Insight into the Role of Photoreception and Light Intervention for Sleep and Neuropsychiatric Behaviour in the Elderly
Light exerts influences on many physiological and behavioural functions in humans. These functions can be described as image-forming (IF) and non-image forming (NIF) visual processes, both originating in the retina of the eye. Image-forming refers to vision; the process of detecting
and distinguishing shapes and colour of objects. Non-image forming refers to detecting level of light intensity or brightness of ambient space, which affects basal physiology such as cycles of rest and activity or the endocrine system. Rod and cone photoreceptors in the outer retinal layer
are most important for imageforming vision, while non-image forming functions depend upon additional input from the photopigment melanopsin, which is expressed in retinal ganglion cells (RGC) that makes these cells photosensitive (pRGC). Projections of these pRGCs convey light-induced electrical
impulses to a number of brain regions. Visual acuity and colour contrast naturally diminishes with age but dementia often has major effects on the visual processing systems, which impact on the quality of life. The ability of humans to manipulate their light exposure has the immediate potential
to either create problems with human physiology (as in shift workers) or to compensate physiological disadvantages (of IF and NIF visual impairment). This mini-review describes the impact of aging on the function of the eye with respect to nonimage forming effects of light, summarises light
intervention studies for sleep and neuropsychiatric symptoms and considers implications from photoreceptor-weighted light intensities for biologically effective light intervention and lighting solutions for patients with dementia.
Keywords: Alzheimer; Sleep; circadian; cognitive impairment; melanopsin; photoreception; retina; visual impairment
Document Type: Research Article
Publication date: 01 October 2017
This article was made available online on 31 July 2017 as a Fast Track article with title: "Insight into the Role of Photoreception and Light Intervention for Sleep and Neuropsychiatric Behaviour in the Elderly".
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