Correction: The effect of sex and age on facial shape directional asymmetry in adults: A 3D landmarks-based method study.

[This corrects the article DOI: 10.1371/journal.pone.0288702.].

Body mass index is an overlooked confounding factor in existing clustering studies of 3D facial scans of children with autism spectrum disorder.

Cluster analyzes of facial models of autistic patients aim to clarify whether it is possible to diagnose autism on the basis of facial features and further to stratify the autism spectrum disorder. We performed a cluster analysis of sets of 3D scans of ASD patients (116) and controls (157) using Euclidean and geodesic distances in order to recapitulate the published results on the Czech population. In the presented work, we show that the major factor determining the clustering structure and consequently also the correlation of resulting clusters with autism severity degree is body mass index corrected for age (BMIFA). After removing the BMIFA effect from the data in two independent ways, both the cluster structure and autism severity correlations disappeared. Despite the fact that the influence of body mass index (BMI) on facial dimensions was studied many times, this is the first time to our knowledge when BMI was incorporated into the faces clustering study and it thereby casts doubt on previous results. We also performed correlation analysis which showed that the only correction used in the existing clustering studies-dividing the facial distance by the average value within the face-is not eliminating correlation between facial distances and BMIFA within the facial cohort.

The effect of sex and age on facial shape directional asymmetry in adults: A 3D landmarks-based method study.

OBJECTIVES: Facial directional asymmetry research, including age-related changes, is crucial for the evaluation of treatment of craniofacial malformations/trauma in orthodontics, facial surgery and forensic sciences. The aim was to describe facial directional asymmetry (DA) in different age categories of adults using 3D methods. According to our hypothesis, facial shape DA (1) depends on sex; (2) differs among age groups; and (3) has wider variability in older age. MATERIAL AND METHODS: A cross-sectional sample of healthy Czech adults without craniofacial trauma or anomalies consisted of 300 3D facial models (151 females). The age-range in the study was between 20-80 years. The shape asymmetry of 28 3D landmarks was evaluated using geometric morphometrics and multivariate statistics. RESULTS: The manifestation of DA was similar in both sexes and in each age category; however, there were some statistical differences. In contrast to the ideal symmetrical face, the mean asymmetrical faces tended to create a slightly bent "C" shape of the midline. Therefore, the upper face was rotated slightly clockwise and the lower face counter-clockwise. The right eye was located slightly higher, with the nasal tip and mandibular region tilting to the left. Sex differences in facial DA were significant before the age of 40. DA was more significant in the youngest males than in the oldest, while the women's DA did not change. CONCLUSIONS: The DA patterns were similar in both sexes and in all age categories (a slightly bent C shape of the midline); however, some significant local differences between male age groups were found. A significantly more pronounced asymmetry compared to other age groups was found only in the youngest males from 20 to 40 years. Moreover, significant sexual dimorphism of DA rapidly decreased after middle age, likely caused by the same age-related changes of the face during aging.

Morphometric Assessment of Facial Morphology in Infants with Orofacial Clefts up to two Years of Age: A Three-Dimensional Cross-Sectional Study.

OBJECTIVE: To assess modelled facial development of infants with unilateral cleft lip (CL) and cleft lip and palate (UCLP) compared to controls up to two years of age. DESIGN AND PARTICIPANTS: A total of 209 facial images of children (CL: n = 37; UCLP: n = 39; controls: n = 137) were obtained in four age categories (T0 = 0.2-0.5; T1 = 0.6-1.0; T2 = 1.1-1.5; T3 = 1.6-2.0 years) and were evaluated using stereophotogrammetry and geometric morphometry. All patients underwent lip surgery before T0, patients with UCLP underwent palatoplasty (T0, T1 before palatoplasty; T2, T3 after palatoplasty). RESULTS: In patients with CL, the forehead was significantly retracted (p ≤ 0.001), while the supraorbital and ocular regions were prominent (p ≤ 0.001). The oronasal region appeared convex (p ≤ 0.001). The lower lip and chin were non-significantly protruded. In patients with UCLP, a significantly retracted forehead and prominent supraorbital region were apparent (p ≤ 0.001). A retrusive oronasal region (p ≤ 0.001) was observed in the middle face. The chin was anteriorly protruded (p ≤ 0.01). No progression of deviations was found with increasing age. After the first year, a slight improvement in the morphological features became apparent. The shape variability of the clefts and controls overlapped, suggesting a comparable modelled facial development. CONCLUSIONS: The facial morphology of individuals with cleft was comparable to the norm. Shape deviation was apparent in the oronasal region, forehead, and chin, which minimised with increasing age even in complete clefts.

Three-dimensional analysis of modeled facial aging and sexual dimorphism from juvenile to elderly age.

A detailed understanding of craniofacial ontogenetic development is important in a variety of scientific disciplines dealing with facial reconstruction, forensic identification, ageing prediction, and monitoring of pathological growth, including the effect of therapy. The main goals of this study were (1) the construction of the facial aging model using local polynomial regression fitting separately for both sexes, (2) evaluation of the aging effect not only on facial form as a whole but also on dimensions important for clinical practice, and (3) monitoring of the development of shape facial sexual dimorphism. Our study was based on the form and shape analysis of three-dimensional facial surface models of 456 individuals aged 14-83 years. The facial models were obtained using a structured light-based optical scanner and divided (for some analyses) into four age categories (juveniles, young adults, middle adults, and elderly adults). The methodology was based on geometric and classic morphometrics including multivariate statistics. Aging in both sexes shared common traits such as more pronounced facial roundness reducing facial convexity, sagging soft tissue, smaller visible areas of the eyes, greater nose, and thinner lips. In contrast to female faces, male faces increase in size until almost 30 years of age. After the age of 70, male facial size not only stagnates, like in females, but actually decreases slightly. Sexual dimorphic traits tended to diminish in the frontal and orbitonasal areas and increase in the gonial area.

Three-dimensional mixed longitudinal study of facial growth changes and variability of facial form in preschool children using stereophotogrammetry.

OBJECTIVES: Since the normal, non-pathological facial growth in preschool children is not sufficiently reported, the aim was to follow growth changes of facial surface, sex differences and facial variability in preschool children using 3D stereophotogrammetry. SETTINGS AND SAMPLE POPULATION: Mixed longitudinal sample of healthy Caucasian preschool children without head and facial trauma or craniofacial anomalies from 3.4 to 6.7 years of age consisted of 25 girls and 17 boys. MATERIALS AND METHODS: 136 3D facial models from optical scanner Vectra 3D were evaluated by geometric morphometrics (CPC-DCA, PCA, per-vertex t test). RESULTS: In both sexes, the lower face was widened and elongated, and the prominences of the superciliary arches, lower orbital region, nose, lips and chin increased. Facial surface increments were more even in girls with a maximum between the fourth and fifth year of age, while in boys, there was the most intensive growth between fifth and sixth year of age. Sexual dimorphism was very stable during investigated period, only less statistically significant at the age of 3 years. Boys had more prominent lateral lower part of forehead, nose and lips than girls in every age category. CONCLUSIONS: The longitudinal growth of the face between third and sixth year of age was similar in both sexes, facial sex differences were found in terms of intensity, size and timing. Variability of facial form showed that boys' faces were larger on average and facial shape did not differ. The knowledge of facial growth is essential for diagnostics and clinical practice.

Three-dimensional assessment of facial asymmetry in preschool patients with orofacial clefts after neonatal cheiloplasty.

OBJECTIVES: To evaluate facial asymmetry changes in pre-school patients with orofacial clefts after neonatal cheiloplasty and to compare facial asymmetry with age-matched healthy controls. METHODS AND MATERIALS: The sample consisted of patients with unilateral cleft lip (UCL), unilateral cleft lip and palate (UCLP), and bilateral cleft lip and palate (BCLP). The patients were divided in two age groups with a mean age of 3 years (n = 51) and 4.5 years (n = 45), respectively, and 78 age-matched individuals as controls. Three-dimensional (3D) facial scans were analyzed using geometric morphometry and multivariate statistics. RESULTS: Geometric morphometry showed positive deviations from perfect symmetry on the right side of the forehead in the intervention groups and the controls. The UCL groups showed the greatest asymmetric nasolabial area on the cleft-side labia and the contralateral nasal tip. The UCLP group showed, moreover, asymmetry in buccal region due to typical maxillar hypoplasia, which was accentuated in the older group. The BCLP groups showed slightly similar but greater asymmetry than the control groups, except for the philtrum region. CONCLUSIONS: Asymmetry of each of the cleft groups significantly differed from the controls. Except for the buccal region in the UCLP and BCLP groups, asymmetry did not significantly increase with age.