Near-infrared confocal microscopy is a new tool that provides skin images in vivo, with high resolution and contrast at a specific depth. Regional variations in live human skin viewed by confocal microscope have not been studied so far. In vivo reflectance confocal microscopy was performed in 10 adults (eight males, two females) of various skin phototypes. Six topographic sites were studied in each subject: forehead, cheek, inner and outer forearm surfaces, lower back and leg. Epidermal thickness at suprapapillary epidermal plates and rete pegs was measured during real-time imaging and the number and diameter of epidermal keratinocytes in each epidermal cell layer as well as the characteristics of dermal papillae were defined from the grabbed images. Stratum corneum appeared brighter in sun-exposed than in sun-protected areas and particularly pronounced in heavily pigmented individuals. The epidermal thickness at rete pegs, but not the suprapapillary epidermal plate, was greater in sun-exposed areas than in sun-protected sites except forearm flexor surface. The en face numerical density of granular keratinocytes is greater on the face as compared with all other sites, whereas the surface density of spinous keratinocytes is greater on sun-protected sites. Additionally, the number of basal keratinocytes per millimeter length of dermoepidermal junction is greater in sun exposed areas. Interestingly, the dermal papillae shape varies and their sizes increase in circumference from sun-exposed to sun-protected sites, as observed at a specific depth below the stratum corneum. In summary, our results demonstrate that near infra-red reflectance confocal microscopy is a feasible tool for microscopic analysis of skin morphometry in vivo.

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Background and Objectives: Fractional photothermolysis is a new concept in cutaneous re-modeling whereby laser-induced microscopic zones of thermal injury (MTZMicroscopic Treatment Zones) are surrounded by normal, viable tissue. This unique thermal damage pattern allows re-epithelialization in less than 24 hours. To increase patient comfort level during the procedure of fractional photothermolysis, simultaneous skin cooling has been proposed and is now extensively used. The purpose of this in vitro study was to examine the influence of skin temperature on the diameter of the epidermal microthermal zone and the extent of thermal injury per unit area. The determination of the changes in these parameters that are due to skin temperature will allow the better control and understanding of fractional photothermolysis at different skin temperatures. Materials and Methods: Fractional photothermolysis was performed with a 1,550 nm fiber laser (Fraxel SR 1 Laser) with 10 mJ per pulse on full-thickness cadaver skin. The skin samples were brought prior to exposure to temperatures that ranged from 0 to 458C. The epidermis of the skin samples was separated by dispase treatment, stained for thermal damage by NBTC stain, and lesion diameter was assessed by a blinded investigator. Results : The average MTZ diameter exhibits a positive, linear relationship with skin temperature (R 2 ¼ 0.904, P < 0.0001). As the skin temperature increases from 0 to 458C. The MTZ diameter increases from 93 to 147 mm (58%), and the MTZ area from 6,870 to 17,050 mm 2 (148%). Conclusion : The skin temperature affects the size of epidermal MTZs during fractional photothermolysis and is an important variable factor. The use of simultaneous skin cooling increases patient comfort; however, as it also decreases MTZ size, it may interfere with treatment efficacy. The control of skin temperature is necessary to provide a consistent outcome and to be able to compare treatments.