Lighting designed to meet the special needs of the aging or diseased eye is especially critical in health care facilities, senior care homes and outdoor lighting in public spaces. The following list summarizes the lighting factors that deserve special attention (IESNA, 2007):
Task Illuminances – Older eyes require increased task illumination which should be adjustable to suit both the eye and the particular task. It is also important not to have excessive contrast between the task and the background. Magnification of the task may be required to compensate for reduced visual acuity.
Light source color rendering – Use daylight or lamps with a minimum color rendering index of 80, and preferably higher, to help distinguish between object colors and reveal the intensities of colors.
Lighting uniformity and contrast – Uniform light distribution and relatively high reflectance matte surfaces moderate strong shadows and improve visibility of space and surroundings.
Disability glare – Glare which reduces the visibility of people and objects should be eliminated by the shielding or the careful aiming of bright light sources. Potential reflections from shiny surfaces such as floors, furniture, TVs or computer terminals, and glare from bright windows, emergency lighting, and other light sources should be considered when planning improvements.
Discomfort glare – Glare from luminaires or bright windows which causes annoyance or discomfort may be reduced via dimming or by modifying shields or shades.
Adaptation – Plan for transition zones between dark and light areas to allow a sufficiently long time for older eyes to adapt. While younger eyes can adapt in seconds, older eyes often require minutes to adapt, especially when moving from light to dark.