An elderly woman struggles to regain hand-eye coordination after a stroke. A young boy deals with the frustration of dyslexia while learning to read. Like these two individuals, millions of Canadians face the daily challenges that accompany vision-related diseases and disabilities.
How can these individuals deal with the daunting tasks ahead of them when they involve not just the eyes and the external environment, but also the brain and sometimes the whole body?
Enter a technological revolution. At the CFI-supported York University Centre for Vision Research (CVR), scientists are now able to monitor and control the factors linked to vision as never before. It's research that's bringing into focus the causes of vision-related problems including dyslexia and those due to brain damage.
As part of his work as Associate Director of CVR, Dr. Douglas Crawford is using state-of-the-art techniques to study the impact of stroke-related brain damage on hand-eye co-ordination. To do this, he's using a highly sensitive eyeball tracker combined with a device called an Optitracker.
The Optitracker is providing a level of detailed focus that's paying off. Working with stroke patients, Dr. Crawford's lab group recently discovered how brain damage can affect a person's ability to store visual space for the purpose of hand movement. For these people, visual information for orientation is literally lost with a sideways glance. "Simply by making an eye movement, one of these brain-damaged patients might cause the memory representation in their brain to get remapped into the damaged part of the brain," says Crawford.
The centrepiece technology at CVR is the Immersive Visual environment at York—also known as IVY. This custom-built virtual reality box is designed and operated by a team led by computer scientist Dr. Michael Jenkin. It has the distinction of being Canada's only life-size virtual reality environment. IVY enables Canadian researchers, for the first time, to study and manipulate natural scene vision—the full range of what a moving person sees. Participants enter IVY through a removable back panel. Once inside, they can view each of IVY's six, 2.5 metre-long sides, which act as projection displays. What a person sees is completely at the mercy of the controllers—and very convincing. It's so real, in fact, that participants duck when they see objects careening towards them. "In IVY, a person is free to walk around and turn their head and see behind them just as in the real world. So it's a truly immersive experience," says Dr. Laurence Harris, a professor at the Centre for Vision Res arch.
Harris is using IVY to study the role of vision in how we determine which way is “up.” While it might seem obvious, knowing how we orient ourselves and the objects we see in three-dimensional space is important in a number of areas and applications—from understanding dyslexia to helping astronauts determine direction in zero gravity
IVY has enabled Harris to create a series of experiments in which subjects' visual “up” cues are distorted. In one experiment, participants must turn a virtual ball upright in a virtual room that's tilted up to 90 degrees from the vertical.The research is showing that our sense of up is a compromise between our eyes and our bodies. "The results of many experiments come together to demonstrate the same point," says Harris. "Your sense of orientation and your perception depend on the orientation given by vision, the orientation of your body, and gravity."
What is vision? It involves a lot more than meets the eye, says Dr. Harris.
"Vision on its own doesn't really exist," says Harris. "The act of seeing in isolation doesn’t make any sense. What happens on the retina has to be combined with other senses to be actually used."
Exploring how visual information interacts as part of our integrated sensory and muscle systems underlies the interdisciplinary research at CVR. It's also crucial to understanding the causes of vision-related diseases and disabilities. Harris notes that while we are more aware of what's in our centre of focus, information seen from the "corner of our eyes" is also crucial to proprioception and our ability to orient ourselves. "As you move around, your peripheral vision is important in telling you your direction, speed, and orientation," says Harris. "These are things that you usually take completely for granted."
That is until an event, such as a stroke, makes even the most basic physical orientation seem like a Herculean task. This can include just reaching out to pick up a cup of coffee from the kitchen table. "Eye movements have a huge impact on how the arm is controlled," says Dr. Crawford, a pioneer in the study of hand-eye co-ordination. "So investigating visual-motor processes is essential for understanding what goes wrong in neurological diseases."
When potential corporate, hospital, or academic partners get a look at the Centre for Vision Research's work—especially with the Immersive Visual environment at York (IVY)—they rarely need to see more before joining in. "Industries have been excited about using IVY," says Dr. Laurence Harris.
The list of partners and participants is already substantial. IVY has been used for gravity and vision-related work sponsored by the Canadian Space Agency and NASA. One of the early collaborators in IVY research is Good Vibrations Inc., an Ontario-based company that develops and provides mechanical engineering services to the aerospace and defence sectors. The company is using IVY as a test bed for a “galvanic vestibular stimulator,” a device that makes you think you're moving when you're not. The prototype device is attached to both ears and uses low-level electrical current to stimulate the vestibular system and induce a sense of motion.
CFI support has enabled Dr. Douglas Crawford to extend his CVR research directly into Sunnybrook hospital in downtown Toronto. Working with Sunnybrook's Dr. Sandra Black, Crawford has set up an Optitrack system at the hospital for research with stroke patients. "The patients are often quite willing to take part in the research because they appreciate much more than most people just how debilitating these problems are, and how much more we need to know about them in order to develop better treatments," says Crawford.