Researchers at the Duke Eye Center in the United States have made an important – and surprising – discovery in human eye anatomy that has gone unnoticed for decades.
A media release said that the researchers, using enhanced imaging technology, identified a previously unknown part of photoreceptor cells in the retina.
Their finding, published in Communications Biology, challenges long-standing assumptions about the retina and opens new avenues for understanding vision and genetic eye diseases, the release said.
Most of what researchers know about retinal anatomy has come from exhaustive studies using electron microscopy in the 1960s and 1970s. Eventually, no new major discoveries were being made in the anatomy of the retina, so that chapter of research closed.
But technology kept advancing, says the release.
Oleg Alekseev, MD, PhD, assistant professor of ophthalmology, and Vadim Arshavsky, PhD, Helena Rubinstein Foundation Distinguished Professor of Ophthalmology, decided to use three-dimensional electron tomography, which creates a 3D map of an object, to look at retinas with unprecedented resolution.
“We aimed to take a look at some very small structures,” Assistant Prof Alekseev said, “but we found something pretty major.”
Inside the retina are photoreceptor cells, commonly known as rods and cones. Photoreceptor cells convert light signals into electrical messages that the brain decodes and processes into visual images. Assistant Prof Alekseev, Prof Arshavsky, and the team in Durham, North Carolina found that each rod photoreceptor cell contains a large, mechanically reinforced protrusion, which they’ve termed the accessory inner segment (aIS).
“The function isn’t known yet,” Assistant Prof Alekseev said, “but we presume it serves as a physical support to hold the photoreceptor.”
Photoreceptors are long and narrow. The researchers think that the aIS holds everything together and stable, preventing the photoreceptors from collapsing and flopping.
“We need to explore this structure further,” Assistant Prof Alekseev said. “It’s very likely that some diseases are caused by defects in the aIS, and now we have the opportunity to explore those diseases, improve our ability to diagnose patients, and start thinking about treatments.”
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