March 1, 2007 Macular degeneration, a condition that occurs in the retina and most affects an individuals' ability to drive and read, is being better diagnosed by two scanning techniques that much more useful in combination. The Scanning Laser Ophthalmoscope (SLO) gives in-depth images of the retina's surface, and the Optical Coherence Tomography (OCT) shows a cross section of the same location.
For many people, getting older comes with the dread of age-related health problems, and loss of vision is one of the most common ones. But a new, high-tech test is changing the way eye doctors diagnose their patients.
Eighty-seven-year-old doctor Paul Singer drives everywhere, everyday. "Driving is a very important part of your life when you live in the suburbs," he says.
But a couple of years ago, Singer started losing his vision and had to stop driving. "It's a tremendous handicap," he says. "It's very depressing. It's something that you have to adjust to."
Singer had age-related macular degeneration. AMD affects the macula in the center of the retina and is responsible for central vision. We use it most when driving or reading.
For years Singer was told he had an early stage of the disease. But then treatments failed.
"Well, he wasn't being misdiagnosed. We knew that he had a form of macular degeneration. But he had what's called an occult macular degeneration," ophthalmologist Richard Rosen, M.D., tells DBIS.
The occult form is a slow-leaking, wet version of AMD.
Rosen, Vice Chairman of the Department of Opthamology at New York Eye & Ear Infirmary, had a hard time detecting the less-common form of the disease using standard scans. Now, a new scanning laser ophthalmoscope (SLO) gives in-depth images of the retina's surface, and the optical coherence tomography (OCT) shows cross-sections of the same location.
Individually, the tests are limiting, but "two instruments together allow us to correlate the surface detail with the internal detail," Rosen says.
Using the OCT/SLO imager led to a different diagnosis for Singer. And with the right medicine, he recouped about 80 percent of his vision. "It has made a difference in my life in the sense that I can resume my life as I had been living it," he says. Now he's back to driving and reading his daily paper, tasks he has newfound appreciation for.
The combined OCT/SLO technology is becoming more widely available. So far, several hospitals in New York, Pennsylvania and California have it. It is covered by most insurance.
BACKGROUND: Researchers at the New York Eye and Ear Infirmary have developed a new diagnostic imaging device for the eye that combines two techniques -- known as optical coherence tomography and scanning laser ophthalmoscopy -- to detect and precisely locate hard-to-spot problems in the retina, particularly macular degeneration, a major cause of blindness in the United States. Early diagnosis allows these problems to be treated in their earliest stages. A commercial version of the OCT-SLO device is now available for patients at various locations around the country. The researchers are now using OCT-SLO in combination with electroretinography to measure electrical response in the retina.
HOW IT WORKS: OCT-SLO not only painlessly produces very high resolution images of the retina in just a few minutes; it also provides a way to precisely localize aberrant blood vessels which cause the disease so treatments can be localized and better monitored. Both OCT and SLO have been available separately for years, and both involve back-scattered photons (particles of light) to produce images.
ABOUT THE RETINA: We can see because light reflects off objects in our surroundings and enters the eye through the pupil. The light is then focused and inverted by the cornea and the lens, and projected onto the back of the eye. There we find the retina, which is lined with a series of photoreceptors that convert the light signal into a neural signal. Ganglion cells then transmit those signals to the brain via the optic nerve.
BENEFITS: First developed at the Massachusetts Institute of Technology, in Cambridge, in 1991, OCT allows physicians to image and analyze tissue onsite at the time of surgery, without the need to send tissue samples to the lab, having to wait until the surgery is over for results. This in turn could lead to the need for repeat surgery. Its first clinical application was in optometry, to optically analyze the retina and cornea. The technique can also be used to image the lymph nodes to check for the spread of breast cancer. Ultimately, OCT could replace needle biopsies altogether.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.