Researchers have developed a quick and easy way to perform optoretinography, an imaging technique that measures light-induced functional activity in the eye’s retina, the neural network at the back of our eyes. eyes responsible for detecting light and initiating vision. More than 50% of people over the age of 60 in the United States are affected by retinal diseases such as macular degeneration and diabetic retinopathy. These diseases affect the function of the retina in such a way as to reduce sight and can progress to blindness if left untreated. The new approach could help speed the development of new treatments for eye diseases.
“Optoretinography has typically used very expensive equipment that required multiple experts to operate while producing huge volumes of data requiring extensive computational resources,” said research team leader Ravi Jonnal from the University. from California to Davis. “We figured out a way to do it in a more economical and original way.”
Jonnal and colleagues report their new approach, which they call velocity-based optoretinography in Optical, Optica Publishing Group’s journal for high-impact research. They also demonstrate the ability of the method to measure the retinal response in three healthy subjects.
“While velocity-based optoretinography has the potential to provide clinicians with more accurate and earlier insights into retinal functional losses, its first real impact is more likely to be the acceleration of clinical trials for new treatments. retinal disease,” said Jonnal, who performed some of the first optoretinographic measurements as a doctoral student in Don Miller’s lab at Indiana University. “If we can detect whether retinal function is improving or deteriorating faster than with traditional tests such as eye charts, it will dramatically speed up the development of treatments.”
Shape Change Tracking
Optoretinography detects slight changes in the shape of neurons that generate or conduct signals in the retina. So far, Jonnal and other researchers have used adaptive optics and optical coherence tomography (OCT) to visualize and track these neurons in the moving live eye, then applied motion correction algorithms to stabilize the images and extract the functional response. This expensive and time-consuming process requires resolving and tracking the position of individual cell features and using these positions to determine if the cell has changed shape.
“When we use one of our adaptive optics systems to perform optoretinography measurements, the experiment can easily take half a day and result in a terabyte of data to process,” Jonnal said. “Data processing to extract a working signal takes, at a minimum, a day or two longer.”
To avoid having to resolve and track individual neurons, Jonnal and his colleagues wanted to see if they could instead measure the speed, or velocity, at which retinal neurons move relative to each other. “We thought that even though the positions of features vary from cell to cell, the speed at which they move relative to each other would be highly correlated between cells,” Jonnal said. “It turned out to be correct.”
Measuring neurons in motion
To perform velocity-based optoretinography, researchers have developed a new OCT camera that allows a single operator to collect images from more locations in the retina than is possible with other approaches to imaging. optoretinography.
The researchers demonstrated their new technique by using it to collect measurements from three healthy volunteers. They were able to acquire each patient’s data in just ten minutes and have that data processed and get the results in 2-3 minutes. They showed that the functional optoretinographic responses measured with the simple approach changed with the dose of light stimulus used and that the dose-stimulus response was reproducible in and between volunteers.
They are now planning experiments to demonstrate the technique’s sensitivity to disease-related dysfunctions. Jonnal also works with clinicians at the University of California, Davis to use it for patient imaging and to help interpret results from trials of stem cell therapies and gene therapy treatments for inherited retinal diseases. The researchers would also like to apply the new optoretinography approach to animal models of retinal disease.