Click For Photo: https://www.sciencedaily.com/images/2019/03/190321092246_1_540x360.jpg
"Studying cells of the retinal pigment epithelium in the clinic is like looking into a black box. RPE cells are difficult to see, and by the time signs of disease are detectable with conventional techniques, a lot of damage has often already occurred," said Johnny Tam, Ph.D., the lead author of the study. "This study is proof-of-concept that we can use a fluorescent dye to reveal this unique fingerprint of the RPE, and to monitor the tissue over time."
The RPE is a cell layer that lies next to and maintains the health of the retina's light-sensing photoreceptors. Because the cells contain pigment, and thus absorb incoming light, the thin layer of RPE tissue is difficult to image. Even using adaptive optics, a specialized imaging technology that can distinguish individual cells in the eye, Tam and colleagues found visualizing the RPE layer challenging.
Tam - Fluorescent - Dye - Indocyanine - Green
So, Tam turned to an FDA-approved fluorescent dye called indocyanine green (ICG) that is used to visualize the blood vessels in the back of the eye. While the dye fades from the blood vessels quickly, within about thirty minutes, the dye persists in the RPE for several hours, revealing a fluorescent mosaic pattern, with some cells appearing more brightly and others more dimly.
"Initially, we didn't know how the dye was going to look," said Tam. "We put the dye in and we got this pattern that at first looked kind of random. It was a big surprise that we could come back after a year, re-inject the dye, and see the same pattern."
Tam - Colleagues - Software - RPE - Patterns
Tam and colleagues designed software that recognizes RPE patterns and then computes changes that occur from one imaging session to the next. For healthy volunteers, there was very little change in the RPE over several months, with the vast majority of the cells retaining...
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