NEI Sets Sights on Better Retinal Imaging

NEI scientists have noninvasively visualized the light-sensing cells in the back of the eye, known as photoreceptors, in greater detail than ever before. The researchers improved imaging resolution by 33 percent by eliminating extraneous light. The results were published in Optica.

“Better imaging resolution will enable better tracking of degenerative changes that occur in retinal tissue,” said Dr. Johnny Tam, Stadtman Investigator in NEI’s clinical and translational imaging unit. “The goal of our research is to discern disease-related changes at the cellular level over time, possibly enabling much earlier detection of disease.”

Earlier detection would make it possible to treat patients sooner, well before they’ve lost vision. And by detecting cellular changes, clinicians could more quickly determine whether a new therapy is working.

The two types of photoreceptors—cones (color vision) and rods (low-light vision)—vary in size and density across the retina. Cone photoreceptors, while larger than rods, are trickier to visualize when they’re more tightly packed together as they are in the fovea, the region of the retina responsible for the highest level of visual acuity and color discrimination.

Tam’s team at NEI, with help from researchers at Stanford University, sought to push the resolution of adaptive optics retinal imaging. 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 (across the photoreceptor mosaic). But that came at the expense of axial resolution (mosaic depth). To compensate, Tam’s team blocked the light coming back from the eye using a pinhole called a sub-Airy disk, which recovers the axial resolution that would have been lost.

Combining the ring illumination with the sub-Airy disk imaging results makes it much easier to see rods, as well as subcellular details within cones. 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 from diseases such as age-related macular degeneration, a leading cause of blindness in people age 65 and older.