People with eyesight disabilities may now have a legitimate excuse for playing video games.
A team of researchers, including an Ohio State professor, has developed a video game training method that can improve the vision of individuals with a lazy eye and poor depth perception.
The research, funded by the National Institutes of Health, is based on over 20 years of basic science studies of binocular depth perception, according to OSU optometry professor Dr. Teng Leng Ooi.
“An advantage of having two eyes is the ability to have binocular depth perception, i.e., 3D depth perception,” Ooi said in an email. “Good binocular depth ability is vital for our performance in a number of daily activities (e.g., chopping and parallel parking), in sports (e.g., shooting a ball into the hoop and catching a football) and in selected vocations (e.g., dentistry, piloting and carpentry).”
The team’s research was conducted over a 10-month period. According to Ooi, participants went through four phases: a pre-training test, training with the video games, a post-training test and a retention test, which was conducted several months after the completion of the training.
The training phase varied from 15 to 30 sessions, depending on the severity of the lazy eye. Ooi and her team studied the complex brain network involving both the excitatory and inhibitory signals between the two eyes. When properly balanced, these signals govern binocular vision and produce 3D depth perception in the eyes. When an imbalance exists, a person will have sensory eye dominance.
“Professor Ooi and I have studied sensory eye dominance for 20 years,” said Dr. Zijiang He, a psychological and brain sciences professor at the University of Louisville, in an email. “Our first step was to develop psychophysical methods to measure sensory eye dominance and understand its underlying mechanisms. Our subsequent step was to seek a treatment to reduce sensory eye dominance, and thus, improve vision.”
Sensory eye dominance is a person’s preference to use one eye. According to Ooi, people with normal vision can have mild to moderate degrees of sensory eye dominance. People with amblyopia, or lazy eye, have strong sensory eye dominance.
Lazy eye is the loss or lack of development of central vision in one eye that is unrelated to any eye health problem and is not correctable with lenses, according to the American Optometric Association’s website. Lazy eye is often associated with crossed-eyes or a large difference in the degree of nearsightedness or farsightedness between the two eyes.
Roughly two to three percent of the U.S. population has lazy eye, Ooi said.
Methods of treating lazy eye are usually approached by forcing the lazy eye to see by reducing vision in the strong eye, she said.
Traditionally, eye patching and atropine eye drops were treatment methods that “deprived or penalized” the vision of the strong eye by having the patient place an eye patch over the strong eye, or having the strong eye’s vision blurred through the use of eye drops, Ooi said. These treatment strategies, during which the dominant eye remains completely unused, are called “push-only” methods.
The goal of these “push-only” methods are to solely improve the vision of the weak eye.
Ooi and her team used a different treatment strategy, called a “push-pull” method, which simultaneously strengthens the vision in the weak eye and trains it to suppress the vision in the other eye, which prevents the strong eye from doing all of the work.
Ooi’s “push-pull” method was implemented through two types of video games: a Pac Man-style “cat-and-mouse” game and a “search for oddball” game. With this “push-pull” method, Ooi and He created an alternative treatment for patients with vision impairment.
“The video games are designed in such a way that the weak eye views a strong target that reliably attracts attention to it to enable it to see the target,” Ooi said. “The strong eye is also presented with a target, but it is not seen by the observer because the weak eye suppresses the vision of the strong eye from consciousness.”
The two objectives of the games were to force the weak eye to see (push) and force the weak eye to suppress the vision of the strong eye (pull), she said.
“They collectively train the two eyes to work better together, to become less imbalanced and to improve depth perception,” Ooi said.
Ooi and her team found that the games resulted in reduced sensory eye dominance and improved depth perception of subjects with normal vision and subjects with lazy eye. According to Ooi, the subjects with lazy eye saw an improvement in the visual acuity (sharpness) of their lazy eyes.
An important motivation for developing the push-pull method into video games was to make it enjoyable because learning is most effective when the participants are having fun, He said.
“In our previous non-video-game studies, our participants often had to sit in the lab to run 600 to 1,000 trials a day (one to two hours),” he said. “Doing so could be potentially boring, since the training stimuli were simple images and the tasks were quite repetitive. To overcome the potential factor of boredom, we decided to design the video games to make training fun.”
The video game treatments have only been used by adults, but can potentially become patients’ preferred treatment, He said.
In addition to this video game study, Ooi, who came to OSU last July, has made many contributions to the research done at the university’s College of Optometry, said Kara Zadnik, the college’s dean.
“As one of our newest faculty members and researchers, Dr. Ooi immediately hit the ground running with her research contributions,” Zadnik said in an email. “Her work is groundbreaking and will make a real difference in the delivery of eye care to patients.”
Ooi’s research, entitled “Resetting the Interocular Inhibitory and Excitatory Balance with a Novel Video Game Based on the Push-Pull Perceptual Learning Protocol,” was presented at Neuroscience 2014, the annual meeting of the Society for Neuroscience, held Nov. 15 – 19 in Washington, D.C.
Yong Su of Salus University in Pennsylvania also contributed to Ooi and He’s research.