The NIH-led team is raising the bar for retinal imaging

News release

Thursday, March 11, 2021

By eliminating extraneous light, the scientists improved the resolution by 33%.

A team led by scientists from the National Eye Institute (NEI) has visualized the light-sensitive 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 image resolution by a third by selectively blocking the light used to image the eye. NEI is part of the National Institutes of Health.

The feat is the latest in an evolving strategy to monitor cell changes in retinal tissue, which will in turn help identify new ways to treat and prevent vision loss from diseases such as age-related macular degeneration, a leading cause of blindness in humans . 65 and older.

“Better image resolution will make it possible to better monitor degenerative changes occurring in the retinal tissue. The aim of our study is to discover disease-related changes at the cellular level over time, which could potentially detect disease much earlier, ”said study lead investigator Johnny Tam, Ph.D., Stadtman researcher in clinical and translational imaging. Unit at NEI.

Earlier detection would allow patients to be treated earlier, well before they have lost vision. In addition, by detecting cellular changes, clinicians could more quickly determine whether a new therapy is working.

The two types of photoreceptors, cones, which enable color perception, and rods, which enable low-light vision, vary in size and density across the retina. Cone-shaped photoreceptors, although larger than rods, are more difficult to visualize when packed closer together, as they are located in the fovea, the area of ​​the retina responsible for the highest level of visual acuity and color discrimination. The whole landscape of cones and rods is called the photoreceptor mosaic.

Advanced imaging systems are widely used for observing retinal tissue and are essential tools for diagnosing and studying retinal disease. But even with adaptive optics retinal imaging, a technique that compensates for light distortions using deformable mirrors and computer-aided algorithms, there are still some areas of the photoreceptor mosaic that are challenging to image, said the paper’s lead author, Rongwen. Lu. , Ph.D., a postdoctoral fellow in the Clinical and Translational Imaging Unit at NEI.

“Sometimes bars are hard to imagine because they are so small,” said Lu. “Eliminating some of the light in the system actually makes it easier to see the rods. So in this case, less is more. “

In this latest report, Tam’s team at NEI, with help from researchers at Stanford University, Palo Alto, California, sought to further improve the resolution of adaptive optical retinal imaging by strategically blocking some of the light to image the retina.

By blocking the light illuminating the eye in the center of the beam to create a ring of light (instead of a disk), the team led by NEI improved the transverse resolution (across the mosaic). But that was at the expense of axial resolution (mosaic depth). To compensate for this, Tam’s team blocked the light coming back from the eye using a super small hole called a sub-Airy disk, which restores the axial resolution that would have been lost with just the ring of light.

The combination of the ring illumination with the sub-Airy disk imaging results in the best of both worlds, Tam said. The pinched technique yields approximately 33% resolution, making it much easier to see rods as well as subcellular detail in cones.

Their technique 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 supported in part by NEI grants U01 EY025477 and R01 EY025231, and by the NEI’s intramural research program, part of the National Institutes of Health.

NEI is leading the federal government’s investigation of the visual system and eye diseases. NEI supports basic and clinical science programs to develop vision reduction treatments and meet the special needs of people with vision loss. Visit https://www.nei.nih.gov for more information.

About the National Institutes of Health (NIH):
NIH, the national medical research agency, includes 27 institutes and centers and is part of the United States Department of Health and Human Services. NIH is the premier federal agency that conducts and supports basic, clinical, and translational medical research, investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

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