NIH-led team sets new benchmark for retinal imaging

News Release

Thursday 11 March 2021

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

A team led by scientists from the National Eye Institute (NEI) has visualized the light-sensing cells at the back of the eye, known as photoreceptors, more intrusively than ever before. Published in Optica, the researchers report how they improved the 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 achievement is the latest in an evolving strategy to monitor cell changes in retinal tissue that in turn will help identify new ways to treat and prevent vision loss due to diseases such as age-related macular degeneration, a leading cause of blindness in people. 65 and older.

” A better image resolution will detect better degenerative changes in retinal tissue. The aim of our research is to discern disease-related changes at the cellular level over time, possibly enabling disease detection much earlier, “said research leader Johnny Tam, Ph.D., Stadtman Investigator in Clinical and Translational Imaging. Unit at NEI.

Earlier detection would make it possible to treat patients earlier, even before they have lost their sight. What’s more, detecting cellular changes can enable clinicians to more quickly determine if a new therapy is working.

The two types of photoreceptors, cones that allow color vision, and rods that allow vision in low light, vary in size and density across the retina. Cone photoreceptors, although larger than sticks, are more difficult to visualize if they are tightly packed together as in the fovea, the area of ​​the retina that is 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 the observation of retinal tissue and are essential tools for the diagnosis and study of retinal diseases. But even with adaptive optical retinal imaging, a technique that compensates for light distortion using distortable mirrors and computer-driven algorithms, according to the first author of the article, Rongwen Lu, there are still some areas of photoreceptor mosaic that are challenging for the image. , Ph.D., a postdoctoral fellow in the clinical and translation unit at NEI.

“Sometimes it’s hard to picture sticks because they’re so small,” Lu said. ‘By turning off the light in the system, it becomes easier to see the bars. In this case, less is therefore more. ”

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

By blocking the light that illuminates the eye in the center of the beam, to create a ring of light (instead of a disk), the NEI-guided team improved the transverse solution (across the mosaic). But it comes at the expense of the axial resolution (mosaic depth). To compensate, Tam’s team blocked the light returning through the eye through a super small hole called a sub-Airy disk, which restores the axial resolution that would be lost with the light ring alone.

Tam said the ring lighting is combined with the sub-Airy disc imagery. The adaptive technique yields an increase of about 33% in resolution, making it much easier to see sticks, as well as subcellular details within cones.

Their technique also improves 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 image of the photoreceptor mosaic.

The work was supported in part by NEI grants U01 EY025477 and R01 EY025231, and by the Intramural Research Program at NEI, part of the National Institutes of Health.

NEI leads the federal government’s research on the visual system and eye diseases. NEI supports basic and clinical science programs to develop vision-saving treatments and address 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 country’s medical research agency, contains 27 institutes and centers and is part of the U.S. Department of Health and Human Services. NIH is the primary federal agency that conducts and supports basic, clinical, and translational medical research, investigating the causes, treatments, and drugs for common and rare diseases. Visit www.nih.gov for more information on NIH and its programs.

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