Development and Validation of Photo-Numerical Scales for Facial Wrinkles on Chinese Population

Various ethnicities age differently due to intrinsic genetic factors and inherent responses to UV exposure. The unique facial skeletal structure and function of Chinese skin can result in distinct aging signs compared to those observed in Caucasians. Additionally, there are limited published photo-numerical scales for cosmetic treatments, which often yield relatively low efficacy compared with aesthetic surgery. Therefore, appropriate and sensitive clinical evaluation tools are needed to accurately assess signs of aging and the efficacy of cosmetic treatments for the Chinese population.

Develop a new set of photo-numerical scales to evaluate facial wrinkles specifically based on a Chinese population.

Four photo-numerical wrinkle scales were developed based on Visia-CR images from 5310 Chinese females aged 18-69, focusing on forehead, glabella, crow's feet, and nasolabial fold wrinkles. These 10-point (0-9) scales were rigorously validated for repeatability, reliability, and usability through inter- and intra-grader assessments conducted by multiple clinical research labs. Additionally, the correlation between these scales and objective 3D measurements from the Primos 3D instrument was analyzed. It was further assessed whether the scales were more appropriate and relevant in assessing Chinese skin wrinkles severity when compared to Caucasian skin or mixed population skin scales.

Forehead, glabellar, crow's feet, and nasolabial fold wrinkle scales were established based on the Griffith principle with a 10-point harmonious scale. Inter- and intra-grader validation data among 5 graders from different regions in China showed very high correlation scores, with ICC > 0.9 for intra-grader and ICC > 0.8 for inter-grader validation. The results indicate that the scales are highly reproducible and reliable when used by trained graders. Moreover, the grading results by naïve graders correlated well with those by expert graders, suggesting that the scales are user-friendly and easy to apply. A comparison between grading scores and Primos data revealed a strong correlation between wrinkles' volume and grading scores (r = 0.79) and between wrinkles' depth and grading scores (r = 0.82). This crucial validation confirmed that the core range of the scales (mild to moderate, the general target population for cosmetic products) is particularly effective. When compared to previously used Caucasian skin scales, the grading scores obtained from the Chinese wrinkle scales showed significantly higher mean wrinkle severity values (p < 0.001) for the same set of photos, indicating that the new scales are scientifically sound, practical, and suitable for a Chinese population.

In conclusion, the photo-numeric wrinkle scales have demonstrated strong repeatability and reproducibility, high practicality, and reliable correlation with objective measurement. Given the tremendous sample size covering various regions in China, these scales are beneficial tools to evaluate the effectiveness of cosmetic products in a Chinese population.