Modelling studies have uncovered a surprising simplicity behind the development of the lens in mouse eyes, revealing insights that could help prevent and treat cataracts in humans. A lack of flexibility in the human eye lens, which can lead to cataracts, affects almost everyone over the age of 50.
The eye’s lens is our window on the world. It can effortlessly produce sharp images of objects at varying distances. However, how biological growth processes achieve this impressive optical precision remains as a big challenge for science.
In response, back in 2014, researchers based in Croatia and the United States drew on existing knowledge of the well-studied mouse eye to create mathematical simulations.
These modelled the behaviour of individual cells to show the lens grows and changes throughout an animal’s life. Their research shows that as cells multiply along the edges of the eye, they ‘push’ other recently formed cells inwards.
Surprisingly, their simulations predicted that lens growth depends on only two variables: the area in the lens occupied by each cell and the different rates of cell division in each of the four zones in the outer skin of the lens.
This simple two-variable model is the first to fully replicate lens growth over the entire lifespan of a mouse. It also helps explain how an essentially random process of cell division can produce a lens with the correct shape with an extremely high degree of accuracy.
The simulations also suggest how cataracts form in the lens during ageing.
They now believe that exposure to ultraviolet radiation in sunlight can cause mutations in lens cells, leading to the clouding associated with cataracts.
The model already explains how lenses become stiffer as we approach middle age, an issue that underlies most older peoples’ need for reading glasses as it is more difficult for them to adjust focus.
The researchers say this is historically the first ever mathematical model of the growth process of the eye lens. If some of their hypotheses about cataract development also prove to be correct for human lenses, then this may lead to methods to reduce cataracts, which in some underdeveloped countries is still the main cause of blindness.