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Asymmetry of the face is a common finding that had been discussed in a variety of fields including art, poetry, philosophy and medicine. In the surgical literature, facial asymmetry in general and the laterality of this observation, described mostly as a casual note, without profound discussion. In our study, we hypothesis that, facial asymmetry in the normal unbiased population has a unique laterality appearance.
Patients and methods
A consecutive series of 315 patients included in the study, all had anterior facial digital pictures taken in the same technique and loaded on Image J Software™. Four measurements were taken from the midline, to right and left sides; in the middle face to the Zygoma point and in the lower face to Gonion point. The results given by pixels were loaded on excel sheet, office 2016 software™, processed and analyzed by Spss software™.
Using the paired T-test. Middle and lower third of the face in the right side had a significant dominance size wise with p-value < 0.019 and < 0.039 respectively.
Our study results support our main hypothesis and strongly demonstrate right side, size wise, dominance in the middle and lower face.
. However, a well-documented research work, did not began till the Renaissance era, when Leonardo da Vinci elucidated his theories and ideas in a vast number of manuscripts regarding human proportions and his quest for the ideal facial proportions
. Great number of prominent Italian art masters made enormous contributions to the understanding of human beauty and symmetry, such as Michelangelo and Raphael; continued in the last 300 years with writers, philosophers, and scholars, emphasized the rational and scientific knowledge which led to the neoclassical canon's proportions
In the modern scientific and medical literature, facial appearance was thoroughly investigated, studied, and presented in variety of publications, all include the inevitable knowledge that all of us, the humans, have some degree of asymmetry
. The asymmetry was measured using different reference structures, from skeleton measurements as in the extensive innovative work of Farkas on the cephalometric studies, continued by variety of publications at all surface levels
Over the last 20 years, the authors examined facial structure in thousands of patients and raised the hypothesis that facial asymmetry is not arbitrary but rather had unique repetitive laterality. The purpose of this study was to explore the clinical observation by the authors, means that facial asymmetry in the normal unbiased population has a unique repetitive pattern between right and left, and discuss some implications of the findings.
Materials and methods
A consecutive series of 500 patient frontal facial pictures treated by the surgeons for variety of facial procedures, enter the study. The pictures were taken by digital Nikon camera with 60 mm macro lens from the same distance. Any patients, that according to the medical file, the chief complain was facial asymmetry, had prior injections for facial contouring enhancement during the last 12 months, prior facial surgeries, significant dental, or orthodontic work performed and or significant\morbid obesity; were excluded off the study. The pictures were loaded on Mac computer and measuring performed by using an Image-J software™. The Image-J software transformed the digital camera data into measurable pixels, means that accurate measurement can be applied without the fear that slight distance difference between the object and the lens may alter the measurements. The midline divider was a straight line drawn between Glabella – Nasion – SubNasale – Menton, and the reference points were right and left Zygoma points, (1 and 2 respectively) and right and left Gonion points (3 and 4 respectively) - see figure one, all can easily be found, draw, and marked on frontal picture with minimal (if at all) bias or question, whether is the right point. Following, four measurements that were taken in 90 degrees to the midline divider, measured by pixels, loaded on excel sheet office 2016 software™ converted the data into Spss software™ allow analyzing the data by our statistical consultant. (Figs. 1 and 6)
Following implementation of all the exclusions criteria, 315 patients enter the study process; 250 females and 65 males with age range from 21 – 65 with 34 years old on average. Using the paired T-test, in the middle and lower third of the face, the right side has a significant definitive dominance with p-value < 0.019 and < 0.039 respectively. (See Table 1). Figure 2, Figure 3, Figure 4, Figure 5 demonstrate few patients measurements.
Table 1Facial measurements in pixels included in multivariate analysis.
In our study, midline was based on well-established external landmarks connected by straight line, which can easily be found and marked on frontal picture with minimal if at all bias or question where is the right point
. The statistical analysis shows clearly and significantly and is in line with our hypothesis of right-side lateralization dominance. We found that the right side is dominant over the left side, size wise in both the middle face (M right= 738.60, SD=249.53, M left= 692.81, SD=239.15, t (315) = 2.35, p<0.019) and the lower face (M right= 570.47, SD=209.72, M left= 536.58, SD=202.36, t(315) = 2.06, p<0.039). These finding to our best knowledge were not discussed nor published ever in the medical English literature; however, in the artistic literature the left side get dominance over the right, without statistical significance
Facial appearance and symmetry are the outer reflection of the inner structures, the skeleton, including teeth, muscles of mastication, muscles of expression, subdermal fat and the Bichat fat pad. As we observe from vertex caudally, we have more structures involved in contouring the outer shape. At the zygoma point we have bone, muscle and fat; and in the gonion reference point we add to the equation the teeth and the occlusion, which are more subjected to dental changes, so it reflects more diversity in the measurement; and as a result we notice a reduction in the power of the statistical power in the right laterality dominance (p < 0.039) comparing to the middle face (p < 0.019)
The soft tissue components contain skin, fat, and muscle, has various ethnic differences, but since all our patients were Caucasians and we exclude significant obese patients, these three elements have minimal effects on results deviation
. Although studies suggest that the left hemi-face is more expressive of emotions, means the expression muscles in the left side are more active, it did not over roll our findings of right-side dominance size wise
. In 1938, Fink published his study entitled “the right eye dominance”, does it impose unnoticed tilt of the face? We carefully examine the frontal pictures and could not find any findings to support it
. Our study analyzed our own crude data as appears in patients files. In the effort to explain the findings we did extensive search in the literature even for possible factors such as right or left handedness and new genetic published studies; and could not find any solid relation to the right-side dominance size wise we found.
In conclusion, our study results, strongly support right side size dominance at the middle and lower face, findings that can help with patient's interaction by providing them solid information regarding the inherited asymmetry that we all have; and help in the process of explaining the expected results of facial procedures including major and minor surgical procedures, fillers and other procedures since we all have some degree of inherited lateral asymmetry; further studies will be helpful to elucidate the factors induces our findings.
We declare that patients consent for photo publication in the manuscript was given in writing without exception.
Conflict of interest
Farhad B N
Facial aesthetics: concepts and clinical diagnosis facial aesthetics: concepts and clinical diagnosis.