Press release
Thursday, March 11, 2021
By removing foreign light, scientists improved the resolution by 33%.
A team led by scientists from the National Eye Institute (NEI) non-invasively visualized the light-detecting cells in the back of the eye, known as photoreceptors, in more detail than ever before. Published in Optics, the researchers report how they improved imaging resolution by a third by selectively blocking the light used to imagine the eye. NEI is part of the National Institutes of Health.
The achievement is the latest in an evolving strategy to monitor cellular changes in retinal tissue that, in turn, will help identify new ways to treat and prevent vision loss caused by diseases such as age-related macular degeneration. main cause of blindness in humans. Over 65 years.
Better image resolution will allow better tracking of degenerative changes that occur in retinal tissue. The aim of our research is to discern changes related to the disease at the cellular level over time, allowing possible detection of the disease much earlier, “said the study’s lead researcher, Johnny Tam, Ph.D., Stadtman Investigator in the Clinical and Translational Imaging Unit at NEI.
Early detection would make it possible to treat patients earlier, long before they lose their sight. Moreover, the detection of cellular changes would allow clinicians to determine more quickly whether a new therapy is working.
The two types of photoreceptors, cones, which allow color vision, and rods, which allow low light vision, vary in size and density throughout the retina. Conical photoreceptors, although larger than rods, are more difficult to visualize when closer together because they are in the fovea, the region of the retina responsible for the highest level of visual acuity and color discrimination. The whole landscape of cones and rods is called a photoreceptor mosaic.
Advanced imaging systems are widely used to observe retinal tissue and are essential tools for diagnosing and studying retinal diseases. But even with retinal imaging of adaptive optics, a technique that compensates for light distortions using deformable mirrors and computer-driven algorithms, there are still some areas of the photoreceptor mosaic that are challenging for the image, according to the first author, Rongwen Lu, Ph.D. ., postdoctoral fellow in the Clinical and Translational Imaging Unit at NEI.
“Sometimes the rods are hard to imagine because they are so small,” Lu said. “By removing some of the light from the system, it’s actually easier to see the rods. So in this case, less is more. ”
In this latest report, Tam’s team at NEI, with the help of researchers at Stanford University in Palo Alto, California, tried to push the adaptive optical resolution of the retinal image, strategically blocking some of the light to imagine the retina.
By blocking the light that illuminates the eye in the middle of the beam, to create a ring of light (rather than a disk), the NEI-led team improved the transverse resolution (over the mosaic). But this came at the expense of axial resolution (mosaic depth). To compensate, Tam’s team blocked the light coming back from the eyes using a super small hole, called a sub-airy disk, which recovers the axial resolution that would have been lost using the light ring alone.
Combining ring illumination with the image on the sub-airy disc results in the best of both worlds, Tam said. The modified technique produces an increase of about 33% in resolution, which makes it much easier to see the rods, as well as the subcellular details in the cones.
Their technique has also improved the visualization of the photoreceptor mosaic with another technique called non-confocal split-detection, which is yet another type of microscopy that provides a complementary view of the photoreceptor mosaic.
The work was partially supported by NEI grants U01 EY025477 and R01 EY025231 and by the Intramural Research Program from NEI, part of the National Institutes of Health.
NEI conducts federal government research on the visual system and eye diseases. NEI supports basic science and clinical programs to develop vision-saving treatments and to meet the special needs of people with vision loss. For more information, visit https://www.nei.nih.gov.
About the National Institutes of Health (NIH):
NIH, the national medical research agency, includes 27 institutes and centers and is a component of the US Department of Health and Human Services. NIH is the leading federal agency that conducts and supports basic, clinical, and translational medical research and investigates the causes, treatments, and cures of both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.
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References:
Lu R, Aguilera N, Liu T, Liu J, Giannini JP, Li J, Bower AJ, Dubra A, Tam J. “Adaptive in vivo adaptive optical imaging of photoreceptors in the human eye with annular pupil illumination and sub-aeration detection ”, published on March 11, 2021, Optics. https://doi.org/10.1364/OPTICA.414206