Aug. 5 -- TUESDAY, Aug. 4 (HealthDay News) -- A new type of eye drop appears to protect retinal and optic nerve cells -- and even reverse some sight loss -- in patients battling glaucoma, a leading cause of blindness, new research suggests.

Italian researchers found that the topical use of nerve growth factor, which is easily absorbed by the eye in drop form, spares retinal ganglion cells from nerve damage caused by the build-up of eye pressure associated with glaucoma.

This is "the first evidence that nerve growth factor eye drops may represent a potential treatment for glaucoma," said Dr. Stefano Bonini, professor and chairman of the department of ophthalmology at the University of Rome Campus Bio-Medico.

Bonini and his team reported their findings in the Aug. 3 online edition of the Proceedings of the National Academy of Sciences.

Glaucoma is an often symptom-less grouping of incurable, but treatable, eye diseases that cause vision loss and blindness as a result of slowly building damage to the eye's optic nerve, according to the Glaucoma Research Foundation.

Although people of all ages are vulnerable to the disease, the elderly face a particularly high risk. The Glaucoma Research Foundation notes that glaucoma is the second most common cause of blindness worldwide. About 4 million Americans have the disease (about half don't know it), and roughly 120,000 have lost their vision as a result. In sum, glaucoma accounts for roughly 10 percent of all blindness in the United States.

Although current interventions can reduce the troublesome eye pressure associated with glaucoma, thereby slowing its progression, no treatment to date has succeeded in restoring vision lost to the disease.

Exploring ways to do that, the authors observed that nerve growth factor -- a protein found in human tissue -- previously had been shown to be beneficial when treating the brain tissue of Parkinson's and Alzheimer's patients. Because of similarities in development, glaucoma is sometimes called "the ocular Alzheimer's disease," they noted.

The current work focused on using nerve growth factor in eye drops to treat dozens of rats in whom glaucoma was induced.

Testing two different amounts of nerve growth factor, the team documented a significant drop in the rate of retinal cell death, particularly with the higher dose.

The authors then tested the nerve growth factor eye drops on three patients with advanced glaucoma, each of whom had suffered significant visual deterioration.

A battery of eye function tests conducted before treatment with nerve growth factor eye drops, three months after treatment began and three months post-treatment demonstrated that the vision of two of the patients actually improved, while the vision of the third patient stabilized following treatment.

Furthermore, the observed improvements in visual field, optic nerve function, contrast sensitivity and visual acuity remained in place 18 months after the first eye drops were administered, the researchers reported.

Despite the encouraging results, Bonini cautioned that the novel nerve growth factor approach to halting glaucoma disease will not be available to consumers in the immediate future.

"These impressive findings are promising, but still far from any broad clinical application, since nerve growth factor is not currently available for clinical use," said Bonini. "And these pilot clinical results should be confirmed in large clinical trials.

But the study team suggested that the findings could theoretically pave the way for new options in treating eye disease and a range of other neurodegenerative diseases.

Rando Allikmets, a professor of ophthalmology, pathology and cell biology at Columbia University in New York City, applauded the research team for its effort to develop a better treatment for glaucoma.

"The science concerning glaucoma is very much less clear than, say, that regarding age-related macular degeneration," he said. "So it is true that there are some treatments for glaucoma, and they are sometimes effective at slowing down or delaying the progress of the disease," Allikmets noted.

"But that's it. The available drugs don't get at the actual disease," he added. "So it's not clear if this work will hold up under further study, but if these researchers were able to actually reverse some of the actual vision loss due to glaucoma that would be a very strong statement."

More information

For additional information and resources on glaucoma, visit the Glaucoma Research Foundation.

SOURCE: Stefano Bonini, department of ophthalmology, University of Rome Campus Bio-Medico, Italy; Rando Allikmets, Ph.D., the William and Donna Acquavella associate professor of ophthalmology, director of Molecular Genetics Laboratory, Columbia University, New York City; Aug. 3, 2009, Proceedings of the National Academy of Sciences, online