The Eye's True Colors

Color cells in the eye might mean advances in finding retina problems

(RxWiki News) Sometimes seeing the forest requires first seeing the trees - and the leaves on those trees. A new way to "see" regular changes in eye cells might lead to detecting retina problems as well.

Our eyes see color because of specialized cone cells that line the inner surface of the eyeball in the retina.

Each if these cone cells has a section called the outer segment made up of tiny discs stacked like pancakes that sense the light coming in.

Throughout the day, this stack of discs regularly lengthens and shortens. Researchers might be able to use information about these changes to differentiate between healthy and diseased cells in the retina if they can learn the ins and outs of these outer segment fluctuations.

"Eye exams are an important part of maintaining your health."

The problem has been how to measure such tiny changes in such tiny parts of microscopic cells in the eye - until now. Dr. Ravi Jonnal and colleagues at the Indiana University have found a new way to apply existing technology to determine how these outer segments expand and contract.

Eye doctors already use a technique called optical coherence tomography (OCT) to scan retinas with beams of light. They split a beam of light in half, using one half for reference and shooting the other half off the retina.

When the two halves come back together, doctors can compare the data to learn about the retina. Jonnal's team simply looked closer at the specific data coming from two different points in the cells - the top and the bottom of the outer segment.

Over several hours, the scientists were able to measure the microscopic changes in cone cells' outer segments in two people with healthy vision. "Using custom software for registration and tracking, these microscopic changes are monitored in hundreds of cones over time," the paper's abstract states.

They discovered that these outer segments grow at a rate of about 150 nanometers per hour, 30 times faster than human hair grows. Knowing this rate and having a method to measure these outer segment variations might help doctors recognize retina problems in people with abnormal variations.

The research paper appears in the December 13 issue of Biomedical Optics Review. Funding for the study was provided by the National Eye Institute grants. No information was provided regarding additional costs of this technique above normal operating costs of OCT scans.

Review Date: 
December 30, 2011