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Coaxial Illumination

When properly worn and carefully chosen, coaxial illumination may enhance not only visual acuity, but also proper posture.

The physical stress of clinical dental hygiene practice is an occupational risk factor for developing musculoskeletal disorders (MSDs). Coaxial illumination, combined with magnification, can improve visual acuity, ergonomics, and diagnostic capabilities for oral health professionals.1–3 A quality light source and magnification will reduce strain on the eyes and the need to lean in closer to the oral cavity, improving posture.


Dental hygienists work in the small, dark area of the oral cavity, limiting visual acuity. A good lighting system can help improve practitioners’ ergonomics, reduce fatigue, and is essential for optimizing visual performance and comfort. A study related to nursing and medication dispensing errors found that adequate lighting was one of the top environmental solutions for avoiding mistakes.4 The clinical dental hygienist needs to detect slight tissue changes and pathology even more intricate and tiny than medication labels.

The purpose of clinical illumination is to help oral health professionals see the oral cavity and anatomical features clearly while in a comfortable working posture. Good clinical illumination should provide the following:5

  • Prevent the clinician from being forced into poor working postures
  • Help see the detail and color of the point of interest
  • Enable control of light intensity
  • Reduce eye strain and pain


Traditionally, the light used to illuminate the oral cavity during treatment has been an overhead light on a track or a chair-mounted light, neither of which provides significant benefit to visual acuity. Studies have found that overhead lighting is often out of reach, causing the clinician to use awkward postures to reach it, and it frequently cannot be adjusted with one hand.6,7 Study results also showed that overhead lighting provided inadequate luminance levels for the operating field.6,7 Iacomussi et al8 analyzed the effects of overhead lighting on dental hygienists. They found that this type of lighting created overhead glare, illuminance (brightness) and luminance (distribution) levels that were too high or too low, and luminance (distribution) uniformities that were too high or too low.8While overhead lights are typically adequate for illuminating flat objects, they are less effective at illuminating deeper body cavities, like the oral cavity.5

The increased interest in enhancing visual acuity and desire to reduce MSD risk have increased the popularity of coaxial illumination. Coaxial illumination is a type of lighting that provides a parallel source of light, reducing the incidence of shadows in the field of vision.3 During clinical practice, dental hygienists easily block their source lighting, compromising neck and back ergonomics (Figure 1). This problem is eliminated because coaxial illumination provides a target source of light.

With coaxial illumination, lights are usually directly mounted to custom-fitted loupes. A variety of styles, weights, and types of lights are available. Cordless versions are also on the market. No matter what type of light, the purpose of coaxial illumination is to enhance visual acuity, aiding dental hygienists in their intricate work. A properly designed illumination system should provide a uniform beam, constant beam pattern within the clinicians’ working range, high detectability of anatomical features, and no glare.5 The recent advances in light emitting diode (LED) technology have made coaxial illumination more efficient.

Coaxial Illumination
FIGURE 1. This clinician is working in an awkward position, which is exacerbated by poor lighting.


LED lighting has become an excellent source of illumination in the dental field. LED lights are extremely small, lightweight, and provide a high-quality light source with greater output than traditional light sources and better color rendering.9 These are desired qualities in a mounted light as correct brightness and true color allow for more clear vision and may even make tissue and anatomic changes more discernable during dental hygiene diagnosis and treatment. However, the greatest output is not necessarily the safest.10 Hawes et al11 demonstrated that LED lighting provided the best visual acuity as measured on symbol identification and color recognition compared with fluorescent lighting.


Finding the light that best supports ergonomic practice is important. LED headlights are classified into four types according to how the light beam is generated: single lens optic, reflective optic, single lens/reflective optic, and achromatic multi-lens optic.5 Single lens optics are not uniform, contain blue light around the main beam, and their beam patterns and color uniformity fluctuate with changes in working distance. Achromatic multi-lens optics offer uniformity in beam patterns and color.5

LED lights come in varying colors: neutral white, cool white, and extreme cool white. It is important to evaluate the beam uniformity and color rendering before choosing a light. Shine the light on a white piece of paper to check for uniformity. The edges of the beam should not appear ragged or fading. Check the color rendering by illuminating anatomical objects to make sure they are true to color. In order to see accurate colors, consider an LED light with a neutral white color, or a color that accurately portrays the anatomical structure.5 The intensity of the beam should also be considered, as too high an intensity could cause a glare, which is potentially harmful to the clinician and patient. Too low of an intensity may lead the clinician to hunch or lean forward, or even strain the eyes to see more clearly. A light with an adjustable beam intensity may eliminate many of these issues. Ask the manufacturer about the photobiological standards of the LED light and what risk category the light falls under. The light’s weight and size should be considered, as a light that is too heavy or cumbersome may force the clinician into unhealthy postures or even harm vision.


Dental hygienists are at an increased risk of MSDs. Proper lighting can help reduce these risks and help clinicians maintain ergonomic positioning. Coaxial illumination using LED lights can offer proper distribution and color rendering. Oral health professionals should consider the beam, color, weight, and size before introducing a light into clinical practice. Future research needs to look into different types of lights, the beams and colors produced, and how they affect vision and the visual inspection of the oral cavity during dental hygiene diagnosis and treatment. When properly worn and carefully chosen, coaxial illumination may enhance not only visual acuity, but also proper posture.


  1. Holt ER, Hoebeke R. Shine a light. Dimensions of Dental Hygiene. 2012;10(9):25–27.
  2. Bly J, Jordre BD. Improve visability. Dimensions of Dental Hygiene. 2015;13(1):21–33.
  3. Branson B, Simmer-Beck M. Visual acuity without injury. Dimensions of Dental Hygiene. 2009;7(9):48–49.
  4. Mahmood H, Chaudhury H, Gaumont A, Rust T. Long-term physical environments-effect on medication errors. Int J Health Care Qual Assur. 2012;25:431–441.
  5. Chang BJ. Ergonomic benefits of surgical telescope systems: selection guidelines. J Calif Dent Assoc. 2002;30:161–169.
  6. Knulst AJ, Mooijweer R, Jansen FW, Stassen LP, Dankelman J. Indicating shortcomings in surgical lighting systems. Minim Invasive Ther Allied Technol. 2011;20:267–275.
  7. Matern U, Koneczny S. Safety, hazards and ergonomics in the operating room. Surg Endosc. 2007;21:1965–1969.
  8. Iacomussi P, Carcieri P, Rossi G, Migliario M. The factors affecting visual discomfort of dental hygienist. Measurement. 2017;98:92–102.
  9. Kralikova R, Wessely E. Lighting quality, productivity and human health. Available at: Accessed May 28, 2018.
  10. Assessing the Photobiological Safety of LEDs. Available at: Accessed May 28, 2018.
  11. Hawes BK, Brunye TT, Mahoney CR, Sullivan JM, Aall CD. Effects of four workplace lighting technologies on perception, cognition and affective state. Int J Ind Ergon. 2012;42:122–128.

From Dimensions of Dental HygieneJune 2018;16(6):22-24.

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