Welcome to question of the day #52

Eyetools question of the day #52

When advising on general lighting requirements in the house, the aim should be to remove large differences in light levels both within and between rooms. Spotlights giving a pattern of strongly highlighted and relatively shadowed areas may be striking and original to normally sighted people, but totally confusing to someone with low vision. A more even level of illumination is preferred. It need not necessarily be of very high intensity in general living areas as long as it is supplemented by good local task lighting as appropriate. Higher lighting levels are required in areas containing safety hazards such as stairs or near cookers and fires.

Good use can be made of daylight by drawing the curtains well back (being careful not to create glare) cleaning windows regularly and avoiding the use of net curtains. Chairs should be positioned near the window so that the light comes over the shoulder onto the task. Daylight is ideal for reading as it is bright and diffuse. The intensity is easily controlled by changing the distance from the window. If the person has one eye they prefer to read with it is this eye that should be on the side next to the window.

Where possible, fluorescent lights should be used to create surrounding illumination. Lights mounted against a dark background should be avoided since there will be a marked contrast between the bright light and the dark background. The dark background also means there will be a less diffuse reflection of light. Diffuse reflection from light coloured walls will help increase the surrounding illumination

The reflectance of walls in a home can range from 75% (high and good for most people with low vision) to less than 5% (low and poor for most people low vision) depending on the colour of the wall. It is important to choose wall coverings with pale matt (no-shiny) finishes which give a diffuse reflection. It is also important not to make the home featureless. Use of dark borders around doors will help with movement from one room to another without reducing the total reflected light.

Vision is poorer when the surrounding illumination is poor or when it is brighter than that of the object of concern. Work is also more fatiguing and less comfortable.

Near-uniform light levels should be achieved throughout the home. Making sure that corridors, hallways and stairs have no less than one-third to one-quarter of the illuminance of the rooms opening onto them. The ability to adapt to changes in light levels is often slowed in people with low vision. It takes longer for a person with low vision to get used to a lower or higher light level.