Clearer vision

US researchers are making progress towards developing artificial eye lenses by using polymers and artificial proteins. These lenses could be used to treat cataract sufferers and provide a cure for age-related sight degeneration.

The model lens has been developed by Nathan Ravi, associate professor of ophthalmology and visual sciences at Washington University, and colleagues. Ravi’s approach replaces the gel-like material of the natural lens with an artificial equivalent. The natural lens is removed leaving the surrounding lens bag intact. A solution of artificial gel is then injected and cured.

Ravi’s first model, an acrylamide hydrogel had similar properties to a natural lens but it could not be used because osmotic pressure would cause the gel to swell. However a composite gel, a polyacrylamide derivative with artificial proteins, gave much better results. ’We have jumped the major hurdle,’ says Ravi. ’One does not have the worry of osmotic swelling.’

The artifical lens must behave like a young eye, be non-toxic with similar optical properties. The elastic properties also need to be comparable as a natural lens has a relaxation time of around 50ms.

There are alternative strategies. Jacqueline de Groot, manager of contract research at ophthalmological contract research company Orteq in the Netherlands, said that ’the only way to develop an injectable system is to use transparent lattices’. This method uses a polymer core with a high refractive index and a water soluble polymer shell.

Artificial lenses could restore the sight of many. ’With an ageing population this is a global issue,’ says Ravi.

Vikki Allen