AsianScientist (Dec. 19, 2017) – Scientists in China have demonstrated that augmented reality can be used to correct amblyopia, also known as ‘lazy eye’. Their findings are published in Psychological Science.
When signals between the brain and one eye go awry, input from the other eye can become dominant, resulting in ‘lazy eye.’ The condition is common and is typically treated by forcing the less dominant eye to adapt, either through lab-based training or using an eyepatch.
In the present study, a research group led by Professor Bao Min at the Chinese Academy of Sciences found that people may be able to use wearable augmented-reality technology to reduce visual discrepancy as they go about their everyday activities.
“With this altered-reality system, participants interact with the natural world that is changed through real-time image processing. The system delivers altered but complementary video to each eye in real time, forcing participants to make use of the visual inputs to both eyes cooperatively,” said Bao.
The altered-reality system can be considered as a special type of the augmented-reality technology, in which some aspects of the scene are altered before the video is delivered to the observer, but no unnatural and nonexistent object (e.g. an arrow or a web page) is superimposed. Using augmented reality to alter visual input in this way avoids some limitations of lab-based training.
In their first experiment, Bao and colleagues recruited ten adult participants who showed significant interocular imbalance. During a five-day adaptation stage, the participants had a daily three-hour training session, in which they wore an augmented-reality headset that showed them a slightly altered version of their surrounding environment in real time.
The images presented to each eye were identical except for unique patches that were pixelated in each image. The training essentially forced participants to weight the input from each eye equally to be able to process and perceive the complete scene. Participants completed the adaptation training sessions in the laboratory as they engaged in typical everyday activities, such as watching movies, playing video games, eating and walking.
To gauge change in ocular dominance over time, the researchers had participants complete a binocular-rivalry task before the adaptation phase, at the beginning of each training session in the adaptation phase, and at follow-up sessions 24 hours, two days, three days, one week, three weeks, two months, and four months after the last training session. In each trial of the task, the participants saw two images simultaneously, one presented to each eye.
Each image featured a striped grating pattern, with the pattern in one image oriented in a different direction from the pattern in the other image. After seeing the images, participants pressed a key to indicate the direction of the pattern they saw (tilted counterclockwise from vertical, tilted clockwise from vertical, or mixed).
The researchers observed training-related changes in ocular dominance over time. The results indicated that the stimuli shown to the stronger eye became less dominant over time, effectively increasing participants’ interocular balance. Importantly, interocular balance continued to improve in the two months after training ended, and the researchers continued to observe training-related improvement at the four-month follow-up.
“This method manipulates the visual world electronically so as to incorporate training into everyday life,” said Bao. “Several three-hour adaptation sessions produced effects that strengthened when people returned to their normal visual environment after the training ended.”
18 participants involved in a second trial also exhibited improvement throughout the training phase and in the weeks that followed. On average, their improvement in visual acuity was equivalent to being able to read an additional 1.5 lines down on the standard logMAR eye chart.
Findings from a third group of participants indicated that the weaker eye showed improvement in various functions—such as dichoptic motion coherence, visual acuity and interocular phase combination—as a result of training.
Bao and colleagues plan to continue this line of research, investigating the exact mechanisms that drive these training-related effects. They believe their latest findings could have important implications for work in a variety of domains, including clinical ophthalmology, neuroscience, engineering and product development.
The article can be found at: Bao et al. (2017) The Best of Both Worlds: Adaptation During Natural Tasks Produces Long-Lasting Plasticity in Perceptual Ocular Dominance.
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Source: Chinese Academy of Sciences; Photo: Shutterstock.
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