Add time:08/17/2019         Source:sciencedirect.com

Blocking a selected wavelength range from the light spectrum can have multiple benefits. Ultra-violet (UV) radiation is detrimental to the retina, necessitating its blocking through sunglasses and contact lenses. The near-visible light also has enough energy to cause damage but, is typically not blocked by commercial lenses. Filtering light can also be useful to patients with migraines, amblyopia, and color blindness. Here, to achieve blocking, incorporation of pigments extracted from colored agro-products into contact lenses is explored. Pigment extraction from food powders including turmeric, spinach, paprika, and woad powders in ethanol is demonstrated. Lens immersion in pigment concentrated ethanol is done to facilitate swelling, allowing rapid pigment uptake. Pigment incorporation ensures the absence of visible light scattering, lens opacity, and leaching. The characterization of pigmented lenses is done through absorptivity and transmittance measurements. Degradation measurements investigate the stability of the green pigment extract from spinach powder with time. p-HEMA and silicone hydrogels loaded with >400 µg/g turmeric pigment act as class 1 UV blockers retaining >90% visible light transparency and screening >95% of the UVR spectra. Spinach, paprika, and woad powder loaded silicone lenses mitigate >20% visible light transmission from selective wavelengths finding applications in photophobia, amblyopia treatment, and color vision deficiency management.

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