Hindawi Journal of Ophthalmology Volume 2019, Article ID 1570309, 9 pages https://doi.org/10.1155/2019/1570309 Research Article Screening for Stereopsis of Children Using an Autostereoscopic Smartphone Yanhui Yang1 and Huang Wu 2 1Department of Pediatrics, Second Hospital of Jilin University, Changchun, China 2Department of Optometry, Second Hospital of Jilin University, Changchun, China Correspondence should be addressed to Huang Wu; [email protected] Received 29 March 2019; Accepted 30 September 2019; Published 31 October 2019 Academic Editor: Antonio Benito Copyright © 2019 Yanhui Yang and Huang Wu. *is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. *e advantage of using an autostereoscopic smartphone is that it can achieve 3D effects without the need for glasses. *e purpose of this study was to evaluate whether this technology could be utilized to detect stereoacuity. Methods. An autostereoscopic smartphone was used to imitate Lang stereotest I & II, Pass Test 3, Dinosaur Stereoacuity Test, and the Random Dot Stereo Acuity Test to screen the stereopsis of children from 3–6 years old. Results. No significant difference was found between each pair of groups (autostereoscopic smartphone vs. Lang stereotest I, Lang stereotest II, Pass Test 3, Dinosaur Stereoacuity Test, and Random Dot Stereo Acuity Test, respectively; Wilcoxon signed-rank test, P value all >0.05). All of the weighted kappa were higher than 0.84. *erefore, all of the comparisons between measurements showed a high level of agreement. Conclusions. *e autostereoscopic smartphone is an effective tool when used for the screening of deficiency in stereopsis. 1. Background dimension (2D) picture into a 3D image without the aid of glasses. *e essential aim of those methods was to transfer a Stereopsis is a kind of function by which subtle differences in 2D picture to one eye while transferring another 2D picture to distance can be judged precisely while stereoacuity is an another eye and then the predesigned disparities between the index used to evaluate stereopsis. *e principle for evalu- two 2D pictures would help to express a 3D image. Parallax ating the threshold of stereoacuity is based on the minimum barrier technology and lenticular technology are two mature disparity that one can detect. Sometimes, testing is carried techniques. *e former contains vertical apertures to cover out in a real-life situation, such as in the Howard‒Dolman the light at certain angles to ensure sending different images to test [1], which is seldom used clinically nowadays, or the different eyes, while the latter uses the refraction function of Frisby stereotest [2–4]. However, separating the two eyes is microlenses to deviate the light to certain directions to dif- essential when testing for the threshold of disparity which is ferent eyes [13]. However, some defects, e.g., the lower image most commonly used in the clinical setting. Red- and green- resolution, reduced brightness, small viewing angles, and colored spectacles are used in the TNO test [5–7], while crosstalk, limited the application of the traditional method. polarized glasses are used in the Titmus test [8–10]. Com- Novel technologies have been created to address this problem, puter-based testing is another powerful tool currently used such as the use of the sub-pixel-level tunable lenticular liquid for testing stereopsis, with polarized 3-dimensional (3D) crystal (LC) lens array to obtain the same resolution as a 2D- technology [11] or 3D shutter glasses technology [12]. display panel [17] or multidirectional backlight to provide a *e development of naked-eye 3D technology has very efficient display [18]. accelerated recently in the fields of advertising and enter- Fujikado et al. [23] evaluated the stereopsis of strabismus tainment, with its obvious advantage that glasses are no longer patients using three-dimensional images displayed on a 10- required [13–22]. Several techniques are used to turn a two- inch LC display (resolution 640 × 480 pixels) equipped with 2 Journal of Ophthalmology RLLLLRR RR L LCD panel Parallax barrier LCD panel Right eye Left eye Parallax barrier Left eye Right eye (a) (b) Figure 1: Diagram for parallax barrier autostereoscopic display. (a) Top-down view of eyes viewing. (b) 3D angle of viewing. Parallax barriers can send the right column to the right eye and the left column to the left eye, which means that what the right eye sees cannot be seen by the left eye and vice versa. *us, binocular vision would be achieved when adding appropriate disparity elements between the two images. an image-splitter system in almost 20 years ago. Breyer et al. [24] established a random-dot stereotest based on the use of an autostereoscopic monitor, and achieved a high correla- tion with the Lang stereotest I in children. However, the relatively low screen resolution of autostereoscopic tests renders these tests more useful as qualitative tools than precise quantitative tools. *e situation has been improved by the development of high-resolution smartphones with naked eye 3D technology. For a common naked eye 3D glasses-free mobile phone (e.g., ivvi K5 mobile phone [ivvi Scientific, NanChang, Co., Ltd. China]) equipped with a 5.5 inch IPS screen, the resolution Figure 2: Photograph of the actual testing. of the display is 1920 ×1080 pixels. Parallax barrier tech- nology was adopted to produce a 3D effect. *e principle of the technology is schematically shown in Figure 1. *e were enrolled, comprising 30 boys and 21 girls, aged 3–6 display density of the screen is 401 PPI (pixels per inch). At a (4.6 ± 1.0) years. Before participation in the study, informed checking distance of 40 cm, a pixel disparity equal to 33 consent was obtained from the guardian for all underage seconds of arc (arcsec). Limited by the principle of parallax participants. *e research protocol followed the tenets of the barrier technology (Figure 1), the minimum disparity would Declaration of Helsinki and was approved by the ethics be twice of the physical pixels of the screen. *erefore, the committee of the Second Hospital of Jilin University (No. test threshold was 66″ at 40 cm. When the distance was 2017–89). prolonged to 65 cm, the test threshold would approach 40″. However, the stereopsis threshold value may not be precise enough to measure a people’s stereoacuity, it is usable to be a 2.2. Smartphone and Comparison Tests. Naked eye 3D screen tool. For example, the threshold of Lang stereotest I & glasses-free original ivvi K5 mobile phone (display resolu- II (Lang-Stereotest AG, Kusnacht, Switzerland) is 550″ and tion: 1920 ×1080 pixels, display density: 401PPI) was used as 200″, respectively; the threshold of PASS Test 3 (Vision a stereopsis evaluation tool. Actual test picture is shown in Assessment Corporation, Illinois, USA) and Dinosaur Figure 2. Five stereotests, Lang stereotest I & II, PASS Test 3, Stereoacuity Test (Bernell, a Division of Vision Training Dinosaur Stereoacuity Test and Random-Dot Stereo Acuity Products, inc. Indiana, USA) is 60″ and 40″, respectively. Test (Vision Assessment Corporation, Illinois, USA), were We were interested in investigating the effect of this chosen as Screening Stereo tests. technology utilized to detect stereoacuity with a portable autostereoscopic smartphone, utilizing its flexibility with the 2.3. Test Targets Design and Test Methods aim of obviating the need for the wearing of glasses. 2.3.1. Imitating Lang Stereotest I & II. A program written in 2. Methods C# was used to produce random-dot test targets (Figure 3). *e test method was the same as the test procedure as 2.1. Subjects. *e study was conducted at the Second standard Lang stereotest. *e test distance was 40 cm. *e Hospital of Jilin University in China. A total of 51 children disparity of the cat, star, and car in Lang stereotest I was 36 Journal of Ophthalmology 3 (a) (b) (c) Figure 3: Imitating Lang stereotest I. (a) *e picture viewed by the left eye. (b) *e picture viewed by the right eye. (c) Simulation of the percepts generated by the test images. *e pattern of cat, star, and car appear to pop out of the background plane. *e disparity of the cat, star, and car was 36 pixels (equivalent to 1200″), 18 pixels (equivalent to 600″), and 16 pixels (equivalent to 550″), respectively. pixels (equivalent to 1200″ at 40 cm, similarly hereinafter), During the test procedure, the head of the subject should not 18 pixels (600″), and 16 pixels (550″) (Figure 3). *e dis- swap. *e smile face may come out of the plane (crossed parities of the elephant, truck, moon, and star in Lang disparity) or go inside the plane (uncrossed disparity). stereotest II were 18 pixels (600″), 12 pixels (400″), 6 pixels (200″), and 6 pixels (200″), respectively. 2.3.3. Imitating Dinosaur Stereoacuity Test. Imitating part 2 of the Dinosaur Stereoacuity Test, which including 400″, 2.3.2. Imitating Pass Test 3. A scanner (ScanMaker S260, 200″, and 80″. *e animal may stand out of the plane Microtek International, Inc. Shanghai, China) was used to (crossed disparity) or dent into the plane (uncrossed dis- scan the card. A polarizer film was covered on the surface of parity) (Figure 5). *e test distance was 40 cm, at which 12 the card when scanning, while the position should be aligned pixels and 6 pixels disparities were equivalent to 400″ and with the polarization direction of the drawing. After two 200″, respectively. When the distance was changed to 33 cm, scanning with the help of polarizer film, a blur picture would 2 pixels were equivalent to 80″. be decomposed into two clear pictures (Figure 4).