INTRODUCTION: Like skin, hair is ageing and one of the most noticeable signs of this phenomenon is the loss of pigmentation or canities. The etiology of hair greying is still unclear but grey hair is believed to occur either from insufficient melanin formation due to melanocyte degeneration or a defect in melanosomal transfer to keratinocytes. Risk factors associated with canities include some auto-immune disorders but also external causes such as stress, nutritional deficiencies to mention just a few. Because canities equally affect both women and men and can appear in the late thirties in many persons, it constitutes an important aesthetic concern and consequently a market for cosmetic companies. In our laboratory, we had previously used digital photography to successfully substantiate the anti-canities activities of hair treatment. In these studies, images were acquired with a large photographic bench. The aim of this study was to investigate how the multi-purpose handheld Antera 3D®, camera (Miravex, Dublin, Ireland) can be used to more easily monitor the reversibility hypopigmentation of hair of the effectiveness of camouflage techniques such as hair dying in the context of in vivo cosmetic testing.
METHODS: Photographs of the mid-scalp area of Asian subjects were acquired with either the handheld Antera 3D®, camera or with a photographic system developed by the Spincontrol company called Visio-Face®, which allows to accurately reposition the subjects and to reproduce similar lighting and photographic conditions. This system is based on a Nikkon D300 reflex digital camera equipped with a Pro micro Nikkor AF 2.8/60 mm lens (Nikon Corporation, Tokyo, Japan) associated with two flash lights Elinchrom style 600 RX flashes (Elinca SA, Renens, Switzerland). The analysis of grey hair was done on regions of interest of approximately 4 cm2 through the L*a*b* colour space coordinates. These L*a*b* values were directly given by the Antera 3D® software or mathematically converted from the RGB values constituting the digital photographs by a piece of software developed by Spincontrol. Additionally, experiments were carried out by mixing increasing numbers of white human virgin hair taken from hair tresses with natural black hair of subjects in vivo in order to test the capabilities of the Antera 3D® method over a large range of grey hair conditions. Data from the Antera 3D were investigated for reproducibility, repeatability, correlations with other imaging techniques and ability to detect small changes in hair greying severity.
RESULTS: Among the variables investigated (L*a*b* and the Individual Typology Angle ITA°), the Luminance L* was found to be the most sensitive parameter for the quantification of grey hair severity. Repeatability of hair L* values determined with the Antera 3D® software in subjects exhibiting varying degrees of canities were between 1.1% and 2.2%. Reproducibility of hair L* values determination ranged between 1.1% and 4.7%. Repeatabilities of hair L* values determined from digital photographs were found to be in the range 0.2%-5.3% and reproducibilites between 0.2% and 2.5% depending on canities severity. Good correlations were observed with digital photographs analyzed using Spincontrol proprietary software.
DISCUSSION AND CONCLUSION: Antera 3D® represents a reliable tool for the quantitative measurement of the hair greying phenomenon. Reproducibility, repeatability and sensitivity were found to be very satisfactory and results correlated well with chromametry measurements or Luminance L* determination obtained by image analysis of photographs acquired with more sophisticated benchmarks. Therefore Antera 3D® is a reliable, cost- and time-effective method to measure differences in hair grey intensity before and after cosmetic interventions.