Effects of Ambient Light
Excessive ambient lighting can have a negative effect on visualization of normal and abnormal structures on digital dental radiographic images. Ambient light reflects off the front surface of the display increasing luminance in dark areas of the image reducing the contrast ratio. Bright light also interferes with the eye's ability to adapt fully to luminance emitted from the image, thereby reducing the discriminating property of the eye and limiting visualization of subtle changes in radiographic density. The medical literature is repleat with studies that support this conclusion.
Three medical radiology guidelines have been proposed to minimize the effect of ambient light levels on radiographic interpretation of digital images. The World Health Organization (WHO) suggested that ambient light levels should be less than 100 lux at 30 cm from the display. The Commission of the European Communities (CEC) guidelines recommend a level below to 50 lux at 100 cm from the display. Finally, a joint recommendation from the American College of Radiology (ACR), American Association of Physicists in Medicine (AAPM), and Society for Imaging Informatics in Medicine (SIIM) that an ambient light level should be as low as feasible without turning the light off completely (20 - 40 lux is recommended).
A review of the dental literature reveals relatively few references on the effects of ambient light on radiographic detection tasks. Hellèn-Halme and co-workers concluded that the diagnostic accuracy of dentinal carious lesions was significantly higher in ambient light of less than 50 lux (Hellèn-Halme et al. 2008). McIlgorm et al. investigated whether calibrating a consumer grade display according to the DICOM PS3.14 would affect the presentation of dental radiographs, and whether there are any differences in the presented radiograph quality between a DICOM-calibrated consumer grade and medical display when displaying 8-bit radiographs including both intraoral and panoramic radiographs (McIlgorm et al. 2013, McIlgorm & McNulty 2015). They concluded that calibrating consumer grade display devices to comply with the DICOM PS3.14 can improve the presentation of dental radiographs. They also concluded that a DICOM-calibrated consumer grade monitor is capable of displaying an image quality that is equally preferred to a DICOM-calibrated medical grade monitor for 8-bit dental radiographs. In these studies the ambient light level was set between 25 lux and 40 lux. Odlum et al. (2012) reported that the use of the DICOM GSDF significantly improved the diagnostic accuracy in endodontic and periodontal diagnostics of intraoral radiographs under 20 to 40 lux. Some studies have reported that ambient light conditions play a significant role in affecting the interpretation of digital radiographs (Arnold 1987, Patel et al. 2000, Haak et al. 2002). Kutcher et al. (2006) showed that the diagnostic accuracy was significantly higher when using hooded laptops compared to bright conditions (Kutcher et al. 2006). Also Hellèn- Halme & Lith (2012) found that it was easier to detect dental caries in dim ambient light <50 lx than on consumer grade LCD displays with or without a hood in bright ambient light >1000 lx (Hellèn-Halme & Lith, 2012). When comparing enamel caries, there was no difference between dim and bright ambient light (Hellèn-Halme & Lith 2012). Pakkala et al. (2012) compared bright with dim lighting conditions using consumer grade and medical displays (Pakkala et al. 2012). In their report, the observers achieved higher sensitivities with lower illuminance settings than with higher illuminance settings. However, this was accompanied by a reduction in specificity, which meant that there was no significant difference in overall accuracy in detection of enamel caries lesions in intraoral radiographs. In addition, Hellén-Halme & Lith (2013) found that there was no difference between dim conditions and bright conditions when the display was calibrated to DICOM PS3.14 standards (Hellén-Halme & Lith 2013).
While no guidelines have been established for ambient light levels in dentistry, it is clear that scientific evidence suggests that for primary interpretation of digital dental radiography, ambient light should be kept as low as possible around 25 - 50 lux. Secondary interpretation for operative and reference viewing should be less than 350 lux.
To provide monitoring of ambient light levels in the dental office start using the RightLight Monitor.
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