Children's Visual Perception of Facial Scarring and Cleft Lip Deformity Using Eye Tracking Data.

OBJECTIVE: The purpose of this study is to determine children's perception of secondary cleft lip deformity (SCLD) using objective eye tracking technology and subjective responses on a survey to understand pediatric perceptions of facial scarring. DESIGN: Cross-sectional study of participants aged 5-17 years old. METHODS: Participants viewed images of children's faces with an eye tracking device. Sixteen images were displayed, 12 with unilateral SCLD and four with no facial scarring. Eye tracking data were obtained. Gaze samples were analyzed for areas of interest (AOIs). Immediately after viewing each image, participants answered two survey questions relating to facial asymmetry attitude toward the child pictured. For analysis, participants were divided into age groups. RESULTS: A total of 259 participants were enrolled (42.5% female). Mean age was 10.5 years and 78% identified as White. In all age groups, total fixation time was greater for SCLD compared to control images. Early elementary age children spent significantly less time assessing the nose AOI compared to other groups, and also spent the least total fixation time and had the lowest visit count on all AOIs. Subjective survey questions showed similar trends with elementary age not noticing facial asymmetry compared to older age groups. CONCLUSION: This study demonstrates the successful use of eye tracking technology in children as young as 5 years old. This study suggests that SCLD is perceived as less noticeable in elementary age children and becomes more noticeable to older groups. Understanding peer perception on SCLD from this study may impact decision on revision surgery for SCLD. LEVEL OF EVIDENCE: IV Laryngoscope, 134:2726-2733, 2024.

Brief Report: Facial Asymmetry and Autistic-Like Traits in the General Population.

Atypical facial morphology, particularly increased facial asymmetry, has been identified in some individuals with Autism Spectrum Conditions (ASC). Many cognitive, behavioural and biological features associated with ASC also occur on a continuum in the general population. The aim of the present study was to examine subthreshold levels of autistic traits and facial morphology in non-autistic individuals. Facial asymmetry was measured using three-dimensional facial photogrammetry, and the Autism-spectrum Quotient was used to measure autistic-like traits in a community-ascertained sample of young adults (n = 289). After accounting for covariates, there were no significant associations observed between autistic-like traits and facial asymmetry, suggesting that any potential facial morphology differences linked to ASC may be limited to the clinical condition.

Rapid and coarse face detection: With a lack of evidence for a nasal-temporal asymmetry.

Humans have structures dedicated to the processing of faces, which include cortical components (e.g., areas in occipital and temporal lobes) and subcortical components (e.g., superior colliculus and amygdala). Although faces are processed more quickly than stimuli from other categories, there is a lack of consensus regarding whether subcortical structures are responsible for rapid face processing. In order to probe this, we exploited the asymmetry in the strength of projections to subcortical structures between the nasal and temporal hemiretina. Participants detected faces from unrecognizable control stimuli and performed the same task for houses. In Experiments 1 and 3, at the fastest reaction times, participants detected faces more accurately than houses. However, there was no benefit of presenting to the subcortical pathway. In Experiment 2, we probed the coarseness of the rapid pathway, making the foil stimuli more similar to faces and houses. This eliminated the rapid detection advantage, suggesting that rapid face processing is limited to coarse representations. In Experiment 4, we sought to determine whether the natural difference between spatial frequencies of faces and houses were driving the effects seen in Experiments 1 and 3. We spatially filtered the faces and houses so that they were matched. Better rapid detection was again found for faces relative to houses, but we found no benefit of preferentially presenting to the subcortical pathway. Taken together, the results of our experiments suggest a coarse rapid detection mechanism, which was not dependent on spatial frequency, with no advantage for presenting preferentially to subcortical structures.

Measuring visual attention to faces with cleft deformity.

BACKGROUND: Limited data are available regarding observers' visual attention to faces with congenital difference. We implemented eye tracking technology to examine this issue, as it pertains particularly to faces with cleft deformity. METHOD: Four hundred three observers assessed 273 clinical images, while their eye movements were unobtrusively tracked using an infrared sensor. Forty-one facial images of the repaired cleft lip, 137 images of other facial conditions, and 95 images of matched controls were assessed. Twenty facial regions of interest ("lookzones") were considered for all images observed. A separate cohort of 720 raters evaluated the images for attractiveness. Observer and image demographic information was collected. Visual fixation counts and durations were computed across all 20 lookzones for all images. The effect of a variety of variables on lookzone fixation was analyzed using factorial ANOVA testing. RESULTS: Cleft-repaired faces were rated as less attractive and drew observers' attention preferentially to the affected upper lip lookzone (p<.001). Images rated as less attractive garnered greater visual attention in the cleft-affected lookzones (p<.001). The eye tracking methodology demonstrated exquisite sensitivity to laterality of cleft deformity (p<.001). Individuals reporting a personal or a family history of facial deformity fixated more on the perioral region of cleft-repaired faces than did naïve observers (p<.001). CONCLUSION: These findings highlight the utility of eye tracking measures for understanding critical variables that influence the visual processing of faces with cleft deformity. The data may provide analytical tools for assessing surgical outcome and direct priority setting during surgeons' conversations with patients.

Ptosis Sensitivity Threshold for the Lay Observer.

PURPOSE: This study aims to understand the degree to which ptosis is recognizable to a layperson. METHODS: Fifteen color drawings of a gender-neutral human face were created. Six faces exhibited right-sided ptosis (decreased margin reflex distance 1 and lengthened tarsal platform show) of 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm, respectively. Six more faces exhibited left-sided ptosis of the same amounts. The 12 ptotic faces and 3 symmetrical faces were randomly placed on three 11-inch by 14-inch sheets of paper with 5 faces on each page. Lay observers were provided 6 seconds per face to indicate whether it appeared to be asymmetrical. Statistical tests examined the observers' ability to detect asymmetry better than chance. Sex differences in correctly recognizing asymmetry in ptosis at each 0.5 mm increment were analyzed. RESULTS: One hundred thirty-one lay observers were enrolled in the study. Fifty-seven were women and 74 were men. Lay people were able to correctly recognize ptosis better than chance when the asymmetry was 1.5 mm or greater. Moreover, females were more accurate in recognizing ptosis at 1.5 mm, 2.0 mm, and 2.5 mm of asymmetry. CONCLUSIONS: Lay observers tend to recognize between 1.0 mm and 1.5 mm of ptosis on one side as being abnormal. This may have implications in the selection of candidates for ptosis surgery and the analysis of subsequent surgical outcomes.

Conscious Perception of Facial Asymmetry in a Unilateral Cleft Lip Model.

OBJECTIVE: Lip asymmetry after a unilateral cleft lip repair can be perceived as an unsatisfactory result. The objective of this study is to determine the degree of upper lip asymmetry and/or nasal alar hooding required for recognition of asymmetry in a simulated model of unilateral cleft lip. DESIGN: A model of unilateral cleft lip was created using digital morphing software to simulate asymmetries in vermilion height and nasal hooding in photographs of children. Volunteers were shown photographs for different time intervals and with varying degrees of asymmetry. Ability to detect facial asymmetry was recorded and analyzed. SETTING: This study was conducted by surveying layperson volunteers in public community settings. PARTICIPANTS: 108 layperson volunteers were randomly surveyed. MAIN OUTCOME MEASURES: The primary outcome measure was a reported lip or nose asymmetry by the volunteers. Proportions and corresponding 95% confidence intervals were obtained to estimate the probability of reporting an asymmetry at 3- and 10-second intervals. RESULTS: After 3- and 10-second exposure, labial asymmetry was perceived by ≥50% of subjects at 2 mm (62%, P = .001) and 1 mm (89%, P < .0001), respectively. Nasal asymmetry was detected by <50% of subjects at 3 seconds, but ≥50% perceived a 3-mm alteration at 10 seconds (64%, P < .0001). Photographs with combined nasal and labial modification did not lower the threshold for asymmetry perception compared to either deformity alone. CONCLUSIONS: This study is the first to determine a predictable millimeter threshold for perceived asymmetry in cleft lip deformity using a digital model.

Content Validity of Patient-Reported Outcome Instruments used with Pediatric Patients with Facial Differences: A Systematic Review.

OBJECTIVE: The aim of this systematic review was to identify patient-reported outcome (PRO) instruments used in research with children/youth with conditions associated with facial differences to identify the health concepts measured. DESIGN: MEDLINE, EMBASE, CINAHL, and PsycINFO were searched from 2004 to 2016 to identify PRO instruments used in acne vulgaris, birthmarks, burns, ear anomalies, facial asymmetries, and facial paralysis patients. We performed a content analysis whereby the items were coded to identify concepts and categorized as positive or negative content or phrasing. RESULTS: A total of 7,835 articles were screened; 6 generic and 11 condition-specific PRO instruments were used in 96 publications. Condition-specific instruments were for acne (four), oral health (two), dermatology (one), facial asymmetries (two), microtia (one), and burns (one). The PRO instruments provided 554 items (295 generic; 259 condition specific) that were sorted into 4 domains, 11 subdomains, and 91 health concepts. The most common domain was psychological (n = 224 items). Of the identified items, 76% had negative content or phrasing (e.g., "Because of the way my face looks I wish I had never been born"). Given the small number of items measuring facial appearance (n = 19) and function (n = 22), the PRO instruments reviewed lacked content validity for patients whose condition impacted facial function and/or appearance. CONCLUSIONS: Treatments can change facial appearance and function. This review draws attention to a problem with content validity in existing PRO instruments. Our team is now developing a new PRO instrument called FACE-Q Kids to address this problem.

Subjective and objective evaluation of frontal smile esthetics in patients with facial asymmetry-a comparative cross-sectional study.

AIM AND OBJECTIVES: To analyze the relationship between subjective and objective evaluations of pre-treatment posed smiles in patients with facial asymmetry and to assess the influence of dentofacial structures involved in asymmetry on the perception of smile attractiveness. SAMPLE: Thirty-five patients (25 males and 10 females) between 18 and 25 years of age with facial asymmetry were selected. MATERIALS AND METHODS: Pre-treatment clinical photographs of posed smiles were subjectively evaluated by a panel of 20 orthodontists, 20 oral surgeons, and 20 laypersons. A customized Smile Mesh program was used for objective evaluation of the same smiles. Direct comparison among three smile groups (unattractive, slightly attractive, and attractive) for different Smile Mesh measurements was carried out using two-way anova test. Additionally, linear regression was performed to evaluate whether these measurements could predict the attractiveness of captured smiles. RESULTS: Patients with 'slightly attractive' smiles had a significantly greater distance between the incisal margin of the maxillary central incisor and the lower lip during smiling. The Smile Index was significantly greater in attractive smiles. However, based on the coefficients of linear regression, no objectively gathered measurement could predict smile attractiveness. CONCLUSIONS: Attractiveness or unattractiveness of smiles in patients with facial asymmetry could not be predicted by any measurement of Smile Mesh. The presence of facial asymmetry did not significantly influence the perception of smile esthetics.

[Symmetry is beauty - or is it? The rise and fall of fluctuating asymmetry]. / Symmetry is beauty - or is it? - Grandeur et décadence de l'asymétrie fluctuante.

Fluctuating asymmetry is the stochastic, minor deviation from perfect symmetry in bilaterally symmetrical organisms. It reflects the limit of developmental precision. Such a precision can be influenced by various factors, both internal (genetic mutations, stochastic variation at every levels of development) and external (environmental influences). Fluctuating asymmetry has receive an extreme attention for the past few decades, that culminated in the 90s: it has been used as an estimator of heterozygosity, fitness, environmental stress, and widely applied to human biology, sociobiology and psychology before being more or less discredited in the early 2000s. The reasons for such an extreme popularity and then disgrace are discussed here. Far from suggesting to abandon the study of fluctuating asymmetry, we indicate some of the most promising research avenues. ‡.

Regional facial asymmetries and attractiveness of the face.

OBJECTIVE: Facial attractiveness is an important factor in our social interactions. It is still not entirely clear which factors influence the attractiveness of a face and facial asymmetry appears to play a certain role. The aim of the present study was to assess the association between facial attractiveness and regional facial asymmetries evaluated on three-dimensional (3D) images. METHODS: 3D facial images of 59 (23 male, 36 female) young adult patients (age 16-25 years) before orthodontic treatment were evaluated for asymmetry. The same 3D images were presented to 12 lay judges who rated the attractiveness of each subject on a 100mm visual analogue scale. Reliability of the method was assessed with Bland-Altman plots and Cronbach's alpha coefficient. RESULTS: All subjects showed a certain amount of asymmetry in all regions of the face; most asymmetry was found in the chin and cheek areas and less in the lip, nose and forehead areas. No statistically significant differences in regional facial asymmetries were found between male and female subjects (P > 0.05). Regression analyses demonstrated that the judgement of facial attractiveness was not influenced by absolute regional facial asymmetries when gender, facial width-to-height ratio and type of malocclusion were controlled (P > 0.05). LIMITATIONS: A potential limitation of the study could be that other biologic and cultural factors influencing the perception of facial attractiveness were not controlled for. CONCLUSIONS: A small amount of asymmetry was present in all subjects assessed in this study, and asymmetry of this magnitude may not influence the assessment of facial attractiveness.

Influence of occlusal plane inclination and mandibular deviation on esthetics.

OBJECTIVE: The aim of this study was to assess the degree of perception of occlusal plane inclination and mandibular deviation in facial esthetics, assessed by laypeople, dentists and orthodontists. METHODS: A woman with 5.88° of inclination and 5.54 mm of mandibular deviation was selected and, based on her original photograph, four new images were created correcting the deviations and creating more symmetric faces and smiles. Examiners assessed the images by means of a questionnaire. Their opinions were compared by qualitative and quantitative analyses. RESULTS: A total of 45 laypeople, 27 dentists and 31 orthodontists filled out the questionnaires. All groups were able to perceive the asymmetry; however, orthodontists were more sensitive, identifying asymmetries as from 4.32° of occlusal plane inclination and 4.155 mm of mandibular deviation (p< 0.05). The other categories of evaluators identified asymmetries and assigned significantly lower grades, starting from 5.88° of occlusal plane inclination and 5.54 mm of mandibular deviation (p< 0.05). CONCLUSION: Occlusal plane inclination and mandibular deviation were perceived by all groups, but orthodontists presented higher perception of deviations.

Influence of occlusal plane inclination and mandibular deviation on esthetics

Objective:The aim of this study was to assess the degree of perception of occlusal plane inclination and mandibular deviation in facial esthetics, assessed by laypeople, dentists and orthodontists.Methods:A woman with 5.88° of inclination and 5.54 mm of mandibular deviation was selected and, based on her original photograph, four new images were created correcting the deviations and creating more symmetric faces and smiles. Examiners assessed the images by means of a questionnaire. Their opinions were compared by qualitative and quantitative analyses.Results:A total of 45 laypeople, 27 dentists and 31 orthodontists filled out the questionnaires. All groups were able to perceive the asymmetry; however, orthodontists were more sensitive, identifying asymmetries as from 4.32° of occlusal plane inclination and 4.155 mm of mandibular deviation (p< 0.05). The other categories of evaluators identified asymmetries and assigned significantly lower grades, starting from 5.88° of occlusal plane inclination and 5.54 mm of mandibular deviation (p< 0.05).Conclusion:Occlusal plane inclination and mandibular deviation were perceived by all groups, but orthodontists presented higher perception of deviations.

Objetivo: o objetivo do presente estudo foi avaliar o grau de percepção, de leigos, dentistas e ortodontistas, quanto à influência das inclinações do plano oclusal e dos desvios mandibulares na estética facial.Métodos:uma mulher com 5,88o de desvio do plano oclusal e 5,54mm de desvio mandibular foi selecionada. A partir de sua fotografia original, quatro novas imagens foram criadas, corrigindo os desvios e criando rostos e sorrisos mais simétricos. Os examinadores avaliaram as imagens por meio de um questionário, sendo realizadas análises qualitativas e quantitativas.Resultados:45 leigos, 27 dentistas e 31 ortodontistas preencheram os questionários. Todos os grupos foram capazes de perceber a assimetria, no entanto, os ortodontistas foram mais sensíveis, sendo capazes de perceber a assimetria de 4,32o de inclinação do plano oclusal e 4,155mm de desvio mandibular (p > 0,05). Os demais avaliadores perceberam a assimetria apenas a partir de 5,88o de desvio do plano oclusal e 5,54mm de desvio mandibular (p > 0,05).Conclusão:inclinações do plano oclusal e desvios mandibulares foram percebidos por todos os grupos, mas os ortodontistas apresentaram maior sensibilidade aos desvios.

Post-traumatic Stress Disorder in Facial Injuries: A Comparative Study.

AIM: The aim of the study was to identify the presence of post-traumatic stress disorder (PTSD) in patients who had sustained facial injuries, additionally, we aimed to identify other variables that may modify the psychological response to trauma that include gender, age and presence of disfigurement post-treatment and visible scars/orthopedic injuries. MATERIALS AND METHODS: Participants comprised of 460 patients from several multinodal trauma centers in Bengaluru City, Karnataka, who had sustained facial injuries that had healed either with or without significant disfigurement or scarring and with visible/orthopedic injuries. One hundred and eleven patients of the chosen 460 had sustained nondisfiguring facial injuries while 153 patients sustained disfiguring facial injuries, 64 patients who sustained facial injury (i.e. 19.5%) were lost to follow-up and were not included in the study. One hundred and thirty-two had sustained orthopedic/visible injuries; however, in this group, 18 (i.e. 13.6%) patients were lost to follow-up and were excluded from the study. The impact of events scale (IES) was used to check the presence of PTSD. RESULTS: Statistically significant higher means of IES were present in patients with disfiguring facial injuries compared to nondisfiguring facial injuries, female patients compared to male patients, patients with disfiguring facial injuries compared to orthopedic/visible injuries and patients who were younger than 50 years of age compared to patients who were older than 50 years of age and the results observed were similar at all three study intervals (date of discharge (DOD), 1 month and 6 months postoperatively). CONCLUSION: Patients with disfiguring facial injuries had significantly higher PTSD levels compared to patients with nondisfiguring facial injuries, patients with orthopedic/visible injuries had statistically significant lower IES scores which could not be strictly termed PTSD when compared to patients with disfiguring facial injuries who had high scores of IES corresponding to high levels of PTSD and these results were observed at all three study intervals (DOD, 1 and 6 months postoperatively). Female patients with disfiguring facial injuries had significantly higher PTSD levels compared to male patients (at all the study intervals) and patients younger than 50 years of age had significantly higher PTSD levels compared to older patients.

The relationship between facial shape asymmetry and attractiveness in Mexican students.

OBJECTIVES: It has been postulated that symmetric faces are considered more attractive than asymmetric ones because symmetry may signal high quality due to developmental stability. However, other studies showed that both symmetric and slightly asymmetric faces are considered attractive. Here we aim to explore this discrepancy, beginning with the analysis of the normal prevalence of facial symmetry in a population as a necessary first step prior to any attractiveness assessment. METHODS: We collected facial landmarks from two-dimensional digital images of a sample of Mexican individuals (280 females and 285 males aged 18-68 years) that were analyzed using geometric morphometric methods. Then, we chose a subsample of 100 photographs (50 females and 50 males aged 18-27 years) selected to represent a broad range of asymmetrical variation, in order to evaluate attractiveness using a sex-opposite test. Finally, we analyzed the linear correlation between attractiveness and asymmetry. RESULTS: We found that every evaluated subject presents some degree of facial asymmetry, and that both fluctuating asymmetry and directional asymmetry were significant (P < 0.0001) components of total facial asymmetry. Fluctuating asymmetry was slightly associated with age (r = 0.0858, P = 0.0414) and there were no differences between geographical regions (P = 0.413). Attractiveness was not correlated to levels of asymmetry in either sex (males: P = 0.0973; females P = 0.7415). CONCLUSIONS: Asymmetry was a prevalent feature in the present sample, and preferences for symmetric faces were not operating in the studied population.

Distraction osteogenesis in complex facial asymmetry corrections.

This article highlights the authors' experience in the management of facial asymmetries with the use of distraction osteogenesis. It is a narrative based on the clinical experience at the Meenakshi Cleft & Craniofacial Center at Chennai.

On facial asymmetry and self-perception.

Self-perception has been an enduring human concern since ancient times and remains a significant component of the preoperative and postoperative consultation. Despite modern technological attempts to reproduce the first-hand experience, there is no perfect substitute for human, stereoscopic, three-dimensional vision in evaluating appearance. Nowadays, however, the primary tools available to a patient for examining his or her own appearance, particularly the face, are photographs and mirrors. Patients are often unaware of how cameras and photographs can distort and degrade image quality, leading to an inaccurate representation of true appearance. Everyone knows that mirrors reverse an image, left and right, and most people recognize their own natural facial asymmetry at some level. However, few realize that emotions are not only expressed unequally by the left and right sides of the face but also perceived unequally by others. The impact and effect of this "facedness" is completely reversed by mirrors, potentially creating a significant discrepancy between what a patient perceives of himself or herself and what the surgeon or other third party sees. This article ties together the diverse threads leading to this problem and suggests several ways of mitigating the issue through technology and patient counseling.

The perception of facial asymmetry using 3-dimensional simulated images.

OBJECTIVE: To investigate the perception of facial asymmetry in young adults to identify the amounts of chin asymmetry that can be regarded as normal and may benefit from correction. MATERIALS AND METHODS: Three-dimensional (3D) images of 56 individuals of mixed ethnicity were obtained and used to produce average 3D images of male and female faces. Distortion was then applied to these average faces using a 3D graphics package to simulate different amounts of chin point asymmetry. Five observer groups (lay individuals, dental students, dental care professionals, dental practitioners, and orthodontists) assessed timed presentations of 3D images, rating them as "normal," "acceptable," or "would benefit from correction." Time-to-event analysis was used to assess the level of chin asymmetry perceived as normal and beneficial for correction for each group. RESULTS: The factors influencing the perception of facial asymmetry were the degree of asymmetry and the observer group. Direction of the asymmetry and gender of the assessed individual did not affect the perception of asymmetry, except in the 4- to 6-mm distortion range. The gender of the observer had no influence on perception. There were statistically significant differences in the amounts of asymmetry that the laypeople and orthodontists considered to be normal (5.6 ± 2.7 mm and 3.6 ± 1.5 mm, respectively; P < .001) and felt would benefit from surgical correction (11.8 ± 4.0 mm and 9.7 ± 3.0 mm, respectively; P  =  .001). CONCLUSIONS: Perception of asymmetry is affected by the amount of asymmetry and the observer group, with orthodontists being more critical.

Determining the threshold for asymmetry detection in facial expressions.

OBJECTIVES/HYPOTHESIS: To quantify the threshold for human perception of asymmetry for eyebrow elevation, eye closure, and smile, and to ascertain whether asymmetry detection thresholds and perceived severity of asymmetry differ in distinct facial zones. STUDY DESIGN: Online survey. METHODS: Photographs of a female volunteer performing eyebrow elevation, eye closure, and smile were digitally manipulated to introduce left-to-right asymmetry in 1-mm increments from 0 mm to 6 mm. One hundred and forty-five participants viewed these photographs using an online survey, measuring accuracy of asymmetry detection and perceived expression unnaturalness (on a scale of 1-5). RESULTS: Photographs of facial asymmetries were correctly judged as asymmetrical over 90% of the time for 2 mm or more of asymmetry in eyelid closure, and 3 mm or more of asymmetry during smiling. Identification of eyebrow elevation asymmetry gradually rose from 23% correct to 97% correct across the range of 1 mm to 6 mm of asymmetry. Greater degrees of asymmetry were ranked as significantly more unnatural across all expressions (3 tests; X(2) (6, N = 145) = 405.52 to 656.27, all P <0.001). CONCLUSION: Thresholds for asymmetry detection vary across different zones of the face; once detected, asymmetry in eyelid position is perceived as more unnatural than asymmetries in either brow elevation or smile. These data will inform counseling of patients with segmental facial weakness and may provide more objective goals for facial reanimation procedures. LEVEL OF EVIDENCE: 4.

Patients offered orthognathic surgery: why do many refrain from treatment?

AIM: To examine factors associated with patients' decision to decline surgery. MATERIAL/METHODS: Of 470 consecutive patients referred to the University of Oslo from 2007 to 2009, a sample of 160 subjects who had not undergone surgery was identified and contacted. 236 operated patients from the same period served as a comparison group. Morphology was assessed from cephalograms and photographs, and the individuals' opinions were recorded using questionnaires. RESULTS: Dentofacial morphology represented normative treatment need and was generally similar except for a higher rate of severe negative overjet in the operated group (p < 0.001). The most prevalent reasons for declining surgery were risks of side effects, the burden of care, and a general reluctance to undergo surgery. Many un-operated subjects were dissatisfied with their masticatory function and dentofacial appearance. CONCLUSION: Informed consent to orthognathic surgery represents a challenge both to the patient and the professional. The findings imply that patients' motives and fears should be explored during consultation and that the information provided should be adapted to the potential risks and benefits related to the actual treatment.

Detection and perceptual impact of side-to-side facial movement asymmetry.

IMPORTANCE: In this study, we examined whether specific facial movements have different time-delay detection thresholds, and to what extent such side-to-side facial movement asymmetry affects subjective ratings of movement naturalness. Ratings of dynamic asymmetry in experimentally manipulated video recordings demonstrate that there are different side-to-side time-delay thresholds for distinct regions of the face, with a strong inverse correlation between naturalness rating and the length-of-time delay. These findings will be helpful for counseling patients with unilateral facial paralysis and guide the design of neural interfaces for facial reanimation. OBJECTIVE: To determine the detection threshold of side-to-side facial movement timing asymmetry and measure its effect on perceived movement naturalness. DESIGN, SETTING, AND PARTICIPANTS: Videos of 5 symmetrical facial movements (eye blink, rapid eyebrow raising, slow eyebrow raising, smiling, and lip depression) were edited to introduce 6 levels of side-to-side timing asymmetry, ranging from 33 to 267 milliseconds. Participants (N = 58) viewed video clips through an online survey service, indicating whether they noticed side-to-side asymmetry and judging movement naturalness on a 5-point scale. RESULTS: There was a significant difference among facial movements in asymmetry detection threshold. There was a strong correlation between naturalness ratings and amount of delay across movements (R = 0.823), with greater asymmetry being judged as progressively less natural. Blink was judged as less natural at 33, 67, 100, and 133 milliseconds of side-to-side delay compared with all other movements (P < .005). CONCLUSIONS AND RELEVANCE: Side-to-side asymmetry in blink timing is detected sooner and viewed as less natural compared with asymmetry of the eyebrow and lips. At 100 milliseconds of delay, nearly all movements are detected as asymmetric, although blink is judged as the least natural. These findings will help set timing goals for facial pacing technologies treating unilateral paralysis. LEVEL OF EVIDENCE: NA.