I. Semi-quantitative scoring system
1. Visual evaluation: This method is simple and does not need any equipment. Generally, a unified scoring standard is formulated first, and the researchers directly score the wrinkles in various anatomical parts of the subject's face. This method is suitable for large-scale epidemiological investigation [2]. In this way, we investigated the facial wrinkles of 1004 18 ~ 68 Han women. It was found that the eyes, wrinkles and mouth areas began to appear at the age of 20 ~ 25, 26 ~ 30 and 36 ~ 40 respectively. The most obvious age groups are: 25 ~ 40 years old, 30 ~ 45 years old, 40 ~ 55 years old [3].
2. Photo grading: Take facial photos under uniform standard conditions, and grade the wrinkles on the photos according to pre-established standards. For example, 45 photos on the front and 45 photos on both sides are used to grade wrinkles in many parts of the face [4]. This method is convenient for retrospective comparative study, but it can only observe the two-dimensional structure of skin wrinkles and is easily influenced by filming conditions and techniques. At present, this method is widely used in the literature reports of wrinkle curative effect evaluation.
3. Scoring of microscopic skin silicon mold: First, make a silicon mold of skin texture, observe the surface texture of skin silicon mold with a microscope (× 10), and semi-quantitatively score the thickness and pitch of skin texture according to the grade scoring method [5]. On this basis, in recent years, various types of dermoscopy have been developed to directly observe the skin texture in vivo, and its effect needs to be verified clinically.
Second, the objective quantitative evaluation system
Although the semi-quantitative method is economical and simple, it is easily influenced by subjective factors and is mainly used to observe facial wrinkles. It is difficult to distinguish between skin texture changes (such as primary lines and secondary lines), skin roughness and skin texture. Skin profilometry developed by mechanics and optics is used to scan living skin or silicon model of skin, and the scanned image is digitized by computer image system. Not only can the skin wrinkles be quantitatively evaluated, but also the above wrinkles can be quantitatively evaluated, which is the development direction of the three-dimensional structure research of skin surface in the future.
1. Common skin contour measurement technology: (1) mechanical skin profilometry. This technology comes from international standards for evaluating metal surface characteristics. The cone-shaped diamond pen tip slides in the horizontal direction of the skin silicon mold at a uniform speed of 65438 0 mm/s, and the vertical displacement of the pen tip in the groove and microprotrusion is converted into an electrical signal by the sensor, and the skin area of 2.5 mm×2.5 mm is measured mechanically with high precision. Many instruments based on this principle have been developed for 20 years. Because the scanned image is clear (figure 1), it is still the gold standard for comparing other skin contour measurement techniques. The disadvantages of this method are trouble and time-consuming, and the scanning speed is too slow to detect deep wrinkles [6]. ⑵ Optical profilometry. This method is based on detecting reflected light, which depends on the depth and angle of wrinkles. Comprises the following steps: reflecting a sample by a parallel light source with a fixed incident angle, generating shadows with different widths along with the depth of wrinkles, recording by a camera, and calculating the average density and average depth of wrinkles by a simple trigonometric method; At the same time, the shape of microprotrusion is calculated. The measuring area is 6.4 mm×6.4 mm, and the theoretical resolution under 50 times magnifying glass is 12.5 micron [7]. ⑶ Laser profilometry. Using the optical principle, it involves autofocus and triangulation system. A diode laser is used to focus on a point of the replica, so that the reflected light is focused on a detector. When the silicon mold of the skin moves, any change in texture will cause zooming and change the light intensity received by the detector. The main advantage of the system is that it can measure deeper surface lines and use high scanning speed to make the measurement time shorter [8]. ⑷ Interference fringe projection. An image system with a digital micromirror device emits light to the skin surface, and the image is recorded by a special camera. Three-dimensional images are generated by gradual analysis method of temporary phase shift to reconstruct skin surface texture. It can scan the silicon model of skin or directly scan the living skin. The examined skin area is larger, and deep wrinkles can be scanned (Figure 2). The scanning speed is faster without touching the sample, but the scanned image is not as clear as the mechanical profiler [9, 10]. 5] * * * Focusing laser microscope technology (confocal scanning laser microscope). * * * focused laser scanning microscope is composed of * * * focusing system and traditional electron scanning microscope, with laser with wavelength of 488 nm as light source. Based on the longitudinal optical cutting technology, the microscope can scan different layers of skin replica, generate parallel cross-sectional figures, and provide clear two-dimensional or three-dimensional images and corresponding quantitative parameters simultaneously [1 1]. The resolution of X/Y axis is 0.2 micron, and the resolution of Z axis is 0.4 micron. The observation area of reflective * * * focusing microscope is 250μ m× 250μ m, and the depth is 200μ m. The brightness and thickness of stratum corneum, the minimum epidermal thickness, the cell area of granular layer, the thickness of basal layer and the number of dermal papillae per unit area can be observed [12]. [6] Transparency profilometry. Very thin, especially the blue dyed silicon mold has light transmission characteristics. Insert the blue-dyed silicon mold into a special device that emits parallel light, and place a camera with 752×582 pixels on the other side. The depth of the groove is converted into a picture represented by 256 gray levels. Wrinkles with a depth of 20 ~ 300 μ m2 can be calculated by corresponding software. The development and evaluation of samples can be completed in a few seconds, but it is more troublesome to make skin silicon molds [13].
Figure 1 forearm obtained by mechanical skin profiler
Inner skin surface image: thick lines show first-order lines; Thin lines represent minor lines.
Fig. 2 Deep forehead wrinkle image obtained by interference fringe light reflection skin profiler.
2. Parameters describing the skin contour: The main parameters come from the standard parameters describing the metal surface. Skin protrusions are not as regular as metal, and complex microprotrusions are anisotropic. The characteristics of skin surface cannot be limited to analyzing a section in one direction. The parameters describing skin contour need to calculate not only the average value of wrinkles scanned many times, but also the values in many directions. Therefore, the dermatoglyphic parameters are more than 10[ 14]. The most commonly used paRameter in literature is ra, which represents skin roughness: the arithmetic average of pitch profile up and down the baseline; Depth parameter Rz representing dermatoglyphics or wrinkles: the average vertical distance between the highest pitch point and the lowest dermatoglyphics point. With the improvement or update of equipment, many new parameters [12, 13] are put forward.
Third, the application in medical beauty
1. Study on related factors of skin aging: There are many reports on the correlation between smoking and sun exposure and skin aging. Yin et al. [15] reported that the analysis of the medial dermatoglyphics of 63 volunteers found that the vertical distance and groove depth from the highest point to the lowest point of dermatoglyphics of smokers were significantly higher than those of non-smokers, and the number of primary and secondary dermatoglyphics was significantly lower than that of non-smokers. The analysis of female facial wrinkles shows that amenorrhea is a risk factor of facial wrinkles, and sunscreen is a protective factor to prevent facial wrinkles [3]. The interference fringe light projection technique was used to study the inside of the forearm in the relative light protection area, and it was found that the skin roughness increased obviously with age, which confirmed that in addition to external environmental factors, time-course aging was also an important cause of skin aging [9].
2. Evaluation of the efficacy of anti-aging drugs: Since 1995, the US Food and Drug Administration (FDA) approved 0.05% tretinoin cream to treat skin photoaging, there have been many clinical reports on the efficacy of tretinoin. In order to reduce the side effects such as rough skin, Nyirady et al. [16] treated with 0.02% tretinoin cream for 24 weeks, fine lines and skin texture were obviously improved, and skin tolerance was increased. However, the course of treatment is too long, which reduces the compliance of patients. After 5 weeks of treatment with 1% ~ 5% tretinoin cream twice a week, wrinkles and skin texture were obviously improved and the course of treatment was shortened. People with type I ~ II skin have better curative effect. Fitzpatrick et al. [17] observed that the growth factor gel containing 8 bioengineering sources was externally applied twice a day for 60 days, and the skin roughness Ra value was obviously reduced and the skin texture was improved by optical skin profiler. Heckmann et al. [18] observed 30 patients who received botulinum toxin A injection to correct facial expression lines, recorded the range of facial expression before and after treatment with a digital camera, recorded the eyebrow movement with computer assistance, and observed the muscle paralysis. Four doctors independently evaluated the series of photos semi-quantitatively, which can better reflect the effect of botulinum toxin A on upper facial wrinkles than subjective self-evaluation.
3. Evaluation of curative effect of light rejuvenation: Various peeling or non-peeling laser or strong light rejuvenation is a new treatment content developed in recent years. Optical skin profilometer was used to evaluate the treatment of facial wrinkles and scars by short-pulse CO2 laser. It was found that the measurement results of skin profilometer were consistent with the improvement of clinical score and the increase of dermal collagen, which provided objective evidence for the effectiveness of this method [19]. Bisson et al. [20] molded the wrinkles around the mouth with silicone rubber, and observed the depth of wrinkles with a simple optical microscope. 3 1 case of CO2 photo-rejuvenation was evaluated before operation, 6 weeks after operation and 2 years after operation. The results showed that the wrinkle depth decreased by 965,438 0% after 6 weeks, and still decreased by 87% after 2 years. Recently, the curative effect of intense pulsed light has attracted people's attention, but there are still many reports about the operator's evaluation of the photos before and after treatment or the patient's subjective feelings [2 1, 22]. Some people have analyzed the 1 1 documents of five kinds of laser non-exfoliative rejuvenation, and found that the evaluation methods of curative effect are mostly influenced by subjective factors, so it is difficult to compare the therapeutic effects of this new technology [23].
Fourth, look to the future:
With the development of medical aesthetics and cosmetology, new technologies and methods of skin aging care and treatment are constantly introduced. How to evaluate its curative effect and objectively compare it with various new technologies and methods has become a research hotspot in the field of beauty, which has promoted the study of biological characteristics of human skin surface and the quantification of three-dimensional structure. Although the semi-quantitative method of skin texture is easily influenced by subjective factors, it is difficult to quantitatively evaluate fine contours, but it is economical and simple, and will continue to be used in wrinkle treatment evaluation or epidemiological research for a certain period of time. The objective quantification of skin surface photometer evaluation system has attracted more and more attention and admiration from researchers. With the continuous improvement and improvement of this technology, the price will drop and gradually become the main means to evaluate the skin surface texture and wrinkles.