An analysis of the visual behaviour of dental hygienist.

The visual behaviour of a dental hygienist is very critical: the practitioner is exposed to very high luminance levels, for long time doing heavy visual task with very small details, crucial colour perception and risk of damaging the patient condition in case of mistake. A typical dental hygienist visual behaviour was deeply characterised in terms of relevant photometric quantities. The two most important quantities are: illuminance and luminace. In order to characterise the visual conditions of the practitioner luminance maps of his field of view were acquired with a luminance calibrated CCD (Charge Couple Device) detector. The luminance maps showed high contrast zones that produce glare at the eyes of practitioner. The contrast is the description of differences in luminance between an object and its background and is one of the two fundamental aspect for vision. The team applied a procedure (2) based on CIE General Disability Glare Equation (3), to evaluate veiling luminance (a parameter describing the physiological origin of disability glare) that causes contrast degradation and visual fatigue, versus the degradation of Ratio of Contrast (Rc perceived contrast over intrinsic contrast). This research demonstrated that the normative requirements are not sufficient to assure the best perceptive conditions for dental hygienist to prevent performances degradations and long-term fatigue.