Researchers have developed a simple and fast way to perform optical imaging, an imaging technology that measures light-induced functional activity in the retina, the network of neurons at the back of our eyes responsible for detecting light and initiating vision. More than 50 percent of people in the United States over the age of 60 suffer from retinal diseases such as macular degeneration and diabetic retinopathy. These diseases affect the function of the retina in ways that reduce vision and can progress to blindness if not treated. The new approach could help accelerate the development of new treatments for eye diseases.
Optical mapping typically uses very expensive equipment that requires many experts to work while producing huge amounts of data that require extensive computational resources. We’ve come up with a way to do it cheaper and more exotic.”
Ravi Gunal, Research Team Leader, University of California, Davis
Gunal and colleagues report their new approach, which they call velocity-based optical imaging opticsOptica Publishing Group for high-impact research. They also demonstrate the method’s ability to measure retinal response in three healthy subjects.
said Junal, who made one of the first optics and artery measurements as a doctoral student in Don Miller’s lab at Indiana University. “If we can detect whether retinal function is getting better or worse faster than traditional tests like eye charts, it will greatly speed up the development of treatments.”
Track Shape Changes
Optical retinal imaging reveals subtle changes in the shape of the nerve cells that generate or transmit signals in the retina. So far, Gunal and other researchers have used adaptive optics and optical coherence tomography (OCT) to visualize and track these neurons in the living and moving eye and then applied motion correction algorithms to image stabilization and functional response extraction. This expensive and time-consuming process requires resolving and tracking the position of individual cellular features and using these positions to determine whether or not the cell has changed its shape.
“When we use one of our adaptive optics systems to perform retinal optics measurements, the experiment can easily take half a day and result in terabytes of data to process,” Gunal said. “It takes at least another day or two to process the data to extract a functional signal.”
To avoid the need to resolve and track individual neurons, Gunal and his colleagues wanted to see if they could instead measure the speed or speed at which retinal neurons are moving relative to each other. “We thought that even if the positions of the features differed from cell to cell, the speed at which they moved relative to each other would be highly correlated between cells,” Gunal said. “This has been proven to be true.”
Measurement of moving neurons
To perform a velocity-based optical retinal mapping, researchers have developed a new OCT camera that allows a single operator to collect images from more sites in the retina than is possible with other methods of optical retinal mapping.
The researchers demonstrated their new method by using them to collect measurements from three healthy volunteers. They were able to obtain data from each patient in just ten minutes and process that data and available results within 2 to 3 minutes. They showed that functional responses to retinal optics measured by the simple approach measured by the dose of photostimulus used and that the dose-stimulus response was reproducible within and between volunteers.
They are now planning experiments aimed at demonstrating the technology’s sensitivity to disease-related dysfunction. Gunal is also working with physicians at the University of California, Davis for use in patient imaging and to help interpret results from trials of stem cell and gene therapies for hereditary retinal diseases. The researchers would also like to apply the new retinal optics approach to animal models of retinal diseases.
Vienola, KV, et al. (2022) Velocity-based optical imaging for clinical applications. optics. doi.org/10.1364/OPTICA.460835.