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Revolutionary idea for testing eyesight could produce more accurate results

BY HEIDI ULRICHSEN When optometrists examine patients' eyes, they put different lenses in front of them to find out which strength gives that person the ability to see an eye chart clearly.

BY HEIDI ULRICHSEN

When optometrists examine patients' eyes, they put different lenses in front of them to find out which strength gives that person the ability to see an eye chart clearly.

But retired Laurentian University physics professor Marcel Leach says he has a much more accurate way of testing the human eye. He plans on submitting his idea to the Canadian patent office.

His eye-testing system is based on the "persistence" theory, where people still see images of objects for a few fractions of seconds after they have looked at them.

"It's a phenomenon whereby if you look at your finger for instance, and remove your finger, for a very short period of time, the image of your finger remains on your retina," says Leach, an acoustics researcher who normally doesn't study optics.

"That time is in the 15 milliseconds range or something like that. The idea, then is to use that phenomenon to come up with or invent a very accurate, precise method for examining eyes."

The usual tests done by optometrists can be inaccurate because people might be wrong about when they are seeing clearly, says Leach.

He came up with the idea after two "botched eye exams" where his optometrist prescribed glasses that failed to correct his vision.

With Leach's test, an optometrist would shine a laser image onto a screen and pulse it.

"Everybody has a different perception time. It doesn't vary that much, but it varies from person to person. It also varies with your vision or your acuity," he says.

"If you start at a persistence period that's a little lower than your eye, you just slowly change or tune the laser. When you hit the persistence time of your eye, the image disappears. There's no question of subjective things like 'is this clear or is it not clear.'"

The optometrist would be able to pick out the most appropriate lens strength through a chart calibrated with the persistence times, Leach says.

The physicist says that he hasn't done any tests to see if his theory works yet, but plans to do so in the near future. Several other Laurentian professors also like his idea.

Leach, who already has a patent on acoustic emissions from materials like ball bearings and sand, says he'll apply for a patent for the eye-testing system as soon as he has the money.

Applying for a patent costs about $25,000, he says.

Every optometrist is going to want this system once it's out on the market, Leach predicts. And hopefully, that's going to make him rich.

"I think if we offer an instrument as accurate and precise as this thing, they should be buying it," he says. "It's a total improvement, there's no doubt about it."