Having optimal vision is vital in radiology, so it’s important to reduce any eye fatigue – and ambient light can have a large effect on this. Eye fatigue – apart from being uncomfortable – can also temporarily degrade one’s vision. The quality of human vision is incredibly varied – depending on environmental factors as mentioned earlier, and also on physiological factors. The ideal reading room should have an ambient lighting to match the monitor screen. Additionally, before beginning work, a radiologist should allow their eyes to adjust for about 15 minutes 2 to bring their vision to the optimal level. One study 1 has shown that ambient lighting below 7 lux is too dark, and over 100 lux is too bright, so regardless of which recommendation is followed – ambient light must not be too dark or too bright. However the European guidelines for quality assurance in breast cancer screening diagnoses recommends 20 lux or less. In general it is recommended that the ambient lighting matches the brightness of your screen – which is stated to be 20 to 40 lux when the screen is at a brightness of at least 350 cd/m 2 (or 420 cd/m 2 for mammography), as per the American College of Radiology guidelines. So, when you look back to your screen you will no longer have optimal vision until several minutes have passed. Despite your eyes adjusting to the screen, as soon as you look away to a brightly lit wall, light or object – your eyes will begin readjusting to this change in contrast. This is relevant in the reading room, because if the screen and the ambient light are quite different (either brighter or darker) your vision will constantly be readjusting between the ambient light and the screen each time you look away from the screen. You have probably experienced this yourself either entering or exiting a tunnel or dark room, and know that it takes several minutes until you can clearly see again in a new environment. However after several minutes the eyes will re-adapt to this brighter environment.Ĭonversely, if your eyes are adjusted to a sunny environment and you suddenly go into a dim tunnel, everything darker than the dark objects in the sunshine will suddenly appear black. If adapted to a dark tunnel, suddenly exiting will cause you to be momentarily blinded with white. Anything brighter than the dim light would automatically register as ‘white’ to your vision – thus when you step outside you will suddenly be blinded because the majority of objects will be brighter than anything in the tunnel.Įyes adapt to the brightness level of one’s environment. This is because in the dim tunnel, the darkest objects become ‘black’ to your perception, and the bright objects – for example the dim light coming the ceiling – become ‘white’ to your perception. When you suddenly exit into the sunshine outside, most objects will be brighter than the bright objects in the tunnel, so they will appear as a bright white to your vision. For example when in a dim tunnel you will be able to see most things clearly. At any one time, the human eye can detect a contrast ratio of 1000, however this ratio is not definite, but rather relative. The most major way that ambient light can reduce contrast is by affecting the eyes’ ability to adapt to a certain level of light. However these can be minimized by using anti-reflective coatings on the screen, and positioning the monitor in such a way that light does not directly reflect onto the screen. This can be distracting and reduces the contrast at that specific location. Specular reflections and glare: Light is reflected onto the screen directly from an external light source, or reflected off of an object, causing glare or a ‘specter’ of the object to appear on screen. The most obvious ways would be:ĭiffuse Reflections: Light is reflected uniformly across the screen, whitewashing the blacks on screen. But even with a high contrast monitor, one little thing can greatly reduce contrast: ambient light.Īmbient light can reduce contrast in several ways. Most medical monitors aim to provide high contrast screens, which is certainly the first and most important way to increase contrast. The higher the contrast, the more differences in shades our eyes are able to see. When viewing medical images, one of the most important factors for accurate diagnosis is contrast. But why is it so important? Read on to learn the major reasons why ambient light is important, and how you can achieve the optimal reading room. Controlling ambient lighting in reading rooms is vital to ensuring that radiologists are able to see scans and notice potential problems as optimally as possible.
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