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The short wavelength, i.e., blue light, is crucial for non-image forming effects such as entrainment of the circadian system in humans. Moreover, many studies showed that blue light enhances alertness and performance in cognitive tasks. However, most scientific reports in this topic are based on experiments using short exposure to blue or blue-enriched light, and only a few focused on the effects of its reduced transmittance, especially in longer periods. The latter could potentially give insight into understanding if age-related sleep problems and cognitive decline are related to less amount of blue light reaching the retina, as the eyes' lenses yellow with age. In this study, we investigated the effects of prolonged blocking of blue light on cognitive functioning, in particular-sustained attention and visuospatial working memory, as well as on sleep, and melatonin and cortisol levels. A group of young, healthy participants was randomly allocated to either blue light blocking or control group. Depending on the group, participants wore amber contact lenses, reducing the transmittance of blue light by ∼90% or regular contact lenses for a period of 4 weeks. No changes were observed for measurements related to sleep and sleep-wake rhythm. Dim light melatonin onset, evening levels of melatonin, and morning cortisol answer did not show any significant alterations during blue light (BL) blockade. The significant effects were revealed both for sustained attention and visuospatial memory, i.e., the longer blocking the blue light lasted, the greater decrease in performance observed. Additionally, the followup session conducted ∼1 week after taking off the blue-blocking lenses revealed that in case of sustained attention, this detrimental effect of blocking BL is fully reversible. Our findings provide evidence that prolonged reduction of BL exposure directly affects human cognitive functioning regardless of circadian rhythmicity.

A cataract is an opacity (clouding) of the normally clear lens which develops as a result of aging, metabolic disorders, trauma or heredity. The number of patients with cataract is increasing exponentially. This disease requires surgical intervention, to remove the cloudy lens and to introduce the eye lens polymer. In this work we will present analyses of degraded parts of human lens. Experimental materials were obtained from the lens removed during surgical intervention. These biological samples were measured using Almega XR Confocal Raman spectrometer (Thermo Scientific) with an excitation source of 785 nm laser line. The Raman vibrations in the spectral region of 650-1750 cm −1 were analyzed. The difference spectra revealed an excess of tryptophan, tyrosine, phenylalanine, β-sheet conformation, and molecules or molecular groups.

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