Seeing through a new lens

The old saying "seeing is believing" holds true for much of scientific research. As visual beings, the better we can see something, the better chance that we have of understanding how it works and how to fix it when it's broken. \nWhen researchers apply technology that astronomers use to filter out atmospheric distortions to seeing individual cells in the back of the human eye, seeing is not only believing, but it may lead to better vision.\nDonald Miller and Larry Thibos, professors in the IU School of Optometry, are working on this application of adaptive optics technology to get more accurate pictures of the human eye. Their combined instrumentation, one of only five systems of its kind in the world, currently allows them to see the human retina at a resolution of a few microns, one-hundredth of the size of a pencil lead.\n"If we can start to see cells on the back of the eye, we can diagnose disease at an earlier state," Miller said. "We can monitor treatment and make treatment more effective." \nThe instrumentation is not yet approved for diagnostic use, but Miller and Thibos both predict it will be available within the next five years. \nOne of the target diseases is glaucoma, where slow degeneration of the cells eventually leads to vision loss. But often by the time a patient notices problems, the damage is already done. \n"The main obstacle to a clinician seeing what's wrong with your retina is that your optical system is imperfect," Thibos said. "So we try to look in there and it's all fuzzy." \nTheir approach to getting clear images on the retina is to first measure the aberrations in the eye, using an ocular aberrometer developed in Thibos' laboratory, according to an IU press release. However, the aberrations in the eye are constantly changing.\n"It's all changing because your tear film is evaporating and the lens inside your eye is changing its size and its shape," Thibos said. \nMiller then uses adaptive optics technology that both responds to the detected aberrations and then corrects for them at speeds of approximately 10 times per second. Although widely used by astronomers, adaptive optics is a new technique in vision science.\nThe instrumentation is also much smaller than a telescope in a large observatory. The centerpiece of Miller's lab is a 5 ft. by 8 ft. table, with precisely positioned lenses and mirrors carefully screwed into place. A cabinet nearby held a collection of specific dental imprints that subjects bite down on to keep their heads still while the instrument takes measurements. \nMiller showed impressive images comparing a normal image of a photoreceptor, a cell on the retina that converts light to an electrical signal that is sent to the brain. The uncorrected image looked like a broad, white streak on a gray canvas, compared with a clear white dot on the corrected image.\nThe two greatest challenges in making this technology generally available are the physical size and the expense of the instrumentation. Efforts to commercialize the technology using cheaper components are currently underway. The measurements are done below safe optical limits. \nThibos sees a broad impact of adaptive optics technology on optometry in general. \n"Everything that we've learned so far has always been limited by this crummy optical system in the front of our eye," Thibos said. "We can learn to what extent do we have blinkers on as vision scientists."\nSo, as the technology that leads to clear pictures of stars moves toward a mainstream eye test, our generation may have more tools to diagnose potential vision problems before they become serious. And seeing really will be believing.