A new imaging approach could help accelerate the development of new treatments for eye diseases

A new imaging approach could help accelerate the development of new treatments for eye diseases

Researchers have developed a simple and rapid method for performing optoretinography, an imaging technique that measures light-induced functional activity in the eye's retina, the network of neurons at the back of the eye that is responsible for detecting light and initiating vision. Retinal diseases such as macular degeneration and diabetic retinopathy affect more than 50 percent of people in the United States over the age of 60. These diseases affect the function of the retina in a way that reduces vision and, if left untreated, can lead to blindness. The new approach could help accelerate the development of new treatments for eye diseases.

Optoretinography has typically used very expensive equipment that required multiple experts to operate, while at the same time producing enormous amounts of data that required extensive computing resources. We found a way to make it cheaper and faster.”

Ravi Jonnal, research team leader, University of California, Davis

Jonnal and colleagues report their new approach, which they call velocity-based optoretinography, in Optica, the Optica Publishing Group's journal of high-impact research. They also demonstrate the method's ability to measure retinal response in three healthy volunteers.

"Although velocity-based optoretinography could potentially provide clinicians with more accurate and earlier information about loss of function in the retina, its first real impact is more likely to be in accelerating clinical trials for new treatments for retinal diseases," said Jonnal, who performed some of the first optoretinographic measurements as a graduate student in Don Miller's laboratory at Indiana University. “If we can see whether retinal function is improving or deteriorating more quickly than with traditional tests such as eye charts, this will significantly accelerate the development of treatments.”

Tracking shape changes

Optoretinography detects subtle changes in the shape of neurons that produce or transmit 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 living, moving eye, then applied motion correction algorithms to stabilize the images and extract the functional response. This costly and time-consuming process requires resolving and tracking the location of individual cell features and using those locations to determine whether the cell has changed shape.

“If we use one of our adaptive optics systems to perform optoretinographic measurements, the experiment can easily take half a day and result in a terabyte of data to process,” Jonnal said. “Processing the data to extract a functional signal will take at least another day or two.”

To avoid the need to resolve and track individual neurons, Jonnal and colleagues wanted to see if they could instead measure the speed, or rate, at which the retina's neurons move relative to one another. “We believed that even if the locations of the features varied from cell to cell, the speed at which they moved relative to each other would be highly correlated between cells,” Jonnal said. “That turned out to be true.”

Measuring moving neurons

To perform velocity-based optoretinography, researchers developed a new OCT camera that allows a single operator to capture images from more locations in the retina than is possible with other optoretinography approaches.

The researchers demonstrated their new technique by collecting measurements from three healthy volunteers. They were able to collect data from each patient in just ten minutes and process that data and make results available within 2 to 3 minutes. They showed that the functional optoretinographic responses measured with the simple approach scaled with the light stimulus dose used and that the dose-stimulus response was reproducible within and between volunteers.

They are now planning experiments aimed at demonstrating the technique's sensitivity to disease-related dysfunction. Jonnal is also working with doctors at the University of California, Davis, to use it for patient imaging and to help interpret results for 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 diseases.

Source:

optics

Reference:

Vienola, KV, et al. (2022) Velocity-based optoretinography for clinical applications. Optics. doi.org/10.1364/OPTICA.460835.

.