A novel sensor array for field based ocular ultraviolet radiation measurements

A numerical model for quantifying exposure to natural and artificial light in human health research

Various skin and ocular pathologies can result from overexposure to ultraviolet radiation and blue light. Assessing the potential harm of exposure to these light sources requires quantifying the energy received to specific target tissue. Despite a well-established understanding of the light-disease relationship, the quantification of received energy in diverse lighting scenarios proves challenging due to the multitude of light sources and continuous variation in the orientation of receiving tissues (skin and eyes). This complexity makes the determination of health hazards associated with specific lighting conditions difficult. In this study, we present a solution to this challenge using a numerical approach. Through the implementation of algorithms applied to 3D geometries, we created and validated a numerical model that simulates skin and ocular exposure to both natural and artificial light sources. The resulting numerical model is a computational framework in which customizable exposure scenarios can be implemented. The ability to adapt simulations to different configurations for study makes this model a potential investigative method in human health research.

Assessing Human Eye Exposure to UV Light: A Narrative Review

Exposure to ultraviolet light is associated with several ocular pathologies. Understanding exposure levels and factors is therefore important from a medical and prevention perspective. A review of the current literature on ocular exposure to ultraviolet light is conducted in this study. It has been shown that ambient irradiance is not a good indicator of effective exposure and current tools for estimating dermal exposure have limitations for the ocular region. To address this, three methods have been developed: the use of anthropomorphic manikins, measurements through wearable sensors and numerical simulations. The specific objective, limitations, and results obtained for the three different methods are discussed.

Efficiency of ocular UV protection by clear lenses

Ocular UV doses accumulate all-day, not only during periods of direct sun exposure. The UV protection efficiency of three clear lenses was evaluated experimentally, validated by simulation, and compared to non-UV protection: a first spectacle lens with a tailored UV absorber, a second spectacle lens, minimizing UV back reflections, as well as a third spectacle lens, combining both. A tailored UV-absorber efficiently reduced overall UV irradiance to 7 %, whereas reduction of back-reflections still left UV irradiance at 42 %. Thus, clear lenses with a tailored UV absorber efficiently protect the eye from UV, supplementing sun glasses wear to an all-day protection scenario.

Distributions of Direct, Reflected, and Diffuse Irradiance for Ocular UV Exposure at Different Solar Elevation Angles

To analyze intensities of ocular exposure to direct (E_o,dir), reflected (E_o,refl), and diffuse (E_o,diff) ultraviolet (UV) irradiance at different solar elevation angles (SEAs), a rotating manikin and dual-detector spectrometer were used to monitor the intensity of ocular exposure to UV irradiation (E_o) and ambient UV radiation (UVR) under clear skies in Sanya, China. E_o,dir was derived as the difference between maximum and minimum measured E_o values. E_o,refl was converted from the value measured at a height of 160 cm. E_o,diff was calculated as the minimum measured E_o value minus E_o,refl. Regression curves were fitted to determine distributions of intensities and growth rates at different wavelengths and SEAs. E_o,dir differed from ambient UVR exposure. Linear, quadratic, and linear E_o,dir distributions were obtained in SEA ranges of 14°–30°, 30°–50°, and 50°–90°, respectively, with maximum E_o,dir at 32°–38° SEA. Growth rates of E_o,dir with increasing wavelength were fitted with quadratic functions in all SEA ranges. Distributions and growth rate of E_o,refl values were fitted with quadratic functions. Maximum E_o,diff was achieved at the same SEA for all fitted quadratic functions. Growth rate of E_o,diff with increasing wavelength was fitted with a linear function. E_o,dir distributions were fitted with linear or quadratic functions in different SEA ranges. All E_o,refl and E_o,diff distributions were fitted with quadratic functions. As SEA increased, the E_o,dir portion of E_o increased and then decreased; the E_o,refl portion increased from an initial minimum; and the E_o,diff portion first decreased and then increased. The findings may provide data supporting on construction of a mathematical model of ocular UV exposure.

A quantitative assessment of the burden and distribution of Lisch nodules in adults with neurofibromatosis type 1

PURPOSE

The presence of two or more Lisch nodules (melanocytic hamartomas of the iris) is one of seven diagnostic criteria for neurofibromatosis type 1 (NF1), a common monogenic disorder of dysregulated neurocutaneous growth. The hypothesis that Lisch nodules arise secondary to exposure to ultraviolet (UV) radiation from sunlight was investigated.

METHODS

Lisch nodule burden was mapped and quantified in the irides of 77 adults with NF1. Lifetime sunlight (UV radiation) exposure was inventoried, NF1 neurocutaneous severity determined, and two NF1 mutations predictive of severity selectively genotyped.

RESULTS

There was high interindividual variability in Lisch nodule burden. Lisch nodules were primarily located in the inferior hemifield (half) of the iris, regardless of its color (P = 3.0 x 10(-20)). Light irides harbored significantly more Lisch nodules than dark irides (P = 4.8 x 10(-5)). There was no statistically significant correlation of Lisch nodule burden to lifetime sunlight exposure "dose" or NF1 neurocutaneous severity.

CONCLUSIONS

The difference in Lisch nodule burden between the superior and inferior iris hemifields is most likely due to the sunlight-shielding effects on the superior half by periocular structures. The difference in Lisch nodule burden between light and dark irides is probably due to the photoprotective effects of pigmentation. The genes underlying the control of iris color may thus be viewed as modifiers of severity of Lisch nodule burden in NF1. Given the role of UV radiation and, presumably, DNA damage in Lisch nodule pathogenesis, "benign tumor of the iris," not "hamartoma," may be a better descriptor.

Novel Method for Determining Hydrogel and Silicone Hydrogel Contact Lens Transmission Curves and Their Spatially Specific Ultraviolet Radiation Protection Factors

PURPOSE

Anterior ocular tissues exposed to high levels of toxic ultraviolet (UV) radiation may undergo physiologic changes leading to diseases that can alter the ocular surface, particularly in the stem cell-rich limbal region. UV radiation-blocking hydrogel contact lenses provide protection across the ocular surface, which varies according to the lens thickness.

METHODS

A novel fiber optic spectrophotometer front-end system has been developed to measure lens transmission curves at test points across lens surfaces to determine optical properties based on the Beer-Lambert law. Factors determining the transmission curves include the hydrogel lens used, its refractive index, whether a UV radiation-blocking dopant is incorporated, the water content, and the thickness of the lens. Test lenses of equal power were placed over a detecting fiber optic and illuminated by a deuterium source, and transmission spectra were recorded. The small optical sampling size allowed the spectral transmission profile to be determined across the lens surface, and comparisons were made with different lenses.

RESULTS

Transmission curves across the lenses showed greater UV radiation-blocking capacity at the thicker peripheral region, with the 50% cutoff wavelength moving toward the visible spectrum by 10 nm from the center to the periphery. In addition, the ability to determine the spatially specific absorption coefficient and the related UV radiation protection factor was demonstrated.

CONCLUSIONS

The system measures spatial variation in lens transmission and comparing different lens types while overcoming many of the handling limitations of cuvette-based spectrophotometer methods. The data show good agreement with published transmission curves and allow intralens and interlens comparisons.