New optoretinography technique allows direct measurement of rod function in vivo

A press release from the University of Washington, Seattle, reported what they described as a future diagnostic tool to view how the ocular molecules work.

“Researchers have validated an approach to measure how rod photoreceptors, the cells in our eyes responsible for night vision, respond to light in living eyes,” the investigators said. They reported the results using their technology in Light: Science & Applications.¹

According to corresponding author Ram Sabesan, PhD, who was quoted in the press release, "This is the first time we've been able to see this happen in rod cells in a living eye." He is an associate professor of ophthalmology at the University of Washington School of Medicine.

Importantly, the investigators explained that because dysfunction of the rods is one of the earliest signs of many retinal diseases, including age-related macular degeneration and retinitis pigmentosa, direct monitoring of the rods’ response may facilitate both early disease detection and monitoring of responses to treatment.

The investigators used a technology called optoretinography (ORG) that made this visualization possible. ORG is an emerging technology used to test light-evoked photoreceptor activity, they explained.

ORG, they pointed out, incorporates both adaptive optics, which allows the rods to be differentiated from the cones in the eye, and interferometry, which allows the investigators to measure minute distances and surface irregularities with precision.

In their study, they measured the in vivo responses of both rat and human rod cells and found that both “showed minute contractions of the rods’ outer segments that occurred within 10 milliseconds of light exposure.”

The first step in the responses is the activation of rhodopsin. Rhodopsin is a protein in the retina that is sensitive to light, and its activation is the first step in visual phototransduction in the retina.

Because of the ability of ORG to detect these contractions, the technology can surpass conventional diagnostic methods in identifying and measuring cellular structures. As a result, senior author Tong Ling, PhD, explained that ophthalmologists can distinguish and measure cellular structures with higher spatial resolution and noninvasively. He is from the School of Chemistry, Chemical Engineering, and Biotechnology, Nanyang Technological University, and the Singapore Eye Research Institute, Singapore National Eye Centre, both in Singapore.

The investigators explained, “The [current] in vivo techniques are limited in their sensitivity, specificity, and cellular resolution, while the ex vivo approaches are invasive to be used in living eyes. An ideal measure of rod viability would inform us of both its structural and functional integrity with high sensitivity and resolution.”¹

In addition, the currently used diagnostics take significant time and can be burdensome for patients.

“The non-invasive in vivo optical imaging of rhodopsin activation extends the diagnostic capability of ORG and may facilitate personalized, objective assessment of rod dysfunction and visual cycle impairment in inherited and age-related macular degeneration,” the authors concluded.

Reference

1. Li H, Weiss CE, Pandiyan VP, et al. Optoretinography reveals rapid rod photoreceptor movement upon rhodopsin activation. Light Sci Appl. Applications 2026;15:58; https://doi.org/10.1038/s41377-025-02149-6