Vision Health
(Globe & Mail insert)
Research continues to pave new ground
Along with the urgent need to develop and support new models for eye care in Canada, basic and applied research in the field also demands far more emphasis.
"We're clearly not doing our share in terms of a first-world country, especially as we know how serious these [vision-health] problems are in relation to an aging population," says Dr. Martin Steinbach, director of Vision Science Research at Toronto Western Hospital.
"It was dismaying when we found out in 1999 that funding for this area was about $14-million per year in Canada," he continues. "In the U.S., the National Eye Institute alone receives $632-million (U.S.)."
The recent creation of the Canadian Institutes of Health Research will be of some help but more public awareness and political support is critical. Improved technology alone, declares Dr. Steinbach, can't do it.
"There are surgical techniques now which would have been unheard of 10 years ago," he remarks, "but that's not going to work in the bulk of the diseases."
Nonetheless, Canada does have distinguished researchers in vision science
doing important work. A few examples:
AGE-RELATED
MACULAR DEGENERATION
Dr. Jill Hopkins, retinal specialist, Sunnybrook & Women's College
Health
Sciences Centre
A leading cause of vision loss, age-related macular degeneration sometimes comes in a "wet" form involving leaking vessels in the eye.
"In the past, we used to use thermal lasers, which worked by scarring the retina and the vessels behind the retina," explains Dr. Hopkins, adding that the treatment was only suitable for a minority of patients.
Today, an innovation called photodynamic therapy (PDT) involves injecting into the body a drug selectively absorbed by these retinal vessels and then activated by a cold laser. "You get much smaller, drier, flatter scars," Dr. Hopkins reports. "Photodynamic therapy has opened up a much bigger group of people who we can now treat."
Could that group become bigger still? PDT has been proved effective for "classic" or well-defined leakage but more scientific study is needed for its use on patients with occult leakage involving multiple pinpoints throughout the retina.
Dr. Hopkins is among the investigators across North America now enrolling patients in a clinical trial to learn more. She is also involved in studying the potential role of a growth hormone inhibitor, Sandostatin, which, she says, "may be able to reduce the progression that leads to diabetic retinopathy."
GLAUCOMA
Prof. C. Ross Ethier, Canadian Research Chair in Computational Technology,
University of Toronto
The second-most common cause of blindness in Canada, glaucoma is usually associated with raised intraocular pressure in the eye. While treatment focuses on lowering that pressure, the mechanisms of glaucoma are poorly understood.
A bioengineer who collaborates with clinical ophthalmologist Dr. Graham Trope, scientist and optometrist Dr. John Flanagan and Dr. Arthur Sit, an ophthalmology resident and engineer, Prof. Ethier is engaged in three distinct glaucoma investigations, looking at how pressure becomes elevated, how that pressure damages the eye and how to create a refined mechanical device to help relieve pressure.
The latter effort entails developing a more effective glaucoma shunt valve to drain fluid from the eye: "There are a number of devices available in the market," notes Prof. Ethier, "but unfortunately there are some technical issues with them."
Meanwhile, why does pressure get elevated in the first place? "It's not well understood at all what controls the pressure in a young, healthy eye," says Prof. Ethier, who is now studying the cells lining Schlemm's canal to determine their role in both normal eyes and those with a common form of glaucoma.
It is not yet clear even how pressure damages the eye. One suspected factor Prof. Ethier is investigating is the tendency of the supportive tissue within the optic nerve to deform under pressure, either directly damaging that nerve or impairing localized blood flow.
DIABETIC RETINOPATHY
Prof. Chris Hudson, head of the Multi-Disciplinary Lab for Research of
Sight-Threatening Diabetic Retinopathy, Toronto Western Hospital
As Canada experiences an epidemic of diabetes, a surge in vision loss through diabetic retinopathy is in the cards as well. Proliferative retinopathy spurs a growth of abnormal blood vessels at the back of the eye, while diabetic macular edema creates a thickening of the retina as nearby vessels begin to leak.
"Basically, macular edema is a very difficult entity to diagnose and to monitor," Prof. Hudson explains. "When the retina thickens, it's still clear."
Novel, non-invasives instruments to measure retinal thickness and the rate of retinal blood flow are now available, however, and Prof. Hudson and his multidisciplinary team propose to use these instruments to monitor macular edema in Type 1 and Type 2 diabetics. "The study," he says, "will establish early markers of the development of macular edema, will permit the earlier treatment and improved monitoring of macular edema and will significantly increase our understanding of the mechanisms that promote sight loss in diabetic eye disease."
A clinical-vision scientist whose background is optometry, he adds that, "we're monitoring the natural history of macular edema because we don't even know what profile that development has - is it continual, is it espisodic, can it reverse?"
GENETICS OF EYE DISEASE
Dr. Michael Walter, associate professor of ophthalmology, University of
Alberta
If treatment for eye disease is to advance, much more has to be understood about its essential mechanisms, an end to which researchers such as Dr. Walter are engaged.
"When a patient walks in with an eye disease," he observes, "we have a name for it but we don't necessarily know what causes it. With such understanding, we can develop more effective treatment."
Glaucoma is a prime example and one of the areas Dr. Walter is most involved in.
"Whenever a disease is very common like glaucoma, it means there are multiple ways in which we can get there [to the pathology]," he says. "All of our treatments both surgical and medicinal for glaucoma are related to reducing pressure. But what percentage of patients with glaucoma get highpressure is controversial." Several genes have now been identified as causes of glaucoma, a disease for which "until about 20 years ago it wasn't understood that it had any hereditary component," says Dr. Walter, adding that it may prove that as much as 50 per cent of glaucoma cases have a hereditary factor.
