Cécité: actualité internationale

La cécité...
Actualité internationale
2008

mars

Detecting Eye Disease Early

ADIT,

March 05, 2008
A new technique could be used to diagnose and treat patients before they begin to go blind.
By Anna Davison

     State-of-the-art imaging equipment is being used by researchers at the University of Michigan to spy on cells in the eye in order to detect eye disease at a very early stage. They say that their technique could pick up signs of serious problems, such as glaucoma, early enough for patients to be treated before their vision is affected.
     The researchers' method looks for metabolic changes in the cells of the retina and optic nerve due to disease. Those effects begin long before the first obvious signs normally hit, such as vision loss or structural abnormalities.
     Using a sophisticated camera system coupled with customized imaging software, the researchers were able to detect changes in the eyes of patients with a brain disorder that can affect the optic nerve, and in people with glaucoma and diabetic retinopathy, two of the most common causes of blindness.
     "We believe that this is going to be useful in a variety of diseases that affect the eye," says Victor Elner, an ophthalmologist and pathologist at the University of Michigan. The new test takes less than six minutes, and Elner says that it could be developed as a "point and shoot" system in which images are analyzed on a computer, either in an ophthalmologist's office or at a centralized location.
     If the technique proves effective, "it could provide an early warning that cells have become sick," says Joseph Rizzo, a neuro-ophthalmologist at the Massachusetts Eye and Ear Infirmary, who was not involved in the work. That would allow physicians to start aggressive treatment before patients begin to go blind. If they are treated early, progressive eye diseases like glaucoma can be controlled, which slows or prevents damage to the eye and preserves vision. "It's potentially truly wonderful," Rizzo says of the detection technique.
     In a study reported in the current issue of Archives of Ophthalmology, Elner and four colleagues at the University of Michigan tested their imaging technique on six women who had recently been diagnosed with a condition called pseudotumor cerebri (PTC), a disorder in which a buildup of pressure in the brain causes symptoms similar to those of a brain tumor. In some PTC patients, pressure on the optic nerve can lead to vision loss.

     The researchers began by administering standard vision tests to the women. They all had good visual acuity. Visual field testing, which measures the area seen by the eye and is routinely used to screen for diseases like glaucoma, indicated subtle abnormalities in some of the women.
     Elner and his colleagues then used their new metabolic imaging system to check the health of cells in the women's eyes by shining a blue light on their retinas and looking for green fluorescence given off by oxidized proteins in dying cells. They measured the intensity of this fluorescence and found that it was significantly greater--60%, on average--in the eye that was most affected by the disorder. There was no significant difference between the measurements in the eyes of women without PTC. "Diseases seldom affect both eyes the same," Elner says. "We generally pick up an asymmetry in all kinds of diseases."
     The new technique proved as effective as, or often superior to, the standard tests performed on the women. Elner and his colleagues are also studying the method in patients with glaucoma, which damages the optic nerve, and diabetic retinopathy, which involves changes in the blood vessels in the retina, but they have not yet published the results of those studies.
     "This technique is intriguing," says Sunil Srivastava, an assistant professor of ophthalmology at Emory University's Eye Center, who was not involved in the work. "There's a lot of potential for it." But, he says, "what's needed is going to be lots of data looking at patients with early disease, and following them with it."
     Because the new imaging system could be used to track metabolic changes in the cells of the eye, Elner believes that it may also be useful in drug discovery. The effects of potential treatments could be tracked over weeks, he says, rather than having to wait months to observe changes in vision, or in the structure of the eye.
     "This will be a faster method of screening for drugs," Elner says.
     It could also enable physicians to closely monitor the effect of drug regimes on their patients, he adds, so that they can figure out the very best treatment strategy.