Role of depth in eye distance measurements: comparison of single and stereo-photogrammetry

3D-Analysis of Mouth, Nose and Eye Parameters in Children with Fetal Alcohol Syndrome (FAS)

Background: Fetal alcohol spectrum disorder (FASD) is a developmental disorder with severe negative lifetime consequences for the affected person. Numerous diagnostic methods for facial assessment in FAS exist, but most of them are based on subjective evaluations. Our aim was therefore to find objective methods for the verification of FAS(D). Methods: 58 children (28 FAS; 30 controls) were examined prospectively. 3D facial scans were performed for each child and facial parameters at the mouth, nose and eye regions were measured and compared between the groups. Results: Significant differences could be found for the distance between right and left sulcus nasi at the transition point to the philtrum (p < 0.001), for the inner canthal distance (p = 0.001) as well as for the right and left palpebral fissure length (p < 0.001). No significant difference between the FAS and control children could be found for the measurements of mouth breadth (p = 0.267) and breadth between the left and right alares nasi (p = 0.260). Conclusions: Measurements of mouth breadth and nose breadth for the alares nasi are not suitable for FAS diagnosis. In contrast, digital contactless measurements of the distance between the right and left sulcus nasi at the transition point to the philtrum, as well as the inner canthal distance and palpebral fissure length of the left and right eyes, showed significant differences when comparing children with FAS to healthy controls. These measurements could thus be additional objective means for the verification of FAS.

The 3D Facial Norms Database: Part 1. A Web-Based Craniofacial Anthropometric and Image Repository for the Clinical and Research Community

With the current widespread use of three-dimensional (3D) facial surface imaging in clinical and research environments, there is a growing demand for high-quality craniofacial norms based on 3D imaging technology. The principal goal of the 3D Facial Norms (3DFN) project was to create an interactive, Web-based repository of 3D facial images and measurements. Unlike other repositories, users can gain access to both summary-level statistics and individual-level data, including 3D facial landmark coordinates, 3D-derived anthropometric measurements, 3D facial surface images, and genotypes from every individual in the dataset. The 3DFN database currently consists of 2454 male and female participants ranging in age from 3 to 40 years. The subjects were recruited at four US sites and screened for a history of craniofacial conditions. The goal of this article is to introduce readers to the 3DFN repository by providing a general overview of the project, explaining the rationale behind the creation of the database, and describing the methods used to collect the data. Sex- and age-specific summary statistics (means and standard deviations) and growth curves for every anthropometric measurement in the 3DFN dataset are provided as a supplement available online. These summary statistics and growth curves can aid clinicians in the assessment of craniofacial dysmorphology.

A review of facial image analysis for delineation of the facial phenotype associated with fetal alcohol syndrome

The facial anomalies associated with fetal alcohol syndrome (FAS), some of which are also present in individuals with less severe forms of the broader category of fetal alcohol spectrum disorders (FASD), are typically identified with the aid of linear distance measurements taken between facial landmarks. Digital facial imaging methods are increasingly being used in syndrome delineation. Distance measurements derived from stereo-photogrammetry and facial surface imaging have been used to study the FAS facial anomalies. Geometric morphometric methods capture the spatial arrangement between landmarks, providing a statistical platform for comparison of facial shapes, and have been shown to hold promise for characterizing the FAS facial shape. We review the progression in the use of imaging and image analysis methods in studies on the facial phenotype associated with FAS.

Design, construction, and testing of a stereo-photogrammetric tool for the diagnosis of fetal alcohol syndrome in infants

Stereo-photogrammetry provides a low cost, easy to use, and noninvasive alternative to traditional facial anthropometry for the diagnosis of fetal alcohol syndrome (FAS). We describe such a system for use in obtaining 3-D facial information in infants. The infant is photographed using three high resolution digital cameras simultaneously while seated in a car seat. The subject's head is enclosed in a control frame during imaging. Technical system tests, namely control frame interpolation, camera calibration reliability, and camera synchronization delay assessments were performed. Direct and stereo-photogrammetric measurements of a doll were compared. Of 275 inter-landmark distances, 100% were within a 1.5 mm error range and 92.36% within a 1 mm error range when the two modalities were compared. Stereo-photogrammetry proved to be highly precise with submillimeter error in landmark placement for all landmarks on the doll. An intra-modality comparison of inter-landmark distances using two sets of images of five subjects showed the stereo-photogrammetric system to be highly reliable, with an average 72.25% of distances within a 1 mm error range. The system has potential for large scale screening and surveillance studies for FAS.

Eye measurements in 7-year-old black South African children

BACKGROUND

Ethnic variation often renders anthropometric reference values obtained in one population unsuitable for use in others. Fetal alcohol syndrome (FAS) diagnosis relies in part on the evaluation of certain anthropometric facial features. Measurements of these facial features in South African children have not been compared with measurements obtained in other populations.

AIM

The study seeks to determine the suitability of reference values obtained in other populations for the diagnosis of the facial phenotype associated with FAS in South African children.

PARTICIPANTS AND METHODS

Palpebral fissure length (PFL), interpupillary distance (IPD), inner canthal distance (ICD) and outer canthal distance (OCD) measured in a group of black South African children were obtained from digital photographs using stereophotogrammetry, and compared with measurements published for other populations. The study population comprised 17 7-year-old boys and 17 7-year-old girls. The precision and reliability of measurements were examined with reference to published data.

RESULTS

Eye distance measurements in the study population do not consistently reflect those in any one other population for which such measurements have been published.

CONCLUSION

Population-specific reference values of eye distance measurements should be established for South African children.

Morphometric analysis of facial landmark data to characterize the facial phenotype associated with fetal alcohol syndrome

Procrustes analysis and principal component analysis were applied to stereo-photogrammetrically obtained landmarks to compare the facial features associated with fetal alcohol syndrome (FAS) in subjects with FAS and normal controls. Two studies were performed; both compared facial landmark data of FAS and normal subjects, but they differed in the number of landmarks chosen. The first study compared landmarks representing palpebral fissure length, upper lip thinness and philtrum smoothness and revealed no significant difference in shape. The second study added to the landmarks used in the first those affected by mid-face hypoplasia, and revealed significant differences in shape between the two groups, broadly confirming the FAS gestalt reported in the literature. Some disagreement in the characteristic FAS facial shape between our results and those reported in the literature may be due to ethnic variation.

Stereo image matching for facial feature measurement to aid in fetal alcohol syndrome screening

The facial phenotype associated with fetal alcohol syndrome is identified through the measurement of facial distances and their comparison to population norms. As an alternative to time-consuming direct manual measurements, stereo photogrammetry has been used to obtain the required facial measurements from stereo digital photographs. While stereo photogrammetric measurement is faster, it requires manual marking of relevant facial landmarks on digital images. We present an algorithm that automatically finds matched feature points on the second of a pair of stereo images, after manual marking of the first. Standard image processing tools are used for preprocessing. Matching is based on a simple exhaustive search in an image window, with the sum of squared differences of the pixel intensities in the two images as the objective function. Eye measurements, namely palpebral fissure length, interpupillary distance, inner canthal distance and outer canthal distance, as well as distances that can be used to approximate the circularity of the upper lip, were obtained using the manual method of marking both images, and the method of automatic marking of the second image. Comparison revealed mean differences less than 1mm.

Measurements of the Periocular Facial Area with Web-Based Software

We developed a simple Web-based program to make measurements on displayed photographs between several ocular and periocular landmarks. The measurements were: (1) vertical distance between the margin of the upper and lower eyelids (palpebral aperture), (2) distance between the lower eyelid margin and the inferior corneal margin (palpebro-limbar distance); (3) interpupillary distance; (4) ocular proptosis. We measured the distances using the Web program and compared them with manual measurements on the subject's face. The measurements involved 102 eyes of 51 patients with a variety of ophthalmic conditions. There was good agreement between manual and computer measurements. For example, for manual measurements in 49 patients, we obtained interpupillary distances ranging from 45 to 69 mm (mean 61, SD 6), whereas for computer measurements we found values ranging from 42 to 49 mm (mean 59, SD 6). The mean of the differences between manual and computer measurements was -2.0 mm (SD 4.3) and the 95% limits of agreement were -6.5 to 10.5 mm. Thus, computer measurements tended to give a higher reading by between 0.8 and 3.2 mm (95% confidence interval for the difference). Web-based software may be used to perform measurements on two-dimensional pictures and the technique appears to be suitable for telemedical purposes.

Nasal dimensions in normal subjects: conventional anthropometry versus computerized anthropometry

The aim of the current investigation was to compare computerized measurements of nasal linear distances (nasal tip protrusion, height of the cutaneous upper lip, length of the nasal bridge) collected from 705 healthy individuals from Northern Italy (age range 6-60 years) using an electromagnetic digitizer with conventional anthropometric measurements: one set obtained on individuals of central European origin (Zankl et al.), and one set collected from North American Caucasians (Farkas et al.). On average, the present lengths of the nasal bridge were always significantly smaller than the European data (P < 0.01, Student's t for independent samples). Nevertheless, only in one sex and age group of 18 the discrepancy between the two mean values was larger than 10 mm. In other 10 groups, the mean values differed less than 5 mm. More limited differences (up to 6.5 mm) were found in comparison to the American data. For nasal tip protrusion, digital and conventional data were significantly different (up to 4 mm) in 18 instances of 30. On average, the present heights of the cutaneous upper lip were always smaller than the European data (up to 2.9 mm). The differences were statistically significant in 14 groups of 18. Minor discrepancies (less than 1 mm in nine groups of 12) were found in comparison to the American data. Statistical significance was reached only in seven comparisons. In conclusion, the conventional anthropometric and the digital data compared in the current study, though not superimposable, seemed sufficiently interchangeable, at least from a clinical point of view.

Image processing for craniofacial landmark identification and measurement: a review of photogrammetry and cephalometry

Facial surface anthropometry and cephalometry have been used for many years for the diagnosis of malformations, surgical planning and evaluation, and growth studies. These disciplines rely on the identification of craniofacial landmarks. Methods for 3D reconstruction of landmarks have been introduced, as have image processing algorithms for the automation of landmark extraction. This paper reviews facial surface anthropometry and cephalometry with reference to the image processing algorithms that have been applied and their effectiveness.

Three-dimensional point localisation in low-dose X-ray images using stereo-photogrammetry

A stereo-photogrammetric method for three-dimensional reconstruction of points in low-dose digital X-ray images obtained using a scanner with similar imaging geometry to that of computed tomography scan projection radiography, was analysed. A calibration frame containing 25 radio-opaque markers with known three-dimensional locations was scanned, and the accuracy of reconstruction of the marker positions under varying control point configurations and separation angles was assessed. Errors of less than 1 mm were obtained when nine test points were reconstructed, with 16, 11 and 7 control points at a 90 degrees separation angle, and with 16 and 11 control points at 75 degrees and 60 degrees separation angles. The optimum reconstruction, with a resultant error of 0.68 mm, was found to occur at a separation angle of 90 degrees, with the largest number of control points (16) used to calculate the parameters of the transformation. Extrapolation in the scanning direction beyond the space defined by the control points gave errors of less than 2 mm. This method should be suitable for three-dimensional point reconstruction in applications such as cephalometry, brachytherapy planning and assessment of spinal shape.