Asian Journal of Bio-Medical Research E-ISSN: 2454-6275
Original Article
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Morphometry in Relation to Stereoscopic Vision in Humans, An Osteology-Based study in an Iraqi Population of Middle-Eastern Arabic Ethnicity Dr. Ahmed Al-Imam1,2 Doctoral student (Medicine), School of Life and Medical Sciences- University of Hertfordshire, United Kingdom. Lecturer and Researcher, Faculty of Medicine, University of Baghdad, Iraq.
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Submission: 07-04-2016 Address for Correspondence: Dr. Ahmed M. Lutfi, House 18/5, Al-Akhtal Street, District 318, Al-Adhamyia, 10053, Baghdad, IRAQ. Tel: +964(0)7714338199; E-mail:
[email protected]
URN: http://pmindexing.com/ journals/index.php/AJBR/issue/ view/urn:pmi:jr:0019ajbr.v2i2.10071 How to Cite this Article: AlImam, Ahmed Mohammed Lutfi. Morphometry in Relation to Stereoscopic Vision in Humans, An Osteology-Based study in an Iraqi Population of Middle-Eastern Arabic Ethnicity. Asian Journal of BioMedical Research (ISSN:2454-6275), [S.l.], v. 2, n. 2, apr. 2016. ISSN 2454-6275. Available at: . Date accessed: 25 May. 2016.
Revision: 08-05-2016
Publication: 15-06-2016
ABSTRACT Introduction: In primates, the phenomenon of stereoscopic vision, also known as stereopsis, is far more advanced than in other mammals. Stereopsis is not only determined by the overlapping visual fields of both eyes. Neural mechanisms are also involved, both central and peripheral. A paper, published in 2013, discussed the monocular-based stereopsis. Past literature papers, focused mainly on measuring the inter-pupillary distance, as an indicator stereopsis. Materials and Methods: This research utilized 20 dry skull specimens of deceased adult Iraqis of Middle-Eastern Arabic ethnicity, to derive two morphometric representative parameters of the interocular distance. The parameters are the paramedian position of the Zygomatico-Frontal suture, and the nasal bridge width. Measurements were done using a standard Vernier. Statistics were calculated using SPSS 20. Results: The mean value for the inter-sutural distance was 101.556 millimeters, while the Variance and the Standard deviation were 28.804 and 5.366 respectively. The 95% confidence interval (95% CI) was in the range of 99.044 to 104.067. Concerning the nasal bridge width, the mean value was 25.192 millimeters, while the Variance and the Standard deviation were 5.389 and 2.321 respectively. The 95% CI was in the range of 24.105 to 26.278. Pearson’s correlation coefficient (r), for the two parameters, was 0.571, and the p-value was 0.0085. Conclusion: There was positive linear correlation between the paramedian position of the Zygomatico-Frontal suture and the nasal bridge width. Data from this paper, can be effectively exploited in Anthropology, evolutionary Biology, biometrics, and optical technologies including stereoscopic displays and stereographic cameras. Key words: Stereopsis; Zygomatico-frontal; Nasion; Inter-Sutural; Morphometry; Homo sapiens, Arab.
Introduction In primates, including Homo sapiens (the extant human), both eyes point forward and are a few centimeters apart. The task of extracting depth from two slightly dissimilar two-dimensional retinal images is dependent on the central nervous system (CNS). The mechanism is highly effective that an observer may detect, a depth difference of as small as 10 micrometers at a distance of 25 centimeters. Psychophysical and neurophysiological studies have begun to unravel the neural circuits in the brain which process the retinal signals to yield stereoscopic information.1 With exception of mammals, nearly all optic nerve fibers decussate at the level of the optic chiasma and enter the opposite side of the brain, to the visual (striate) cortex. As a derived condition in primates, the eyes are directed forward, and only the nasal fibers of the retina decussate in the optic chiasma.2 Asian Journal of Bio-Medical Research | Apr-Jun 2016 | Vol 2 | Issue 2
Viewing a real scene with both eyes (binocular), produces a more compelling three-dimensional experience of immersive space and tangible solid objects, compared to a monocular vision. Further, binocular information should provide advantages, concerning the planning and execution of natural reaching and grasping actions of a visually-detected subject.3 However, Humans can perceive depth even when viewing with one eye, and when viewing a two-dimensional picture of a three-dimensional scene. Therefore, the qualitative visual phenomenon of stereopsis, also known as stereoscopic vision, is not merely aby-product of binocular vision.4 Our two eyes are spatially separated (i.e. an interocular distance intervenes between both eyes), and the two visual fields contain both mismatched and matched optical data, known as binocular disparity and binocular concordance respectively. Each or both, of binocular 1
Ahmed Al-Imam: Morphometry in Relation to Stereoscopic Vision in Humans
disparity and binocular concordance, might contribute to a binocular advantage. Johansson (1973) found no binocular advantage for subjects judging distances up to about two meters when head motion was allowed. Thus, the binocular advantage thought to be provided by stereopsis may occur only in a highly constrained situation.When the head is still, the optic arrays at the two eyes are static, and there is inadequate information for stereopsis. However, the visual system apparently can obtain information from the disparity betweenthe unchanging optic arrays if necessary, as well as obtaining information from the continually changing optic flow field at each eye.5 Kinematic analyses revealed that prehensile movements made under monocular viewing differed substantially from those performed under binocular viewing. Grasping movements made under monocular viewing, showed longer movement times, lower peak velocities, proportionately longer deceleration phases, and smaller grip apertures. In short, there seems to an underestimation of the distance of objects. Furthermore, binocular vision contributes to prehension by providing additionalcues to the CNS.6,7 The use of stereoscopic (binocular) projections was proven to result in a 10-fold reduction in mean alignment error ascompared to the use of mono cular projections.8 Although average physiological interocular distance is 63 millimeters, it was found that any interocular distance of greater than 30 millimeters, was adequate to provide a user with maximal performance in depth perception.8 In this paper, the distance between the right and left Zygomatico-frontal suture (the inter-sutural distance) and the width of the nasal bridge, in dry skull specimens, will be used as morphometric deterministic parameters forthe interocular distance, and hence a representative parameter of stereopsis. Past literature papers, including Mead’s paper (1943) and other papers, relied mainly on using the inter-pupillary distance as a determinant of stereopsis.9 Further, the same morphometric determinants of stereopsis, can be used as biometric parameters in biomedical and technological applications. Over the last 20 years, several different techniques have been proposed for computer recognition of human faces, using a set of geometrical features, such as nose width and length, mouth position, and chin shape.10 The morphometric data can be utilized as a biometric value for facial recognition softwares.In a similar sense, these data can be used in optical applications including stereoscopic displays, and stereographic cameras. Such displays can improve the spatial understanding of a three-dimensional scenes or objects, improve memory/recall of scenes or objects, and improve learning of spatial relationships and environments.11
belong to 20 adult deceased members of the Iraqi population of Middle-Eastern Arabic ethnicity, of unidentified gender. The age ranged from 22 yearsto 51 years, with a mean value of 33.25 years. Measurement were taken at the Anatomical specimens’ unit at the laboratories of the department of Anatomy and Cellular Biology, at the faculty of Medicine, University of Baghdad. A standard stainless steel electronic Vernier micrometer gauge tool (UPC number 814870023454), was used to measure both the inter-sutural distance and the nasal bridge depth, in millimeters (mm), and the measurements were approximated to the nearest percentile of a millimeter. Each measurement was taken, while the skull specimen was fixed on a stable solid surface, and in parallel to the ground. The base of the posterior cranial fossa was in contact with a platform surface, via three contact points, the two mastoid processes and the external occipital protuberance, while the lower jaw (the mandible) projected freely (floated) downward. The Vernier was hold horizontally, by mean of a fixed stand and in parallel to the ground, thereby avoiding any tilting that may result in faulty Vernier’s readings. The measurement was taken exactly from the right to the left suture line of the Zygomatico-frontal suture, and at the medial end of each suture line. The Vernier external jaws were applied laterally and embracing each of the right and left Zygomatico-frontal suture (Figure 1). Simi larly, the width of the nasal bridge was measured at the level of the Nasion, at which the Vernier external jaws were applied against the lateral walls of the bridge to a depth of 20 mm posterior to the level of the coronal plane of the Nasion. To preventhuman-made error(s) while measuring, two Anatomists recorded each reading for each skull, and when their measurements were different to the nearest 1/10th of a millimeter, a 3rd reading was taken to resolve the measurement disparity. A fourth measurement was also taken, using an analogue Vernier, to confirm the accuracy of the electronic Vernier to the nearest millimeter. The final readings, in Table 1, represent the average readings for each skull, as recorded accurately using the electronic Vernier. Statistical data were calculated using the Statistical Package for Social Sciences (SPSS version 20.0), and Shodor-Interactivate software.14
Cameron et al. (2011), in their invention patency a “Stereo camera with automatic control of interocular distance”, used an automated control mechanism for the inter-ocular distance of two cameras to create 3D image-projections. Three dimensional imaging, also known as stereographic imaging, dates as far back as 1838. Stereographic cameras commonly include two lenses spaced laterally apart at a similar distance to the human’s average interocular distance, at approximately 65 mm. The effective distance of the lenses from each other is known as the interocular distance, (equivalent to that of humans. The interocular distance has a strong effect on the apparent depth of a stereographic image.12
Materials and Methods Materials used included 20 dry skull specimens, and two types of Vernier as a tool of morphometric measurement. The skull specimens
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Figure 1: Left-lateral view of the Human skull, the Zygomatico-frontal suture (right red circle) is located between the frontal process of zygomatic bone, and the zygomatic process of frontal bone. The Nasion (left red circle) is an anatomical point of articulation between the frontal bone and the two nasal bones.13
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Ahmed Al-Imam: Morphometry in Relation to Stereoscopic Vision in Humans
Results Datatabulation and statistical analyses (Table 1 and 2 respectively) were tabulated for the representative sample. The mean valuefor the inter-sutural distance was 101.5565millimeters, while the Variance and the Standard deviation were 28.804 and 5.366 respectively. The 95% confidence interval (95% CI) was in the range of 99.044 to 104.067 millimeters. Concerning the nasal bridge width, the mean value was 25.192 millimeters, while the Variance and the Standard deviation were 5.389 and 2.321 respectively. The 95% CI was in the range of 24.105 to 26.278. The Correlation coefficient (r), for the two parameters, was 0.571, and the P-Value was 0.0085, which is signi ficant at p < 0.05. A scattered plot and a linear regression graph, are visualized in Figure 2 and 3. The two calculated parameters, can be potentially used in some biomedical applications. These applications are not limited to bio metrics technologies, including facial recognition softwares, Further, it can be deployed in optical-technology applications including stereoscopic displays, stereographic cameras. Additional studies, with larger sample size are required, to prove or disprove the existence of a linear regression/correlation relationship with other stereopsis-deterministic parameters. These parameters, include but are not limited to, the interocular distance, interpupillary distance, the paramedian position of the optic disc and the optic canal, and the mid-point palpebral fissure distance from a midline point on the sagittal plane.
Discussion In Homo sapiens and other primates, binocular vision is far more advanced than other members of the class Mammalia. This is partially attributed to the overlapping (convergent) visual fields of the right and left eye, the neural decussation of retinal fibers (contained in the optic nerve) at the level of the optic chiasma, and other central neural mechanisms. Accordingly, the interocular distance between the right and left eye, is a co-determinant of the phenomenon of
Table 1. Stereopsis parameters of interest, with mean value for each parameter. Specimen Number
Age (years)
Inter-Sutural Distance (mm)
Nasal Bridge (mm)
1
22
96.72
22.91
2
41
96.43
22.53
3
32
103.37
22.23
4
33
98.49
24.94
5
25
96.45
22.85
6
31
102.23
25.63
7
33
111.36
26.45
8
47
113.43
26.06
9
34
97.84
24.87
10
26
97.36
22.19
11
41
100.86
28.48
12
32
91.15
22.51
13
25
103.60
29.11
14
32
103.02
27.20
15
29
102.89
27.08
16
48
101.90
26.90
17
30
108.47
25.98
18
31
101.50
25.96
19
22
98.52
21.90
20
51
105.54
28.06
101.5565
25.192
Mean Value
33.25
Figure 3: Graphical presentation of Linear Regression, for inter-sutural distance (x coordinate) versus the width of nasal bridge (y coordinate), the Slope valueis 0.247.
Figure 2: Scattered Plot, of inter-sutural distance versus the width of nasal bridge.
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stereopsis. Stereopsis is of high value in the 3D-visualization of an object, depth perception, enhancement of visuo-spatial and manual skills, and objects’ prehension based on a continuous feed visual stereoscopic data.
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Ahmed Al-Imam: Morphometry in Relation to Stereoscopic Vision in Humans
Table 2: Statistical analysis of deterministic parameters of stereoscopic vision (stereopsis). Statistical Parameters
Inter-Sutural Distance (x)
Width of Nasal Bridge (y)
Sample size*
20
20
Mean
101.5565
25.192
Median
101.7
25.795
Mode
None
None
Lowest value
91.15
21.90
Highest value
113.43
29.11
Range
22.28
7.21
Interquartile range
6.0625
4.425
First quartile
97.48
22.61
Third quartile
103.5425
27.035
Variance (s2)
28.804687105266
5.3895431578948
Standard deviation (s)
5.366999823483
2.3215389632515
Quartile deviation
3.03125
2.2125
Mean absolute deviation (MAD)
4.0245
1.9798
90%
99.48088 to 103.63112
24.29439 to 26.08961
95%
99.04417 to 104.06783
24.10549 to 26.27851
99%
98.12261 to 104.98939
23.70686 to 26.67714
Confidence Interval (CI)**
Statistical Correlation
Sample size: 20 Correlation coefficient (r): 0.57139057846809 The P-Value is 0.008507. The result is significant at p < 0.05
Linear Regression
Sample size: 20 Mean x (x): 101.5565 Mean y (y): 25.192 Intercept (a): 0.091336809666306 Slope (b): 0.24715959284077
*Adults of unidentified gender, from the Arabic Middle-Eastern ethnicity in Iraq. **The 95% CI was considered for statistical analyses in this paper.
Past literature papers, widely adopted the use of the interocular and interpupillary distance, as a morphometric representative/determinant of stereoscopic vision. In this paper, using dry 20 skull specimens of deceased Iraqi people of the Arabic ethnicity, the paramedian position of the right and left Zygomatico-frontal suture apart from each other (i.e. the inter-sutural distance) and the width of the nasal bridge, are used as two of stereopsis-deterministic parameters.
•• Miss Nada Monshid, for her help to provide the dry skull specimens for this study. Ms. Nada is an employee at the Anatomical specimen’s laboratory at the department of Anatomy and Cellular Biology, faculty of Medicine, University of Baghdad.
The 95% CI for the inter-sutural distance and the nasal bridge width, were 99.04417 to 104.06783 and 24.10549 to 26.27851 respectively. The Correlation coefficient (r) was 0.571, and the P-Value was 0.0085. An important potential application of this paper, is to use these two parameters as new morphometric representative parameters in biometrics, anthropology, comparative Anatomy and evolutionary biology, biometric application, facial recognition softwares, stereoscopic displays, and stereographic cameras.
1. Westheimer G. The Ferrier Lecture, 1992. Seeing depth with two eyes: stereopsis. Proceedings of the Royal Society of London B: Biological Sciences. 1994 Aug 22;257(1349):205-214. 2. Kent GG and Carr RK. Comparative Anatomy of the Vertebrates. McGrawHill Science Engineering; 2001. 3. Melmoth DR and Grant S. Advantages of binocular vision for the control of reaching and grasping. Experimental Brain Research 2006;171(3):371388. 4. Vishwanath D and Hibbard PB. Seeing in 3-D with just one eye stereopsis without binocular vision. Psychological Science 2013; Jul 26:0956797613477867. 5. Jones RK and Lee DN. Why two eyes are better than one: the two views of binocular vision. Journal of Experimental Psychology: Human Perception and Performance 1981;7(1):30. 6. Servos P, Goodale MA and Jakobson LS. The role of binocular vision in prehension: a kinematic analysis. Vision research 1992;32(8):15131521. 7. Loftus A, Servos P, Goodale MA, Mendarozqueta N and Mon-Williams M. When two eyes are better than one in prehension: monocular viewing and end-point variance. Experimental Brain Research 2004;158(3):317327. 8. Rosenberg LB. The effect of interocular distance upon operator performance using stereoscopic displays to perform virtual depth tasks. In Virtual Reality Annual International Symposium, 1993., 1993 IEEE 1993 Sep 18 (pp. 27-32). IEEE.
Future studies, with larger sample size of each gender, are required to further confirm the presence of a linear regression or a correlation relationship, between other various parameters of the interocular distance. These include, but are not limited to, paramedian position of the optic canal and the optic disc, and the lateral position of the midpoint of the palpebral fissure. Additionally, correlation of data attained from osteology researches and those done on live objects, are to be compared.
Acknowledgements Appreciation and gratitude to: 4
References
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Ahmed Al-Imam: Morphometry in Relation to Stereoscopic Vision in Humans
9. Mead LC. The influence of size of test stimuli, interpupillary distance, and age on stereoscopic depth perception. Journal of Experimental Psychology 1943;33(2):148. 10. Brunelli R and Poggio T. Face recognition: Features versus templates. IEEE Transactions on Pattern Analysis & Machine Intelligence 1993; (10):1042-1052. 11. McIntire JP, Havig PR and Geiselman EE. What is 3D good for? A review of human performance on stereoscopic 3D displays. In SPIE Defense, Security, and Sensing 2012 May 1 (pp. 83830X-83830X). International Society for Optics and Photonics. 12. Cameron J, Pace V, Campbell P and Allum RC, inventors. Stereo camera with automatic control of interocular distance. United States patent US 7,899,321. 2011 Mar 1.
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13. Henry Vandyke Carter-Henry Gray (1918) Anatomy of the Human Body (See “Book” section below) Bartleby.com: Gray’s Anatomy, Plate 164. 14. Available at: http://www.shodor.org/interactivate/activities/BoxPlot/. Accessed March 30, 2016.
Author Contribution: Ahmed Al-Imam is the sole author of this paper. He was res ponsible for the research concept and methodology, literature review, data collection and tabulation, collecting and handling specimens, visual presentation, and conducting statistical analysis. Source of Support: Nil. Conflict of Interest: None declared.
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