THE IMPACT OF HUMAN-CENTRIC LIGHTING PARAMETERS ON OLDER ADULT’S PERCEPTION, AND COGNITIVE PERFORMANCE

Population aging is a prominent demographic challenge. Older adults face increased risks of sleep dysfunctions, depression, and cognitive impairments due to physical, biological, and psychological factors associated with aging. These behavioral issues elevate safety risks at home, which necessitates the transition to assisted living facilities. Extensive research highlights the influence of healthcare environmental design, particularly related to architectural lighting impacts on residents' well-being and quality of life. To optimize older adults' health and well-being, it is essential to consider both the visual and non-visual effects of architectural lighting. Visual impacts include parameters related to task performance and visual acuity, while non-visual impacts may include outcomes such as circadian rhythm regulation, sleep quality, mood enhancement, and cognitive performance, thereby emphasizing the importance of implementing a holistic conceptual approach to human-centric lighting in indoor environments.While existing gerontology studies have primarily focused on light-level attributes, such as radiant flux, illuminance, and equivalent melanopic lux, there has been limited exploration of spectral and spatial pattern parameters in indoor lighting. The primary objective of this research is to investigate the impact of both quantitative and qualitative aspects of lighting design, including spatial layout characteristics such as uniformity, direction, centrality, and spectral attributes like correlated color temperature (CCT), on the visual perception, preference, mood, cognitive performance, and overall well-being of older adults in assisted living facilities. The study employed a multi-method approach across three main research phases. In phase I, a Q-sort survey involving 60 participants assessed the impact of diverse spatial light patterns on visual perception and preference. In phase II, a within-subject design evaluated the cognitive performance of 32 older adults in similar lighting scenarios within real and virtual environments. Lastly, in phase III, the study examined the relationship between spatial and spectral light patterns and cognitive performance through virtual reality testing with 32 participants. Results revealed significant effects of different spatial light patterns on older adults' environmental impressions, including visual preference, stress levels, and cognitive performance. Uniform and indirect lighting were preferred, with no substantial differences between peripheral and central spatial arrangements of light layers. Non-uniform lighting induced a relaxed impression, while uniform lighting heightened perceived stress. Furthermore, the study demonstrated the suitability of virtual reality environments (VR) for assessing cognitive performance and subjective perception. The findings underscore the substantial influence of spatial and spectral light patterns on the cognitive performance of older adults in assisted living facilities. This research contributes to the understanding of the visual and non-visual effects of human-centric lighting on the well-being of older adults. By considering spatial and spectral light attributes, designers can enhance cognitive function, reduce impairments, and cultivate healthier and more efficient living environments

Cataract, macular characteristics and assessing lens opacities

Age-related macular degeneration and cataract are very common causes of visual impairment in the elderly. Macular pigment optical density is known to be a factor affecting the risk of developing age-related macular degeneration but its behaviour due to light exposure to the retina and the effect of macular physiology on this measurement are not fully understood. Cataract is difficult to grade in a way which reflects accurately the visual status of the patient. A new technology, optical coherence tomography, which allows a cross sectional slice of the crystalline lens to be imaged has the potential to be able to provide objective measurements of cataract which could be used for grading purposes. This thesis set out to investigate the effect of cataract removal on macular pigment optical density, the relationship between macular pigment optical density and macular thickness and the relationship between cortical cataract density as measured by optical coherence tomography and other measures of cataract severity. These investigations found: 1) Macular pigment optical density in a pseudophakic eye is reduced when compared to a fellow eye with age related cataract, probably due to differences in light exposure between the eyes. 2) Lower macular pigment optical density is correlated with thinning of the entire macular area, but not with thinning of the fovea or central macula. 3) Central macular thickness decreases with age. 4) Spectral domain optical coherence tomography can be used to successfully acquire images of the anterior lens cortex which relate well to slit lamp lens sections. 5) Grading of cortical cataract with spectral domain optical coherence tomography instruments using a wavelength of 840nm is not well correlated with other established metrics of cataract severity and is therefore not useful as presented as a grading method for this type of cataract

Design for aging eyes: an in-depth look at fast-food outdoor menu displays

The aging population, one of the fastest growing age groups in the United States, is an audience that graphic designers and visual communicators often fail to address. Fast-food menu displays are just one example of a design that may not meet the needs of a senior clientele. This study consolidates and summarizes a variety of literature relevant to the design needs of an aging population.;This study then poses four research questions: (1) How can we design a fast-food menu for the aging eye? (2) How can a designer understand the functional problems associated with the visual and motor deficits of the older population? (3) What colors do elderly have difficulty seeing? What typeface is easiest to see at a distance? (4) What size does that typeface have to be in order for it to be read without any difficulty?;By considering the changes that occur as the eye ages, the fast-food industry could take a giant step forward. Two basic conditions must be met in order to make fast-food menu displays more legible and effective. The first condition is that the material (text & photographs) on the menu should be both visible and legible. The second condition is that the items on the menu must be easily understood. To test the current fast-food menu displays, 90 individuals responded to a questionnaire. The questionnaire provided data that begins to reveal how people order food from the menus at fast-food restaurants. The same questionnaire also collected some qualitative data regarding individuals\u27 overall impressions of fast-food menu design. The outdoor menu displays of four drive-thru fast-food restaurants were also evaluated and analyzed based on criteria established by the literature review.;Results from the study provided some answers about what individuals like and want in the designs of fast-food menus. Speed and consistency were two suggestions that were reported by multiple respondents on the surveys. Also, there seemed to be a strong preference for pictures. The findings from the menu analysis show that there is not a universal standard in terms of outdoor fast-food menu display design.;The purpose of this line of research is to produce some preliminary guidelines for the structure, organization, and design layout of outdoor drive-thru fast-food menu displays. The study establishes critical legibility factors related to aging vision and analyzes the displays of four fast-food restaurants

Understanding disability glare: the effects of scattered light on visual performance

The focus of this thesis is on how light is scattered on its passage through the optics of the human eye, and the consequences for visual performance under different lighting conditions. A number of visual psychophysical measurement techniques were employed to investigate the impact of light scatter on various aspects of visual performance. The preliminary experiments carried out were designed to explore the physical properties of scattered light in the eye. Scattered light varies in both amount and angular dependence, outcomes that relate directly to the number and size of particles involved. In this respect, scattered light is estimated using two methods: one that measures both the amount and the angular dependence of scattered light and the other that assumes constant angular dependence in all observers. The findings show that there are significant differences in angular dependence between observers and that the size of the differences correlates with errors in the estimation of the overall amount of scatter. Experiments were then carried out to investigate the effects of increased scattered light on visual performance and whether these can explain any aspects of age-related visual degradation. To disentangle increased scattered light from the innumerable other changes that occur with ageing, the amount of scattered light in young, healthy eyes was increased using fogging filters. Increased scatter is shown to have only a small effect on chromatic sensitivity and the ability to recognise letters or other high contrast optotypes that are commonly used to assess visual acuity. Contrast sensitivity, on the other hand, can be much reduced in the presence of increased light scatter

New investigations into macular pigment optical density

Macular pigment (MP) is the collective name for three carotenoids, lutein, zeaxanthin and meso-zeaxanthin, which are found at high concentrations in the central macula. The macular carotenoids, like all carotenoids, are entirely of dietary origin. The term ‘macular pigment optical density’ (MPOD) refers to the peak concentration of MP in the retina, which varies from one individual to the next and is measurable in vivo. On account of its blue-light-filtering and antioxidant properties, MP has become a subject of interest with respect to age-related macular degeneration (AMD), the hypothesis being that MP helps to protect against AMD; the higher the MPOD, the lower the risk for AMD. Recently, a new MPOD-measuring device, the MPS 9000 (MPS), entered the ophthalmic market. Using this device, the research described here aimed to contribute new information to the MP literature. A second MPOD instrument, the Macular Pigment Reflectometer, was also used at times, but a reliability study (included in the thesis) demonstrated that it was unsuitable for use on its own. First, a series of exploratory investigations were undertaken to maximize the accuracy and consistency of MPOD measurements taken with the MPS; a protocol was established that substantially improved repeatability. Subsequently, a series of MPOD-based studies were conducted on anisometropia, South Asian race, blue-light-filtering contact lenses, and dietary modification with kale. The principle findings were as follows: interocular MPOD differences were not attributable to interocular refractive error differences; young adults of South Asian origin had significant gender-related MPOD differences (males>females, p<0.01), and they also had significantly higher MPOD than Caucasians (p<0.0005); wearing blue-light-filtering contact lenses for eight months did not affect MPOD; and dietary modification with kale for 16 weeks did not increase MPOD. This body of research adds new insights to MP knowledge, which in turn may contribute to MP knowledge in the context of AMD

Managing Phenol Contents in Crop Plants by Phytochemical Farming and Breeding—Visions and Constraints

Two main fields of interest form the background of actual demand for optimized levels of phenolic compounds in crop plants. These are human health and plant resistance to pathogens and to biotic and abiotic stress factors. A survey of agricultural technologies influencing the biosynthesis and accumulation of phenolic compounds in crop plants is presented, including observations on the effects of light, temperature, mineral nutrition, water management, grafting, elevated atmospheric CO2, growth and differentiation of the plant and application of elicitors, stimulating agents and plant activators. The underlying mechanisms are discussed with respect to carbohydrate availability, trade-offs to competing demands as well as to regulatory elements. Outlines are given for genetic engineering and plant breeding. Constraints and possible physiological feedbacks are considered for successful and sustainable application of agricultural techniques with respect to management of plant phenol profiles and concentrations

Carotenoid colour as a cue to health in human skin

Carotenoids are red-yellow plant based pigments. When consumed, they contribute to human skin yellowness which in turn is perceived as healthy and attractive looking. In many non-primate species, carotenoids colour sexually selected ornaments, signalling health. This thesis explores the relationship between skin yellowness and aspects of human health to test the hypothesis that carotenoid colouration of skin acts as a cue to health beyond diet. Chapter 2 presents a demonstration that a modest change in carotenoid intake can lead to a favourable change in appearance. Chapter 3 investigates the relationship between skin yellowness and a number of health related risk factors. Findings show that that psychological stress varies with skin yellowness (independent of fruit and vegetable intake) both between and within participants. Chapter 4 investigates the relationship between prior symptoms of infectious illness (e.g. cold and flus); finding that symptoms experienced during the prior eight weeks are related to skin yellowness between subjects and also within (marginally). More recent symptoms of illness (i.e. the prior week) were not reflected in skin yellowness. The final empirical chapter explores skin colour and plasma carotenoid changes with experimentally induced sickness. Plasma carotenoids were found to reflect baseline skin yellowness and showed a reduction in response to sickness but this reduction was not reflected in skin yellowness. Skin colour did change in a manner consistent with changes in blood perfusion and oxygenation status. A follow-up perceptual study confirmed that this change can reliably inform judgements of health. Taken together, findings suggest that skin yellowness is related to aspects of health beyond diet (i.e. psychological stress and prior illness) on a timescale of weeks but not days; likely reflecting the time taken for carotenoids to reach the skin. Theoretically, findings support the hypothesis that carotenoid colouration of human skin is a cue to health