January 26, 2009

Space Technology Yields New Cataract Detection Technique

A very blurry photo of two boys, illustrating vision with a cataract A scene as it might be viewed by a person with cataracts (right). National Eye Institute

A compact fiber-optic probe developed for the space program has now been used to create the first non-invasive device for early detection of cataracts, the leading cause of vision loss worldwide.

A cataract is a clouding of the eye lens. The lens focuses light onto the retina at the back of the eye, where images are recorded. The lens is made mostly of water and protein arranged to keep the lens clear and let light pass through. But as we age, some of the proteins can clump together and form a cataract that clouds an area of the lens. Over time, the cataract can grow larger, making it harder to see. When the vision loss from a cataract interferes with your everyday activities, it needs to be removed surgically.

If the subtle protein changes leading to a cataract could be detected early, people might be able to cut their cataract risk by making simple lifestyle changes, such as reducing sun exposure, quitting smoking, stopping certain medications and controlling diabetes. Dr. Rafat R. Ansari, a senior scientist at NASA’s John H. Glenn Research Center and co-author of the new study, first brought an idea to the attention of vision researchers at NIH’s National Eye Institute (NEI) when he learned that his father’s cataracts were caused by changes in lens proteins. Ansari knew of a laser light technique called dynamic light scattering (DLS), which was initially developed to analyze the growth of protein crystals in a zero-gravity space environment. He thought that DLS might also be employed as part of a simple, safe eye test for detecting early protein changes in the lens.

The researchers honed in on a lens protein called alpha-crystallin, which is known to bind to other lens proteins when they become damaged, preventing them from bunching together to form a cataract. People are born with a fixed amount of alpha-crystallin, so if the supply becomes depleted due to radiation exposure, smoking, diabetes or other causes, a cataract is more likely to form.

The scientists created a device that shines a low-power laser light on the lens. The light scattered by randomly moving particles in the lens is measured for 5 seconds. The researchers determined alpha-crystallin’s light-scattering ability and then used animal models to develop a technique for detecting and measuring the amount of alpha-crystallin in lenses.

In their latest study, published in the December 2008 Archives of Ophthalmology, the research team reported the results of the device’s first clinical trial. They tested it in 380 eyes of people from age 7 to 86 years old. The eye lenses ranged from clear to severe cloudiness from a cataract. The scientists found that as cloudiness increased, alpha-crystallin in the lenses decreased. Alpha-crystallin levels also decreased as the participants’ ages increased, even when the lenses were still transparent. Such age-related, pre-cataract changes can’t be detected by currently available tools.

“By the time the eye’s lens appears cloudy from a cataract, it is too late to reverse or medically treat this process,” said Dr. Manuel B. Datiles III, NEI medical officer and lead author of the clinical study. “This technology can detect the earliest damage to lens proteins, triggering an early warning for cataract formation and blindness.”

The DLS technique can help vision scientists assess the effectiveness of anti-cataract therapies. It will also be useful in studies of long-term lens changes and their causes.

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