How eyes can reveal early sign of Parkinson's disease

Washington: Turns out, eyes play a crucial role for people with Parkinson's disease.

People with the disease gradually lose brain cells that produce dopamine, a substance that helps control movement. Now, a new study has found that the thinning of the retina, the lining of nerve cells in the back of the eye, is linked to the loss of such brain cells.

Study author Jee-Young Lee said, "Our study is the first to show a link between the thinning of the retina and a known sign of the progression of the disease -- the loss of brain cells that produce dopamine."

Lee added, "We also found the thinner the retina, the greater the severity of the disease. These discoveries may mean that neurologists may eventually be able to use a simple eye scan to detect Parkinson's disease in its earliest stages before problems with movement begin."

The study involved 49 people with an average age of 69 who have diagnosed with Parkinson's disease an average of two years earlier but who had not yet started medication. They were compared to 54 people without the disease who were matched for age.

Researchers evaluated each study participant with a complete eye exam as well as high-resolution eye scans that use light waves to take pictures of each layer of the retina. Researchers found retina thinning, most notably in the two inner layers of the five layers of the retina, in those with Parkinson's disease.

In addition, the thinning of the retina corresponded with the loss of brain cells that produce dopamine. It also corresponded with the severity of the disease.

"Larger studies are needed to confirm our findings and to determine just why retina thinning and the loss of dopamine-producing cells are linked. If confirmed, retina scans may not only allow earlier treatment of Parkinson's disease but more precise monitoring of treatments that could slow progression of the disease as well," said Lee.

A limitation of the study was that the retina scans focused only on a limited area of the retina.

The full findings appeared in the journal Neurology.