The discovery of a surprise lurking in the retinas of colorblind people may have ramifications for understanding a number of eye disorders. Using a technique called “adaptive optics,” which was originally developed to help astronomers see more clearly through the Earth’s atmosphere, researchers at the University of Rochester have discovered that as many as one-third of the light-detecting “cones” in a colorblind person’s eye can be missing, yet amazingly, visual acuity appears unaffected. The work is published in a recent issue of the Proceedings of the National Academy of Sciences.
“Not only are we excited to show how this method can reveal us living cells in a way never before possible, but it’s revealed a mystery with profound implications,” says Joseph Carroll, a postdoctoral fellow at the Center for Visual Science at the University of Rochester and lead author of the paper. “If a third of the light-receiving cells in your eye are absent and you don’t even notice it, it means that when a patient complains to a doctor about waning light sensitivity, then the damage must already be very serious.”
The findings were possible thanks to a laser-based system developed by David Williams, director of the University’s Center for Visual Science, and colleagues at the University over the last decade that maps out the topography of the inner eye in exquisite detail. The team built on technology known as adaptive optics, initially proposed by astronomer H. W. Babcock in 1953, then developed by the U.S. military to clear up images from spy satellites. The idea is to correct for aberrations in the atmosphere so that rays of light travel in parallel lines and converge at a single point, delivering a sharp image. Astronomers use the technique in telescopes to grab ever-better photos of the heavens. Williams leads the effort to apply the same technology to human vision.
The adaptive optics technique allows researchers to study the retina in ways that were never before possible. Being able to peer into the eye of a living patient affords a researcher to ask simple questions, like the most basic in this case—“Are you colorblind?” Many diseases degenerate the cells of the retina, and since donated tissue does not have a medical history attached, it’s very difficult to know whether a sample of tissue came from a colorblind individual or someone suffering from another malady.
The ability to work with live patients also gives the researchers access to further tests of their overall health, including behavioral and genetic tests which can help determine what kind of disease may be causing damage to their retina.