A morphometric study of age- and sex-dependent changes in eyebrow height and shape^✰

Summary

Background

Rejuvenation procedures of the periorbital region and the forehead, with the eyebrow as a key structure, are often performed in plastic surgery. There is no common consent on the changes of aging in this region and the consecutive treatment options. This study was designed to support the body of literature with a broader data basis about the natural changes of eyebrow position and its shape.

Methods

The brow shape, the lid axis, and the distance between both medial canthi (DMC) were analyzed retrospectively on randomly selected standardized photographs of healthy Caucasian females and males. Six defined heights of the upper brow border, including the position and height of the highest brow point (HBP) and the angle of the upper brow line, were measured.

Results

A total of 244 Caucasian females and males in two groups (<34 years and >55 years) were analyzed. The data showed a difference between brow shapes of young females and males, especially relating to the HBP, which is located medially in young females. The brow shape of females assimilates toward a male shape with aging. The eyebrow moves upward, the DMC widens, and the lid axis drops laterally in both sexes with aging.

Conclusions

Our data suggest that rejuvenation procedures should focus on not only lifting the brow but also reshaping and stabilizing the brow, especially the HBP, which plays an important role in defining the upper brow line. Our findings can explain why lifting the brow can create not only an undesired surprise but also an older look.

Introduction

Rejuvenation procedures have ever since relied on trying to reverse the changes in facial anatomy, which are caused by facial aging and, in turn, are described by theories of facial aging. To achieve a natural result, the performed changes have to move the individual back to a point earlier in time. Thus, the correct description of the exact changes that occur over time is of paramount importance in facial plastic surgery. Yet, the precise description of these changes with aging has proven to be challenging.1, 2 This is due to the complex anatomy, a high degree of interindividual and ethnical variations, and a varying understanding of facial harmony or beauty.² In the upper face, it is particularly difficult to define changes with aging.¹ There is a constant presence of dynamic alterations that take place as part of the mimic and compensation processes for static changes of facial structures over time,³ the latter being the main reason for compensatory elevation of the eyebrow position by frontalis muscle activation to antagonize the ptotic brow during aging.³ This process makes the static evaluation of the upper facial third particularly difficult and leads to differing results of studies trying to observe the exact changes of this facial area.4, 5, 6, 7

Although the main concept of most rejuvenation procedures of the upper face relies on an elevation (“lifting”) of the respective facial structures and several groups including our own have shown that different surgical procedures succeed in achieving this goal,8, 9, 10, 11, 12, 13, 14, 15 the underlying aging process is yet to be fully understood. The fact that some studies show the opposite effect during upper facial aging – the rising of the eyebrows – may be an explanation why the sometimes possibly overaggressively applied forehead lifting has led to unsatisfactory results, which present as an unnatural appearance or transport an unintended mimic expression (e.g., surprise).⁸ The resulting lifted and surprised look might be the main reason for an observable decrease in popularity of these procedures and a more critical approach to upper facial rejuvenation. Again, the media and beauty industry seem to transport a changing ideal in recent years rather than the overly high and arching eyebrow with a maximum of distance between upper lid border and brow.¹⁶

To better understand the physiological “behavior” and age-dependent changes of the upper face, this study was designed to support the literature body with a broader data basis about the natural changes of eyebrow position and its shape in a large study cohort of Caucasian subjects. To our knowledge, thus far, there is no such study evaluating the age-dependent changes in the eyebrow height and shape in a comparably sized study group in both sexes.

From a database, all eligible patient photographs from the Department of Plastic and Hand Surgery Department, University Medical Center Freiburg, Germany, were selected for evaluation. Pictures were taken from July 1996 to November 2014. Inclusion criteria were defined as Caucasian subjects, male and female, age between 15 and 82 years, a standardized full-frontal photograph with fully opened eyes, a straightforward gaze, and a relaxed facial expression. Exclusion criteria were injuries, scars, and Botox injections or surgeries of the upper facial half as well as syndromic and congenital abnormalities, facial paralysis, and all other known conditions, which might interfere with the measurements. All patients provided informed consent for the participation, and the principles outlined in the Declaration of Helsinki have been followed in this study.

Photographs were analyzed using Photoshop (©Adobe Systems, Inc., San Jose, California), and all anatomical points were selected manually. A line between both medial canthi was drawn, and the distance between both medial canthi (DMC) and the projection of the distance between the medial and lateral canthus on the DMC plane (ICD) was measured. Furthermore, for both eyes, distances from the DMC-plane to the upper border of the brow were measured at defined positions (H1: 1/4 ICD, H2: 1/3 ICD, H3: 2/3 ICD, H4: ICD, H5: 6/5). The highest brow point in reference to the DMC-plane was defined on the arch of the upper eyebrow border. Its distance from DMC was measured and recorded as HBP. Again, the horizontal deviation laterally from the medial canthus (Ax) was measured on the DMC. As this was a retrospective study, no markers for calibration could be placed on the original photographs. Therefore, all measured distances were standardized in relation to the white-to-white distance (WTW), which can be normalized by age as described by Rüfer et al.¹⁷ (see Figure 1).

In addition, two angles were measured: the angle between the DMC plane and the intercanthal plane (angle α) and the angle that is formed by the upper border of the eyebrow ascending to the HBP point and the upper border of the brow that descends from HBP laterally (angle β). (See Figure 2)

Four groups were defined: female young “f(y)”, male young “m(y)”, female old “f(o)”, and male old “m(o)”, see Table 1. Statistical evaluation was performed using Student's t-test or if the normality test failed Mann-Whitney-White rank-sum test (Past 3 Statistics Software package, University of Oslo, Hammer, Ø., Harper, DAT, Ryan, PD 2001). As there was no statistically significant difference between the data of the left and right eyes, the data were merged and analyzed together. Statistical evaluation was completed by a linear regression analysis, which was performed for each distance and angle (Past 3) using age as a variable. To illustrate the results of the linear regression in a compressed manner, the y-values for H1-H5, HBP, and Ax on the regression line for ages 20 and 70 years are presented. Differences with a p-value smaller than 0.05 were considered as statistically significant and values lower than 0.001 as highly significant.