Researchers have developed visual simulations that indicate what the world might look like to people with retinal implants, suggesting the patients may see fuzzy, comet-like shapes or blurred outlines.
A study by University of Washington concludes that while important advancements have been made in the field, the vision provided by sight recovery technologies may be very different from what scientists and patients had previously assumed.
Researchers used simulations to create short videos that mimic what vision would be like after two different types of sight recovery therapies.
"This is the first visual simulation of restored sight in any realistic form," said lead author Ione Fine, a UW associate professor of psychology.
Fine said the research aims to provide information about the quality of vision people can expect if they undergo sight restoration surgery, an invasive and costly procedure.
"This is a really difficult decision to make. These devices involve long surgeries, and they don't restore anything close to normal vision. The more information patients have, the better," she said.
Loss of rods and cones is the primary cause of vision loss in diseases such as macular degeneration or retinitis pigmentosa.
But those diseases leave most remaining neurons within the retina relatively intact, and various technologies under development aim to restore vision by targeting the surviving cells.
Two of the most promising devices, Fine said, are electric prostheses, which enable vision by stimulating surviving cells with an array of electrodes placed on the retina, and optogenetics, which insert proteins into the surviving retinal cells to make them light-sensitive.
But the devices have a major shortcoming, co-author Geoffrey Boynton said, since stimulating the surviving cells in a retina is unlikely to produce vision that is close to normal.
"The retina contains a vast diversity of cells that carry distinct visual information and respond differently to visual input," said Boynton, a UW psychology professor.
"Electrically stimulating the retina excites all of these cells at the same time, which is very different from how these cells respond to real visual input," he said.
There are similar issues with optogenetics, Boynton said.
"The optogenetic proteins that are currently available produce sluggish responses over time, and they are limited in the number of different cell types that they can separately target," he said.
These limitations in both technologies mean that patients may see fuzzy, comet-like shapes or blurred outlines, or they may experience temporary visual disappearances if an object moves too fast, researchers said.
The research was published in the journal Philosophical Transactions B.
