Governmental Industrial Hygienists guidelines. RESULTS The effective blue-light radiance ranged from 22.9 to 213.1 Wcm(-2)sr(-1). The corresponding maximum acceptable exposure duration was only 0.47-4.36 s, meaning that the total daily exposure to the welding arc without eye protection should not exceed this duration. CONCLUSIONS It is very hazardous to view the arcs in CO(2) arc welding of mild steel. Welders and their helpers should use appropriate eye protectors in these arc-welding operations. Also, they should avoid direct light exposure when starting an arc-welding operation.

Effects of UV wavelength on cell damages caused by UV irradiation in PC12 cells

Ultraviolet (UV) radiations present in sunlight are a major etiologic factor for many skin diseases and induce DNA damage through formation of cyclobutane pyrimidine dimer (CPD). This study was conducted to determine the toxicological effects of different wavelengths (250, 270, 290, and 310 nm) and doses of UV radiation on cell viability, DNA structure, and DNA damage repair mechanisms in a PC12 cell system. For this, we evaluated cell viability and CPD formation. Cell survival rate was markedly decreased 24h after UV irradiation in a dose-dependent manner at all wavelengths (except at 310 nm). Cell viability increased with increasing wavelength in the following order: 250<270<290<310 nm. UV radiation at 250 nm showed the highest cell killing ability, with a median lethal dose (LD50) of 120 mJ/cm(2). The LD50 gradually increased with increase in wavelength. Among the 4 wavelengths tested, the highest LD50 (6000 mJ/cm(2)) was obtained for 310 nm. CPD formation decreased substantially with increasing wavelength. Among the 4 wavelengths, the proportion of CPD formation was highest at 250 nm and lowest at 310 nm. On the basis of LD50 values for each wavelength, PC12 cells irradiated with UV radiation of 290 nm showed maximum DNA repair ability, whereas those irradiated with the 310-nm radiation did not show any repair ability. Toxicity of UV radiation varied with wavelengths and exposure doses.

Hazards of solar blue light

Short-wavelength visible light (blue light) of the Sun has caused retinal damage in people who have stared fixedly at the Sun without adequate protection. The author quantified the blue-light hazard of the Sun according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines by measuring the spectral radiance of the Sun. The results showed that the exposure limit for blue light can be easily exceeded when people view the Sun and that the solar blue-light hazard generally increases with solar elevation, which is in accordance with a model of the atmospheric extinction of sunlight. Viewing the Sun can be very hazardous and therefore should be avoided except at very low solar elevations.

Temperature rises in the crystalline lens from focal irradiation

Many types of ophthalmic instruments produce a concentrated focal irradiance in the lens. Instruments that illuminate large areas of the retina—known as “Maxwellian-view,” are but one example, and there are concerns about the potential hazards associated with this optical system. The transfer of the heat generated in the human eye in Maxwellian-view illumination or similar focal-beam situations was simulated using a mathematical model to determine the temperature elevations induced in the human eye. The maximum temperature rise in the lens region was examined to quantitatively assess the potential thermal hazard to the lens. It was shown that Maxwellian-view illumination or similar focal-beam situations can cause thermal injury to the lens under certain conditions, and that this hazard is greater for incident wavelengths of about 320–420 nm than for longer wavelengths. The risk of thermal injury increases as exposure duration increases, and the risk tends to increase as the beam waist diameter or Maxwellian-view angle decreases.

Ultraviolet Action Spectrum for Cell Killing of Primary Porcine Lens Epithelial Cells

Ultraviolet Action Spectrum for Cell Killing of Primary Porcine Lens Epithelial Cells: Tsutomu OKUNO, et al. Human Engineering and Risk Management Research Group, National Institute of Occupational Safety and Health, Japan—

4-Hydroxyhexenal- and 4-Hydroxynonenal-Modified Proteins in Pterygia

Oxidative stress has been suspected of contributing to the pathogenesis of pterygia. We evaluated the immunohistochemical localization of the markers of oxidative stress, that is, the proteins modified by 4-hydroxyhexenal (4-HHE) and 4-hydroxynonenal (4-HNE), which are reactive aldehydes derived from nonenzymatic oxidation of n-3 and n-6 polyunsaturated fatty acids, respectively. In the pterygial head, labeling of 4-HHE- and 4-HNE-modified proteins was prominent in the nuclei and cytosol of the epithelium. In the pterygial body, strong labeling was observed in the nuclei and cytosol of the epithelium and proliferating subepithelial connective tissue. In normal conjunctival specimens, only trace immunoreactivity of both proteins was observed in the epithelial and stromal layers. Exposures of ultraviolet (330 nm, 48.32 ± 0.55 J/cm2) or blue light (400 nm, 293.0 ± 2.0 J/cm2) to rat eyes enhanced labeling of 4-HHE- and 4-HNE-modified proteins in the nuclei of conjunctival epithelium. Protein modifications by biologically active aldehydes are a molecular event involved in the development of pterygia.