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    Evidence weak for blue light-filtering IOLs

    Only weak evidence supports the use of IOLs that filter visible blue light, researchers say.

    “On the basis of currently available evidence, one cannot advocate for the use of blue-light-filtering IOLs over UV-only filtering IOLs,” wroite X. Li, Waterford Institute of Technology, Waterford, Ireland, and colleagues.

    They published their review of the research on the lenses in the journal Eye.

    Manufacturers and distributers have been claiming benefits for IOLs that filter visible short-wavelength light.

    Blue light is scattered more than light of longer wavelengths, Li and colleagues wrote, and blue light scatter is the predominant cause of veiling luminance and glare disability.

    In a healthy eye, lutein, zeaxanthin, and mesozeaxanthin—collectively referred to as macular pigment—absorb blue light peaking at 460 nm. An average amount of macular pigment filters out about 40% of blue light incident on the macula.

    Hypothetically, increasing macular pigment would improve contrast between a background consisting of blue haze and a target, thereby increasing visual range and improving discernibiltiy of a target’s low-contrast internal details.

    The crystalline lens blocks ultraviolet (UV) radiation between about 300 and 400 nm. Over time, the damage caused by radiation, oxidation, and post-translational modification increases light scatter, fluorescence, and spectral absorption, especially at the short-wavelength end of the visible spectrum.

    As a consequence, a 53-year-old lens transmits about 70% of visible blue light, while a 75-year-old lens transmits about 25% of blue light.

    Early IOLs did not include chromophores to block UV radiation, but by 1978 researchers realized that UV radiation was damaging retinas in eyes implanted with these lenses, and by 1980 most IOLs contained UV-blocking chromophores.

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