Researchers at Duke University Medical Center have developed a high-resolution imaging tool that can identify patients at risk for glaucoma decades before the disease claims their eyesight.

"This new instrument that we have designed in collaboration with biomedical engineering allows us to look at the drain structures of the eyeball without touching the eyeball," Dr. Sanjay Asrani, associate professor of ophthalmology at Duke Eye Center in Durham, N.C., told FOXNews.com.

Glaucoma, which affects nearly 500,000 people in the U.S., puts pressure on the optic nerve and can cause irreversible blindness. The device, called fourier domain optical coherence tomography, can detect narrow angle glaucoma, which is the most serious form of the disease.

"I feel like it saved my vision,” said Martha Zollicoffer, 71, of Henderson, N.C., whose left eye was already robbed of vision due to glaucoma. “If I'd had sudden glaucoma with the state that my (right) eye was in, I could've been blind.”

Click here to watch a video about this new device.

There are no symptoms associated with open-angle glaucoma — but narrow angle glaucoma can present headaches, blurred vision and seeing colored halos or colored rings around lights in the evening, Asrani said. If you have these symptoms, you should see an ophthalmologist immediately.

With glaucoma, the pressure in patients’ eyes can suddenly go to an extremely high level. If this attack is not treated immediately, the patient can go blind within a few hours.

But if a person is at risk for the disease, Asrani said, a two-minute laser treatment can prevent it altogether -- 15 or 20 years earlier.

“It’s not bad at all," Zollicoffer said. “It was scary because they were working on my good eye… but it was not painful.”

Traditionally, doctors test for glaucoma with a gonioscopy, in which a special contact lens is pressed to the eye, enabling doctors to see if the drain (angle) is narrow and expected to close in the future.

There is potential for error with this test, because when the gonioscope lens is pressed against the eye, it can make the drain appear to be opened when it’s actually not.

Also, the bright light of the microscope used can make the pupil constrict and distort the angle of the drain.

The new technology, which was featured in the June issue of Archives of Ophthalmology, allows doctors to make a 2D cross-sectional image of the eye with high-resolution, high-speed beams of light without touching the eyeball, according to a news release. It also uses software that can zoom in on very detailed drain structures.

"Because it is done with infrared light spectrum rather than artificial light, we can check the drain with the room lights on and off to know what patients experience in real dark and light settings," Asrani said.

"It's also a great tool to show the patients what we are seeing. They can see how narrow their drain is, and understand the necessity of preventive procedures such as laser surgery, which can open the drain."

There are some drawbacks, though. The device cannot look at the drain from 360 degrees, as the gonioscope can, and it cannot detect new blood vessel growth. But the technology will help doctors learn more about the disease, develop new surgical techniques and assist in making more accurate diagnoses.

Without this device, Asrani said, doctors might miss warning signs. He compared it to cardiologists practicing before the era of angiography.

"I think it will save a lot of people’s vision, and I think that’s very important," Zollicoffer said.