A cure for blindness is a step closer thanks to research into tadpoles which revealed the forces which can snap light sensing cells.
The experimental and theoretical findings, published in the Biophysical Journal, help explain the origin of severe eye diseases and could lead to better treatments.
Eye cells rely on their outer segment to convert light into brain signals that allow us to see, but because of its unique cylindrical shape, the outer segment is prone to breakage, which can cause blindness in humans.
Dr Aphrodite Ahmadi, of the State University of New York College at Cortland, said: ‘To our knowledge, this is the first theory that explains how the structural rigidity of the outer segment can make it prone to damage.
‘Our theory represents a significant advance in our understanding of retinal degenerative diseases.’
The outer segment of photoreceptors consists of discs packed with a light-sensitive protein called rhodopsin.
Discs made at night-time are different from those produced during the day, generating a banding pattern that was first observed in frogs but is common across species.
Mutations that affect photoreceptors often destabilise the outer segment and may damage its discs, leading to cell death, retinal degeneration and blindness in humans.
But until now, it was unclear which structural properties of the outer segment determine its susceptibility to damage.
Dr Ahmadi and her team examined tadpole photoreceptors under the microscope while subjecting them to fluid forces.
They found high-density bands packed with a high concentration of rhodopsin were very rigid, which made them more susceptible to breakage than low-density bands consisting of less rhodopsin.
Their model confirmed their experimental results and revealed factors that determine the critical force needed to break the outer segment.
The findings support the idea mutations causing rhodopsin to aggregate can destabilise the outer segment, eventually causing blindness.
Dr Ahmadi added: ‘Further refinement of the model could lead to novel ways to stabilize the outer segment and could delay the onset of blindness.’