The Effect of View Angle of Stereoscopic image on Heterophoria
The Effect of View Angle of Stereoscopic image on
Heterophoria
2 Department ofGimcheon University,
Advanced Science and Technology Letters Vol.61 (Healthcare and Nursing 2014), pp.89-93 http://dx.doi.org/10.14257/astl.2014.61.22
The advent of 3D display technologies has brought a significant change in the imaging market and it has been considered as the next generation broadcasting technology. Despite of it, the 3D display technology has several issues including photoepileptic seizure, display motion sickness and visual fatigue, setting back the development of the 3D industry [1],[2]. ISO, an international organization for standardization, issued a few guidelines related with the image safety, and the guideline emphasizes safety issues including photoepileptic seizure, display motion sickness and visual fatigue [3]. Also, 3D consortium has suggested the detailed guideline in which recommended specifications for the display and LCD shutter glass are stated for preventing the visual fatigue [4]. In South Korea, the Korea Communication Commission organized the 3D safety commission and has operated starting from May 2010 for supporting studies on the 3D safety. An experimental study on five basic items of 3D viewing (viewing distance, watching period, viewing angle, distance between the pupils, and motion sickness sensitivity) was conducted in
Keywords: 2D images, 3D images, Phoria, Solid angle
Undergraduate students, attending one undergraduate school in Gumi-si, were participated in this study. Written consents were obtained prior to examination. All subjects were divided into two groups and they completed the horizontal heterophoria test before watching, after watching 2D and after watching 3D, and it was shown that the far distance horizontal heterophoria was increased in both groups as exophoria after watching 3D with the solid angle standards of 0.23 sr and 0.10 sr (p<0.05). Also, the subject group with the solid angle standards of 0.23 sr was shown to have an increase in the near distance horizontal heterophoria after watching 2D and watching 3D, and the subject group with the solid angle standards of 0.10 sr showed the similar increase in the near distance horizontal heterophoria after watching 3D. There was a significant difference in the relation between the angle of view for watching 3D and the horizontal heterophoria (p<0.05).
Abstract. The purpose of this study was to investigate the relationship between
heterophoria and angle of view upon watching 3D through the heterophoria test.1 kjh@ikw.ac.kr
730 Kangdongro Gumi City, Gyeongbuk 730-739, Repubric of Korea
Ji-hoon Kang
1 Department of Optometry & Vision Science, Kyungwoon University
1
, Jeong-sik Son
2
, Soo-chul Park
1, †
1 Introduction
Advanced Science and Technology Letters Vol.61 (Healthcare and Nursing 2014)
2010, and announced the clinical suggestion (Ver 1.0) for the 3D safety, which was made based on the literature investigation and opinions of the medical industry in December 2012 and the revised version (Ver. 3.0) in December 2012 [5]. In this study, the relationship between heterophoria and angle of view upon watching 3D in compliance with the 3DTV safety guideline through the heterophoria test. This study could be employed as reference for the preparation of the 3DTV guideline and of proper measures to be taken for any irregularities caused by watching 3D.
2 Research Methods
2.1 Research Methods
From December 2012 to April 2013, eighty students with the corrective vision of 0.8 or above, attending one undergraduate school in Gumi, Gyeongsangbuk-d and being able to watch 3D, completed the horizontal heterophoria test. All subjects were divided into two groups, except for 4 subjects who failed to pass the suppression test, and 40 subjects were assigned to the group A and 36 subjects to the group B. Subjects were required to watch 3D with the standard of a solid angle, and the solid angle is defined as the two-dimensional angle in three dimensional space that an object subtends at a point and its equation is (1). Upon categorization by solid angle, the group A is 0.23 sr and the group B is 0.10 sr.
The data analysis was made with SPSS ver. 20.0, and survey questionnaires and data collected before watching and after watching 2D and 3D were compared in graphs and tables by using the paired t-test, independent t-test and ANCOVA. ANCOVA handled a result of the visual performance inspection test before watching as covariate. When p<0.05, it was considered as statistically significant.
2 Solid angle = S/r [sr] (1)
.
Fig. 1 Process
Advanced Science and Technology Letters Vol.61 (Healthcare and Nursing 2014)
3 Result
3.1 Change in Far-Distance Horizontal Heterophoria after Watching 2D and 3D
The group watched with the solid angle of 0.23 sr was shown to have an increase in the far-distance horizontal heterophoria as exphoria after watching 2D (-2.36±2.50) than before watching (-2.21±2.11), but not significant. Also, there was a significant increase in the far-distance horizontal heterophoria as exphoria after watching 3D (- 2.74±2.64) than before watching 3D (-2.21±2.11) (p<0.05).
The group watched with the solid angle of 0.10 sr was shown to have a significant increase in the far-distance horizontal heterophoria as exphoria after watching 2D (- 1.55±0.85) than before watching 2D(-1.91±1.06)(p<0.05). Also, there was a significant increase in the far-distance horizontal heterophoria as exphoria after watching 3D (-1.55±0.85) than before watching 3D (-2.47±1.23) (p<0.05)(Table 1).
Table 1. Change in Far-Distance Horizontal Heterophoria after Watching 2D and 3D upon
Solid Angle
Before After watching 2D After watching 3D Solid angle watching
(sr) 1) 2) 3) 4)
M±SD M±SD p p M±SD p p 0.23 -2.21±2.11 -2.36±2.50 0.460 -2.74±2.64 0.023 0.267
0.90 0.10 -1.55±0.85 -1.91±1.06 0.005 -2.47±1.23 0.000 5) p
0.06 0.371 0.614
Unit : △(Prism)Phoria : + Esophoria , - Exophoria 1) 2) p : Paired t-test (Before watching : ANCOVA (Before watching 3) 4) – After watching 2D ) p – After watching 2D ) p : Paired t-test (Before watching : ANCOVA (Before watching 5) – After watching 3D ) p – After watching 3D ) p : Independent t-test
3.2 Change in Near-Distance Horizontal Heterophoria after Watching 2D and
3D
The group watched with the solid angle of 0.23 sr was shown to have a significant increase in the near-distance horizontal heterophoria as exphoria both after watching
2D (-7.03±4.77) and 3D(-7.94±4.89) than before watching (-6.43±4.52) (p<0.05).
The group watched with the solid angle of 0.10 sr was shown to have a significant increase in the near-distance horizontal heterophoria as exphoria after watching 3D (- 8.64±3.36) than before watching (-10.11±3.22)(p<0.05). Even through it was shown Advanced Science and Technology Letters Vol.61 (Healthcare and Nursing 2014)
that there was a significant increase in the near-distance horizontal heterophoria as
5)
exphoria by a solid angle (p =0.046), there was no significant change in a result of ANCOVA (Table 2).
Table 2. Change in Near-Distance Horizontal Heterophoria after Watching 2D and 3D upon
Solid Angle
Before After watching 2D After watching 3D Solid angle watching
(sr) 1) 2) 3) 4)
M±SD M±SD p p M±SD p p 0.23 -6.43±4.52 -7.03±4.77 0.001 -7.94±4.89 0.000 0.747 0.447 0.10 -8.64±3.36 -9.10±3.64 0.149 -10.11±3.22 0.004 5) p
0.06 0.066 0.046 Unit : △(Prism) Phoria : + Esophoria , - Exophoria 1) 2) p : Paired t-test (Before watching : ANCOVA (Before watching 3) 4) – After watching 2D ) p – After watching 2D ) p : Paired t-test (Before watching : ANCOVA (Before watching 5) – After watching 3D ) p – After watching 3D ) p : Independent t-test
4 Discussion and Conclusions
In this study, the group watched with the solid angle of 0.23 sr was shown to have an increase in the far-distance horizontal heterophoria as exphoria after watching 3D than before watching. The group watched with the solid angle of 0.10 sr was shown to have an increase in the far-distance horizontal heterophoria as exphoria after watching both 2D and 3D than before watching. It could be resulted by that a fusion stimulus might act as a fatigue factor more in watching 3D than in watching 2D In case of a change in the short distance horizontal heterophoria upon a solid angle after watching 2D, t-test showed it as an increase as exphoria after watching 2D, but ANCOVA did not verify it as an increase. Such difference between results of t-test and ANCOVA could be caused by that a change between before and after watching
3D, shown in ANCOVA, is caused by a difference in visual functions before watching 3D, but a difference between watching 2D and watching 3D, shown in t-test, is resulted by a solid angle.
This study could be used as reference for the preparation of the 3DTV guideline and of proper measures to be taken for any irregularities caused by watching 3D, and it would be assumed that the 3D safety guideline should be subject to consistent revision, which is based eon additional analysis of visual functions.
Advanced Science and Technology Letters Vol.61 (Healthcare and Nursing 2014) References
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