Vision research:
From the lab to the clinic
Age-related vision loss has been called North America's newest epidemic. As baby boomers age, vision loss is set to become an even bigger public-health issue. There are no cures, no ways to restore sight to those with age-related blindness as a result of such major conditions as diabetic retinopathy, age-related macular degeneration, and glaucoma.
In a study entitled Vision Problems in the U.S., released in 2002 by the National Eye Institute, it was estimated that more than one million Americans aged 40 and over were blind, and an additional 2.4 million were visually impaired. These numbers were expected to double within 30 years as baby boomers move into old age. Canadian baby boomers are also developing eye diseases at alarming rates. Their chances of developing irreversible age-related blindness by age 75 is higher than 1 in 4.
The need for research is clear. Because genetics plays a role in most of the major eye diseases, ocular genetics has become an important tool in understanding these diseases. In the 1970s the University of Alberta established a specialization in ocular genetics that has been strengthened over the years as key researchers have been recruited.
One of the more recent recruits is Dr. Yves Sauvé, an electrophysiologist who joined the university in 2005. He studies the electrical properties of biological cells and tissues, and has a particular interest in using electrophysiological techniques to assess degeneration in the visual system and to devise appropriate therapies.
Age-related macular degeneration, the leading cause of blindness in the elderly of the Western world, is the main area of his research. Dr. Sauvé works with a model that closely mimics the disease—a mouse with a mutation. A mutation is a change in DNA sequencing; it can occur spontaneously in nature, or it can be brought about deliberately in the lab. Dr. Sauvé's model involves a particular gene that is linked with the production of polyunsaturated long-chain fatty acids. Working with the University of Alberta's Dr. Tom Clandinin, an international expert in the metabolism of fatty acids, Dr. Sauvé has begun small-scale trials with the mutated mice, enriching their food with a particular omega-3 fatty acid which is essential for vision. Results show that degeneration of the retina slows down. "We're very excited by the results, but this is very early going," notes Dr. Sauvé. "We don't yet understand how vision deteriorates in [these mutated] mice and how this deterioration might be delayed by dietary supplementation. We are not ready to translate this to humans—but our results to date are promising."
As part of this work, Dr. Sauvé's team is developing tests to detect early signs of vision loss in age-related macular degeneration. His main tool is the electroretinogram, which measures the response of the retina to light (See "Cool Tools"). It can distinguish between the response of the cones, cone-shaped structures in the eye which function in bright light and detect colour, and the rods, which are used in night vision and peripheral vision. "When patients notice something wrong with their vision, it's usually rather late—when the cones have been affected," he explains. "We have preliminary evidence that there is a slight rod dysfunction before that, but it goes unnoticed. We think we may be able to pick up this problem using an electroretinogram."