Vision scientists uncover reasons behind unusual perceptual properties of the eye’s fovea

Vision scientists have uncovered some of the reasons behind the unusual perceptual properties of the eye’s fovea. Only humans and other primates have this dimple-like structure in their retinas. It is responsible for visual experiences that are rich in colorful spatial detail.
Figuring out how the fovea functions is essential to the search for strategies to correct central vision loss, including efforts to design visual prosthetics.
“Diseases such as macular degeneration are much more debilitating than deficits in peripheral eyesight because of the importance of the fovea to everyday vision,” said Dr. Raunak Sinha of the Department of Physiology and Biophysics at the University of Washington School of Medicine.
The fovea is a specialized region that dominates our visual perception, Sinha explained. It provides more than half of the input from the eyes to the visual cortex of the brain.
When you look at a scene an arm’s length away, he said, the fovea subtends a field only about the size of your thumbnail. Your eyes undergo rapid movements to direct the fovea to various parts of the scene.
The absence of a fovea in most mammals, he said, and technical challenges associated with recording from the primate fovea, led to a paucity of information about how the fovea operates at the level of cellular circuits.
Using advanced techniques, Sinha helped lead a study that revealed that the computational architecture and basic visual processing of the fovea are distinct from other regions of the retina. The results help explain why central and peripheral vision have different qualities, he said. Located near the optic nerve, the fovea is at its best for fine tasks like reading. Compared to the peripheral retina, however, the fovea is less able to process rapidly changing visual signals…..
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Source: News Medical