Natural day light is good for us; particularly the bright light of the day – or ‘blue light’- in the shorter wave length spectrum (460 nm). This blue light helps set our internal body clocks via special light receptors in the eyes and keeps us in sync with the day-night cycle and our everyday activities which revolve around this – simply known as our circadian efficiency. Too little blue light – or too much of it at the wrong time of day – disrupts the internal body clock, which in turn can lead to serious health problems including depression, cancer, heart disease and diabetes (Holzman, 2011). Older people are particularly susceptible to body clock disruptions owing to the aging lens of the eye which begins to deteriorate – and yellow - in middle age onwards and reduces the transmission of blue light to the light detecting cells in the retina. Because older people are also less physically active the problem is confounded because, generally, they are not getting sufficient exposure to blue light outdoors in order to compensate for the reduced transmission capacity of the aging lens. This paper firstly, sets out the literature context for a study of the non-visual effects of blue light and reports on two exploratory studies exploring effects in older people where the aging of the eye lens has led to cataracts. The first study shows the positive effects of increasing blue light transmission in patients with cataracts on sleep patterns and cognitive function involving complex (rather than simple) reaction time tasks (Schmoll et al, in press). The post operative data was collected 12 days post surgery, suggesting a fairly immediate improvement. The second study is currently exploring the effects of yellow versus clear intraocular lens implants – which have different blue light transmission capacities – in patients with cataracts (n=60) and any differences in sleep outcomes and cognitive reaction times post-surgery. We will discuss the findings in relation to future research designed to explore the effects of artificial blue light exposure versus natural daylight on circadian efficiency in older people.