Whether it is a household appliance, or a smart device such as mobile phone or laptop, parameter table is a key part of showing product performance. Similarly, parameter table is also the key for us to understand the performance of surgical lights. How much do you understand the significance of these parameters? Today I will share with you the meaning of common parameters of surgical lamps.
1. Central Illuminance(Ec), or intensity we often say, is the illuminance at 1m distance from the light emitting surface in the light field centre, unit is lux. The central illumination should be between 40,000-160,000 lux. From halogen shadowless lamps to LED surgical lamps, the central illuminance is significantly improved. Is the higher intensity better? of course not! If intensity is too high, operators will feel uncomfortable during procedure.
2. Color temperature is a scale indicating the chromaticity of the light source, unit is K. In order to allow us to observe the color temperature and color changes more intuitively and meticulously, we have divided the color temperature as the below picture (pictures are collected on the Internet). As shown, color temperature of warm color is below 3300K, color temperature of neutral color light is between 3300K and 5000K, color temperature of cool color light is above 5000K. In the operating room, color temperature 3300K to 5000K neutral color light is the first choice, its light is soft and show the true color effect.
3. Color rendering index is for the purpose of distinguishing true tissue color in a cavity. The two common values are Ra (R1-R9 The average number represents the color rendering of the light source) and R9 (represents saturated red), and the color rendering index Ra should be between 85-100. The higher the CRI, the more faithful the colors will be. This is especially important for soft tissue examinations and surgical procedures. Imagine if the color rendering index of the light source does not reach the standard in the operating room, the color of the illuminated object is distorted, and the color of the blood vessel seen is not red, what will happen?
4. Light field diameter, D10 refers to the diameter of light field around the light field centre, ending where the illuminance reaches 10% of Ec. The value reported is the average of four different cross sections through the light field center.
D50 refers to the diameter of light field around the light field centre, ending where the illuminance reaches of 50% of Ec. The value of reported is the average of four different cross sections through the light field centre.
5. Illumination depth L1+L2 (mm) refers to the working distance between the point of 20% illumination intensity above and below the center point. From the point of maximum illumination, which is the center of the light field 1 meter from the light-emitting surface, the photometer is moving toward the light unit until the light intensity measured falls to 20% of the maximum value. The distance between the center and this point is defined as L1. The similarly measured distance in the direction away from the light is L2. The depth of illumination without needing to refocus is the sum of the two distance L1and L2. In the second edition of the IEC standard which is published in 2009, the threshold value was revised from 20%-60%.
6. Shadow dilution is the ability of the surgical light to minimize the effect of obstructions. The test method is to block the beam by the masks which is simulating of heads of one and two surgical operators, and measure the remaining central illuminance with and without simulating the deep lumen tube.
7. Total irradiance, unit is W/㎡. In the laboratory, the temperature rise of the irradiated surface is usually converted into irradiance measurement. The higher value of the irradiance is, the higher of temperature rise in the irradiated surface. The irradiance of a single lamp cap cannot exceed 1000W/㎡.
Through these parameters, we can easily identify the lighting performance of a surgical light. Are you clear?