Principles and application of optical coherent tomography in dermatology.

measurement of the skin especially to monitor epidermal thickness during clinical trials: • study of the effect of UVA1 and UVB on epidermal thickening [6] ; • study of age-related skin changes [7] . It is more suitable than high-frequency ultrasound to explore the epidermis and dermo-epidermal junction. In this issue of Dermatology , Mogensen et al. [8] used an OCT system developed at Risoe National Laboratory, Denmark, to describe the morphology of normal skin and measure skin structures. This hand-held OCT probe used is very interesting because it is easy to handle compared to the first OCT generation. The probe is applied directly to the skin, the scanning lasts few seconds and it is easy to be used on children and at different anatomical sites. The authors present a descriptive study with a small cohort of 20 volunteers (6 months to 59 years old) with interesting results, but unfortunately, reproducibility of the measures has not been discussed. OCT is a technique that has nearly reached maturity. The recent development of a system using femtosecond lasers with low coherence provides in vivo images that are close to those obtained by classical histological techniques. Such systems are not yet available for daily dermatological use, but several published studies show that the information that they can provide is valuable especially with regard to the epidermis and the dermal-epidermal border.