Kevin Duffy, an associate psychology professor at Dalhousie University, has been studying the topic, formally known as amblyopia, since he was a graduate student 15 years ago.
Last month his research findings, conducted with fellow professor Donald Mitchell, were published in the journal Current Biology.
“I’m really interested in plasticity of the brain, and this is a natural way for me to study the plasticity through the brain – through amblyopia,” said Duffy, 40, who is also a neuroscience program advisor at the university.
“As it turns out, a nephew has been diagnosed with the condition, so that makes me more motivated than ever, but that’s not the reason why I got into it.”
Amblyopia occurs early in life and those diagnosed with amblyopia experience abnormal vision. About four per cent of the population has amblyopia.
“If you cut a ping pong ball and put one half over an eye, what you see is blurry and you may only be able to see silhouettes,” said Duffy, adding the brain still has some developing to do and proper development comes when “good, healthy, crisp vision reaches the brain.”
If that vision is blocked, the brain develops abnormally, he said.
One way doctors have tried to correct the problem is by patching the good eye, meaning the brain and abnormal eye work harder.
“Patching can be effective and you can get better vision, but people with amblyopia will still have problems up until they die.”
While a lot of scientific research is done on mice and rats, cats have a higher visual acuity, about 10 times higher, than rats. Duffy and Mitchell used kittens for their research. All the kittens are bred at Dalhousie for the purpose of research and the work is approved by the Canadian Council on Animal Care, a federal regulatory body that oversees the ethical use of animals in science throughout Canada.
Having done quite a bit of surgical procedures during a post-doctorate at Harvard Medical School, Duffy refined a technique for closing lids of cats’ eyes – a non-invasive surgery involving three sutures under anesthesia.
“There’s a thin membrane and we close their eye with the sutures. There is no harm to the eye or the eyelid. The eye stays closed for seven days, long enough to produce changes in the brain. When the eye is opened, that one is amblyopic and one is normal,” said Duffy.
The kittens are then broken into two groups – one group is put into total darkness with their mother and littermates.
“They’re kept in total darkness, but there is a radio playing and we have an infrared light and a camera so we can monitor them. We also have workers trained to navigate in the dark that look after them and continually monitor their health.”
After 10 days, the group is taken out of the darkness.
“What we saw happen is that the normal eye was losing vision as a result of the darkness,” said Duffy. “About 70 days later, both eyes had improved and acquired normal vision.
“But the second group was more exciting.”
That group of kittens had their eye opened after seven days. They were normal kittens for the next five weeks.
“We measured their vision and their amblyopic eye never recovered,” Duffy said.
At the end of the five weeks, the kittens were put in total darkness for 10 days.
“The darkness didn’t reduce the vision in their normal eye, and that’s fantastic news. With the amblyopic eye, after seven days of being out of darkness, the eye was totally back to normal.”
The findings are a step toward a possible treatment for amblyopia in humans, but more needs to be done.
“We need to know what’s happening in the brain with the darkness. There must be something really profound happening in the brain. It’s almost as if the brain is going back to an earlier stage in development and resetting itself,” said Duffy.
He also said there are a number of other parameters that need to be figured out before seeing if it has the same affects on humans, such as whether a lesser period in the dark will yield similar results, if it has to be complete darkness, if it would be as effective if the person could be taken out for a short period of time, or if it would have to be 10 days of complete darkness.
“Imagine if you had a son or daughter with amblyopia. You would be concerned also about putting them in darkness too early in life,” said Duffy. “What if it compromised the good eye? All that has to be worked out.”
It’s something that Duffy and Mitchell will continue researching, despite some of the emails Duffy has received being negative toward using cats in the process.
“Some people don’t agree with it, and I respect that. I usually ask them if they would rather not use them and not having any advancements in medical procedures.”
All the kittens that have been used in the research have been adopted.
Twitter: @TDNRaissa
ABOUT AMBLYOPIA:
- Amblyopia, also known as lazy eye, is a vision development disorder in which an eye fails to achieve normal visual acuity, even with prescription eyeglasses or contact lenses.
- Amblyopia begins during infancy and early childhood. In most cases, only one eye is affected. But in some cases, reduced visual acuity can occur in both eyes.
- Particularly if lazy eye is detected early in life and promptly treated, reduced vision can be avoided. But if left untreated, lazy eye can cause severe visual disability in the affected eye, including legal blindness.
- Amblyopia affects about four per cent of the world’s population
Source: www.allaboutvision.com
