The prevalence of myopia has risen rapidly in recent decades and is largely attributable to our changing lifestyles. Early visual experiences can affect the axial growth of the eye but just how this occurs is not clearly understood. In this review, we discuss the evidence which supports the protective effect of time outside on myopia and why it is likely that exposure to natural daylight is responsible. We compare how artificial indoor lighting differs from daylight in brightness, colour spectrum and flicker, and how these factors influence growth of the eye. We discuss why periods of home confinement during the COVID-19 pandemic have led to further increases in the prevalence of myopia among young children, and how optometrists should advise people seeking to delay the onset or slow down the progression of myopia in their children.