Stargazing Technique to See Inside the Human Eye
Stars twinkle in the sky, but did you know that the twinkling effect of the stars you see during stargazing is due to the distortions in the atmosphere such as turbulence and wind shear? We enjoy watching the twinkling stars, but the same does not hold true for people who study distant galaxies.
Human eyes too, have their own “twinkling problem” which the eye doctors come across when they try to look deep into our eyes, distortions within the cornea and lens impair light as it travels through the eyeball, frustrating their efforts. Lately, a solution has been developed to overcome this problem which is called “adaptive optics” pioneered by astronomers and originally developed by the military and used by astronomers such as Scot Olivier at California’s Lawrence Livermore National Laboratory to produce clear images of faraway stars.The same technique when used to view human eye allows researchers to view minute details of our eyes and even lets them diagnose blinding disease like macular degeneration months before existing technology can detect.
What is Adaptive Optics?
In astronomy, adaptive optics uses a device known as a wave-front sensor to detect the degree to which light has been distorted as it approaches the telescope.
However, it was only in the 1990s that University of Rochester vision scientist David Williams had his eureka moment: Why not apply the techniques of adaptive optics to imaging the human eye to be able to produce clearer images of the retina? With the human eye, Williams realised, scientists could shine a laser—that’s about one million times weaker onto the back of the retina, which functions as a weak mirror. That light spot is then used to measure and adjust for the imperfections in the focusing optics of the eye, Olivier says.
Williams started working on it, and along with the collaborators, they developed a system to produce the first images of the three types of cone photoreceptors responsible for colour vision in a study in Nature in 1999. Taking this as a stepping stone, Olivier joined forces with John Werner, a UC Davis vision researcher and Donald Miller, a scientist at the Indiana University to develop a more advanced prototype.
Adaptive optics is tremendous for minute details, but it produces only 2D images. So the group combined it with another technique called optical coherence topography, used to measure the thickness of tissues like the retina. The result: the ability to produce 3D images of cells within the retina, such as cone photoreceptors, which isn’t possible with any other technology, Olivier says.
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