Press release
Thursday, March 11, 2021
By eliminating the strange light, the scientists improved the resolution by 33%.
A team led by scientists at the National Eye Institute (NEI) visualized non-invasively the light-sensitive cells in the back of the eye, known as photoreceptors, in more detail than ever. Published in Optica, the researchers report how they improved the image resolution by one third, selectively blocking the light used for the eye image. 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 from diseases such as age-related macular degeneration, one of main causes of blindness in people aged 65 and older.
“A better resolution of the image will allow a better tracking of the degenerative changes that occur in the retinal tissue. The goal of our research is to discern disease-related changes at the cellular level over time, possibly allowing for much earlier detection of the disease, ”said study lead investigator Johnny Tam, Ph.D., Stadtman Imaging Investigator Clinical and Translational Unit of the NIS.
Early detection would make it possible to treat patients earlier, well before they lose their sight. In addition, detecting cellular changes would allow doctors to more quickly determine whether a new therapy is working.
The two types of photoreceptors, cones, which allow vision in color, and rods, which allow vision in the dark, vary in size and density in the retina. Conical photoreceptors, although larger than rods, are more difficult to see when they are more compacted than in the fovea, the region of the retina responsible for the highest level of visual acuity and color discrimination. The entire 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 diseases of the retina. But even with the retinal image with adaptive optics, a technique that compensates for light distortions using deformable mirrors and computer-controlled algorithms, there are still some areas of the photoreceptor mosaic that are challenging for the image, according to the first author of the article, Rongwen Lu, Ph.D., a postdoctoral fellow at the NEI Clinical and Translational Imaging Unit.
“Sometimes the stems are difficult to imagine because they are very small,” said Lu. “By eliminating some of the light from the system, it is really easier to see the rods. So in this case, less is more. “
In this latest report, the NEI Tam team, with the help of researchers at Stanford University, Palo Alto, California, sought to increase the resolution of the retinal image with adaptive optics by strategically blocking part of the light to obtain the retinal image.
By blocking the light that illuminates the eye in the middle of the beam, to create a ring of light (instead of a disc), the NEI-led team improved the cross-sectional resolution (through the mosaic). But this occurred at the expense of axial resolution (depth of the mosaic). To compensate, Tam’s team blocked the light coming back from the eye using a super small hole, called a sub-Airy disk, which recovers the axial resolution that would have been lost only with the ring of light.
Combining the lighting of the ring with the image of the sub-Airy disk results in the best of both worlds, said Tam. subcellular details inside the cones.
The technique also improved the visualization of the photoreceptor mosaic with another technique called non-confocal division detection, which is another type of microscopy that provides a complementary view of the photoreceptor mosaic.
The work was supported in part by grants from NEI U01 EY025477 and R01 EY025231, and by the NEI Intramural Research Program, part of the National Institutes of Health.
The NEI leads the federal government’s research on the visual system and eye diseases. The NEI supports basic and clinical science programs to develop vision-saving treatments and 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 country’s medical research agency, includes 27 institutes and centers and is a component of the United States Department of Health and Human Services. The NIH is the leading federal agency that conducts and supports basic, clinical and translational medical research, and is investigating the causes, treatments and cures for 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. aerial detection ”, published on March 11, 2021, Optica. https://doi.org/10.1364/OPTICA.414206