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In this paper, we present a novel automated method for assessing visual acuity in infants and toddlers by using an eye-tracking system.
Visual acuity measurement is an important visual function test to perform in infancy and childhood. However, accurate visual acuity measurement in infants is difficult because of deficiencies in their communication ability. This paper presents a novel automated method to assess visual acuity in children (5-36 months old). This method, the automated acuity card procedure (AACP), uses a webcam for eye tracking and recognizes children's watching behaviors automatically. A two-choice preferential-looking test is performed when the tested child watches the visual stimuli shown on a high-resolution digital display screen. When the tested child watches the stimuli, their facial pictures are recorded by the webcam. These pictures are used by the set computer program to analyze their watching behavior. With this procedure, the child's eye movement responses to different stimuli are measured, and their visual acuity is assessed without communication. By comparing the results with grating acuity obtained by Teller Acuity Cards (TACs), AACP performance is deemed comparable to that of TACs.
The infantile period is a critical period for visual development. Visual problems that arise early in life can have a significant impact on a child's development. It is important to be able to perform a quantitative visual assessment in infants, which can help detect early vision problems. However, because infants are not cognitively developed or expressive enough to recognize visual acuity chart symbols, such as letters or graphs, measuring their visual acuity is difficult. The current gold standard for infant vision assessment is the acuity card procedure1 based on the preferential looking test2. However, because this method requires experienced testers to judge visual acuity by observing the child's eye movements3,4,5,6, it is limited by the experience of the testers4,5. Therefore, acuity card procedures, such as Teller Acuity Cards (TACs)5,6, remain a subjective method. Thus, there is a need for a method that can quantitatively measure visual acuity in infants and young children, that can be used without the need for verbal communication and that is not limited by requiring experienced testers.
The invention and use of the remote eye tracker enabled an automated acuity measuring system to be developed. In previous studies, eye-tracking methods have been used as a tool for visual function evaluation in children7,8,9,10. A remote eye tracker can be used for gaze tracking and is a substitute for a tester's observation of a child's eye movements. The ACTIVE procedure7 and AVAT procedure10 are fully automated visual acuity tests with a remote eye tracker; they have yielded comparable visual acuity results to the Keeler Acuity Cards test in healthy infants and young children. As opposed to other recent studies, we used a webcam instead of a remote eye tracker to capture the child's gaze. We invented an eye movement data automatic acquisition method based on computer vision. The procedure combined the eye movement acquisition method with the preferential looking technique in assessing visual function in children.
This paper aims to present a novel automated method, which can evaluate visual acuity in young children, called the automated acuity card procedure (AACP). This procedure is particularly useful for infants and younger children who have not yet acquired sufficient communication skills. The key aspect is that visual responses can be quantitated to yield grating acuity in infants and young children. Grating acuity measurement enables the detection of visual pathologies and plays an important role in subsequent medical management.
The protocol described here was approved by the Ethical Committee of Peking University First Hospital (PKUFH 2018-223). The procedures adhered to the tenets of the Declaration of Helsinki for research involving human subjects. The study format was described, and informed consent was obtained from the parents of the participants.
1. Preparation of the apparatus
NOTE: The AACP components were set up in a mildly illuminated test room. Drapes were pulled in the room to avoid interference from sunlight. A display system, a recording system, and an analysis system were the three components of the AACP (Figure 1).
2. Eye-tracking calibration
3. Testing procedure
The AACP was applied to one group of children11: 155 normally developing infants and toddlers (5 to 36 months old, based on gestational age). In a previously published study, the grating acuity results obtained by the AACP were compared with those obtained by TACII. The results obtained by these two procedures are significantly correlated (r153 = 0.83, p < 0.001). Only 10.32% (16 of 155) of the children's results differed by more than one octave. Among them, eight child...
Several studies7,8,9,10 based on the eye-tracking method have shown the value of this method in evaluating infants and young children who have difficulty in verbal communication. However, the number of participants in previous studies is relatively small. Only 30 infants under 12 months of age were tested by the ACTIVE procedure, which was developed by Jones et al.7. The...
The authors have made the following disclosures: BK.Y., XQ.L., JS.C., and L.W.: China National Invention Patent "A method and system for face detection and pupil localization in continuous video frames" (CN201910865074.4); XQ.L., BK.Y., JS.C., and L.W.: China National Invention Patent "Vision automatic testing system" (No. 201510919621.4).
This study was supported by Capital's Fund for Health Improvement and Research (No. 2018-2Z-4076) and Peking University First Hospital SEED Research Funds (2019SF31).
Name | Company | Catalog Number | Comments |
AACP procedure software | In-house | In-house | The AACP procedure software (China National Invention Patents, No. 201910865074.4 and No. 201510919621.4) comprises a stimulus displaying module, a vision testing module, and a testing result processing module. |
Computer processor | Intel Corporation, Santa Clara, CA, USA | Intel CORE i7-6500U processor | Analysis system |
Display monitor | InnoLux Co., Ltd., China | InnoLux M280DGJ-L30 | Display system |
Webcam | Logitech International S.A., Lausanne, Switzerland | Logitech C920 high-definition pro webcam | Recording system |
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