Avinash Konkani: What to Look for in Medical Lights

When I work on medical equipment planning, I often come across the issue of how best to differentiate between the medical lights for exam, procedure, and surgical rooms. We know that the lighting needs of a room where a major surgery is taking place are different from one that is used for a routine exam, but I’m not aware of any guidelines or studies that describe what kind of lighting is needed for each use.

When considering lighting, you need to take into account the following:

• Illuminance measures the total amount of light per unit area. The unit used to describe illuminance is “flux,” which is lumens (total light output) per square meter. Sufficient illuminance is essential to being able to see the objects clearly.
• Radiance is the measure of total radiant intensity per unit of projected area. This is measured in watt per square meter steradian (watt/m² sr). This is an important factor because, if not controlled, it may cause the patient to burn.
• Color Rendering Index (CRI) is a measure of how much the given light source can illuminate an object’s colors as compared to a reference light. The CRI scale varies from 0 to 100 CRI (and can also be negative). If the CRI scale of the light source is higher, that means the ability of the given light source to illuminate the natural colors of the viewing objects is also higher. This is an important factor in the medical field, because the color of an object under examination is one of factors that clinicians use in their diagnosis or treatment.
• Color Temperature (Lighting Color Scale) measures the appearance of light from the light source. This is measured in Kelvin (K) on a scale ranging from 1,900–10,000 K. Higher Kelvin values mean that the light source emits whiter light, with 10,000 K being the equivalent to a blue sky.

Are there any other factors that needs to be considered to differentiate between these three types of lights? If you know any documents that provides guidelines to differentiate between the different types of medical lights used in the hospital, please let me know.

Avinash Konkani, Ph.D., AHFP., is senior clinical engineer at Beth Israel Deaconess Medical Center, a teaching hospital of Harvard Medical School, in Boston, MA. He serves on different committees of AAMI and ACCE and he is a ABET Program Evaluator (PEV).