Adaptive optics technology increases image quality by using an optical component called a wavefront sensor to detect light distortion caused by the eye. A deformable mirror that quickly changes shape is then used to compensate for the detected light distortion, leading to clearer images.
To shrink the components within an AOSLO, the researchers developed a new algorithm to perform wavefront sensing. “Other researchers have shown that the wavefront sensor can be replaced by an algorithm, but these algorithms haven’t been fast enough to be used in a hand-held device,” said Farsiu. “The algorithm we developed is much faster than previously used techniques and just as accurate.”
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The researchers also incorporated a commercially available MEMS-based deformable mirror measuring just 10.5 millimeters in diameter. “The optical and mechanical design combined with our new algorithm made it possible to create the handheld device,” said Duke optics expert and team member Joseph Izatt. “Adaptive optics systems are very sensitive to slight vibrations or motions, but we designed our system to be very stable. The optics stay aligned when the system is transported, and it can also compensate for hand motions during use.”
Imaging in people
They used their new system, called HAOSLO for hand-held AOSLO, to image the retinas of 12 healthy adult volunteers and two children under anesthesia. The application of the system on a 31-month-old child represents the first use of adaptive optics to image photoreceptors in children.
Photoreceptors in adult eyes gradually become smaller toward an area at the center of the retina known as the fovea. The HAOSLO system was able to image photoreceptors as close as 1.4 degrees eccentric to the fovea, where photoreceptors have an average spacing of only 4.5 microns. The closest that had been accomplished without adaptive optics was 3.9 degrees. Before starting large-scale clinical trials with the instrument, the researchers plan to incorporate additional imaging modalities useful for detecting disease.
To help other scientists adapt their system for specific applications, the researchers made the optical and mechanical designs, computational algorithms and control software for the new HAOSLO system available online free of cost.
Optica is an open-access, online-only journal dedicated to the rapid dissemination of high-impact peer-reviewed research across the entire spectrum of optics and photonics. Published monthly by The Optical Society (OSA), Optica provides a forum for pioneering research to be swiftly accessed by the international community, whether that research is theoretical or experimental, fundamental or applied. Optica maintains a distinguished editorial board of more than 50 associate editors from around the world and is overseen by Editor-in-Chief Alex Gaeta, Columbia University, USA.